JDBC Developer's Guide and Reference

Oracle® Database

21c

F31913-10

September 2022

Oracle Database JDBC Developer's Guide and Reference, 21c

F31913-10

Primary Author: Tulika Das

Contributing Authors: Brian Martin, Venkatasubramaniam Iyer, Elizabeth Hanes Perry, Brian Wright,

Thomas Pfaeffle

Contributors: Kuassi Mensah, Douglas Surber, Paul Lo, Ed Shirk, Tong Zhou, Jean de Lavarene, Rajkumar

Irudayaraj, Ashok Shivarudraiah, Nirmala Sundarappa, Angela Barone, Rosie Chen, Sunil Kunisetty, Joyce

Yang, Mehul Bastawala, Luxi Chidambaran, Vidya Nayak, Srinath Krishnaswamy, Swati Rao, Pankaj Chand,

Aman Manglik, Longxing Deng, Magdi Morsi, Ron Peterson, Ekkehard Rohwedder, Catherine Wong, Scott

Urman, Jerry Schwarz, Steve Ding, Soulaiman Htite, Anthony Lai, Prabha Krishna, Ellen Siegal, Susan Kraft,

Sheryl Maring

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Contents

Preface

Audience xxiv

Documentation Accessibility xxiv

See Also:

Support for Token-Based Authentication

• Java Data Source for Sharded Databases Access

See Also:

Overview of the Sharding Data Source

• JDBC Reactive Extensions

1-1

See Also:

JDBC Reactive Extensions

• Java Library for Reactive Streams Ingestion

See Also:

Support for Java library for Reactive Streams Ingestion

• Support for New JSON Data Type

See Also:

Package oracle.sql.json

• Compatibility with Client Libraries Prior to Release 21c

See Also:

Package oracle.sql.json

Deprecated Features

Deprecation of Older Encryption Algorithms

Starting with Oracle Database 21c, older encryption and hashing algorithms are

deprecated.

The deprecated algorithms for

DBMS_CRYPTO

and native network encryption include

MD4, MD5, DES, 3DES, and RC4-related algorithms as well as 3DES for Transparent

Data Encryption (TDE). Removing older, less secure cryptography algorithms prevents

accidental use of these algorithms. To meet your security requirements, Oracle

recommends that you use more modern cryptography algorithms, such as the

Advanced Encryption Standard (AES).

See Also:

Oracle Database Security Guide

1.2 Overview of Oracle JDBC Drivers

In addition to supporting the standard JDBC application programming interfaces

(APIs), Oracle drivers have extensions to support Oracle-specific data types and to

enhance performance.

Oracle provides the following JDBC drivers:

• Thin driver

Chapter 1

Overview of Oracle JDBC Drivers

1-2

The JDBC Thin driver is a pure Java, Type IV driver that can be used in applications. It is

platform-independent and does not require any additional Oracle software on the client-

side. The JDBC Thin driver communicates with the server using Oracle Net Services to

access Oracle Database.

The JDBC Thin driver enables a direct connection to the database by providing an

implementation of Oracle Net Services on top of Java sockets. The driver supports the

TCP/IP protocol and requires a TNS listener on the TCP/IP sockets on the database

server.

Note:

Oracle recommends you to use the Thin driver unless you have a feature that is

supported only by a specific driver.

• Oracle Call Interface (OCI) driver

It is used on the client-side with an Oracle client installation. It can be used only with

applications.

The JDBC OCI driver is a Type II driver used with Java applications. It requires platform-

specific OCI libraries. It supports all installed Oracle Net adapters, including interprocess

communication (IPC), named pipes, TCP/IP, and Internetwork Packet Exchange/

Sequenced Packet Exchange (IPX/SPX).

The JDBC OCI driver, written in a combination of Java and C, converts JDBC invocations

to calls to OCI, using native methods to call C-entry points. These calls communicate with

the database using Oracle Net Services.

The JDBC OCI driver uses the OCI libraries, C-entry points, Oracle Net, core libraries,

and other necessary files on the client computer where it is installed.

OCI is an API that enables you to create applications that use the native procedures or

function calls of a third-generation language to access Oracle Database and control all

phases of the SQL statement processing.

• Server-side Thin driver

It is functionally similar to the client-side Thin driver. However, it is used for code that runs

on the database server and needs to access another session either on the same server

or on a remote server on any tier.

The JDBC server-side Thin driver offers the same functionality as the JDBC Thin driver

that runs on the client-side. However, the JDBC server-side Thin driver runs inside Oracle

Database and accesses a remote database or a different session on the same database

for use with Java in the database.

This driver is useful in the following scenarios:

– Accessing a remote database server from an Oracle Database instance acting as a

middle tier

– Accessing an Oracle Database session from inside another, such as from a Java

stored procedure

The use of JDBC Thin driver from a client application or from inside a server does not

affect the code.

• Server-side internal driver

Chapter 1

Overview of Oracle JDBC Drivers

1-3

It is used for code that runs on the database server and accesses the same

session. That is, the code runs and accesses data from a single Oracle session.

The JDBC server-side internal driver supports any Java code that runs inside

Oracle Database, such as in a Java stored procedure, and accesses the same

database. It lets the Oracle Java Virtual Machine (Oracle JVM) to communicate

directly with the SQL engine for use with Java in the database.

The JDBC server-side internal driver, the Oracle JVM, the database, and the SQL

engine all run within the same address space, and therefore, the issue of network

round-trips is irrelevant. The programs access the SQL engine by using function

calls.

Note:

The server-side internal driver does not support the

cancel

and

setQueryTimeout

methods of the

Statement

class.

The JDBC server-side internal driver is fully consistent with the client-side drivers

and supports the same features and extensions.

The following figure illustrates the architecture of Oracle JDBC drivers and Oracle

Database.

Figure 1-1 Architecture of Oracle JDBC Drivers and Oracle Database

Oracle Database

JDBC Thin Driver

Java Sockets

OCI C Library

JDBC OCI Driver

SOL Engine

PL/SQL Engine

Java Engine

Server-Side Thin Driver

JDBC Server-Side

Internal Driver

KPRB C Library

Oracle Database

Related Topics

• Features Specific to JDBC Thin

Chapter 1

Overview of Oracle JDBC Drivers

1-4

• Features Specific to JDBC OCI Driver

• Server-Side Internal Driver

1.3 Choosing the Appropriate Driver

Consider the following when choosing a JDBC driver for your application or applet:

• In general, unless you need OCI-specific features, such as support for non-TCP/IP

networks, use the JDBC Thin driver.

• If you want maximum portability and performance, then use the JDBC Thin driver. You

can connect to Oracle Database from an application using the JDBC Thin driver.

• If you want to use Lightweight Directory Access Protocol (LDAP) over Secure Sockets

Layer (SSL)/Transport Layer Security (TLS), then use the JDBC Thin driver.

• If you are writing a client application for an Oracle client environment and need OCI-

driver-specific features, such as support for non-TCP/IP networks, then use the JDBC

OCI driver.

• For code that runs in the database server and needs to access a remote database or

another session within the same database instance, use the JDBC server-side Thin

driver.

• If your code runs inside the database server and needs to access data locally within the

session, then use the JDBC server-side internal driver to access that server.

1.4 Use Cases of Oracle JDBC Drivers

This section describes the use cases for Oracle JDBC drivers.

JDBC Thin Driver or Type 4 Client Driver

You must use the JDBC Thin driver in your client-side Java applications for accessing Oracle

Database over the TCP/IP protocol, for both

tcp

and

tcps

. This is the most widely used

driver that Oracle recommends to use because it offers a range of features as mentioned in

the following non-exhaustive list:

• Row count per iteration

• Support for promoting a local transaction to a global transaction

• Transaction Guard

• Transparent Application Continuity and Application Continuity

• Support for the Reactive Streams Ingestion library

• JDBC Reactive Extensions

See Also:

Feature List

Chapter 1

Choosing the Appropriate Driver

1-5

JDBC OCI Driver or Type 2 Client Driver

You must use the JDBC OCI driver in your client-side Java applications only if your

applications use any of the following features that are dependent on the platform-

specific OCI libraries:

• Bequeath protocol

This procol lets you use the local connections without going through the listener,

which is typically used by the Database Administrators to perform various

administrative operations; however, other non-administrative users too can use

this protocol.

See Also:

Using Bequeath Connection and SYS Logon

• OS Authentication

The JDBC OCI driver supports OS Authentication on Linux when the client and the

server are on the same computer. On Window domains, it supports OS

Authentication even across multiple computers.

• Transparent Application Failover (TAF) that supports failover of read transactions.

See Also:

Application Continuity for Java for information about complete high

availability features

Server-Side Internal Driver or Type 2 Server-Side Driver

You must use this driver for Java code that runs on the JVM embedded in the

Database server and accesses the same Database session. It means that the code

runs and accesses data from a single Database session. This driver is also known as

the JDBC KPRB Driver.

This driver is built in the JVM embedded in the Database, also known as Oracle JVM,

and it is not a fully-featured driver.

Server-Side Thin Driver or Type 4 Server-Side Driver

You must use this driver in the following scenarios:

• For accessing a remote database server from an Oracle Database instance acting

as a middle tier

• For accessing an Oracle Database session from within another session, such as

from a Java stored procedure

This driver is built in the Oracle JVM, and it is not a fully-featured driver.

Chapter 1

Use Cases of Oracle JDBC Drivers

1-6

1.5 Feature Differences Between JDBC OCI and Thin Drivers

The following table lists the features that are specific either to the JDBC OCI or the JDBC

Thin driver in Oracle Database Release 21c.

Table 1-1 Feature Differences Between the JDBC OCI Driver and the JDBC Thin

Driver

JDBC OCI Driver JDBC Thin Driver

OCI connection pooling NA

Transparent Application Failover (TAF) NA

NA Support for row count per iteration for array DML

NA SHA-2 Support in Oracle Advanced Security

oraaccess.xml

configuration file settings NA

NA Oracle Advanced Queuing

NA Support for the

O7L_MR

client ability

NA Support for promoting a local transaction to a

global transaction

NA Java Data Source for Sharded Databases Access

NA Java Library for Reactive Streams Ingestion

NA JDBC Reactive Extensions

NA Native JSON Type Support

Note:

• The OCI optimized fetch feature is internal to the JDBC OCI driver and not

applicable to the JDBC Thin driver.

• Some JDBC OCI driver features, inherited from the OCI library, are not

available in the Thin JDBC driver.

1.6 Environments and Support

This section provides a brief description of the tools and environments that you need to run a

JDBC application.

• Supported JDK and JDBC Versions

• JNI and Java Environments

• JDBC and IDEs

• Availability on Maven Central

Chapter 1

Feature Differences Between JDBC OCI and Thin Drivers

1-7

1.6.1 Supported JDK and JDBC Versions

In Oracle Database 21c, all the JDBC drivers are compatible with JDK 8, JDK 11, JDK

12, JDK 13, JDK 14, and JDK 15, and the

ojdbc8.jar

and

ojdbc11.jar

files provide

the support to these JDK versions.

When to Use ojdbc8.jar File

Use the

ojdbc8.jar

file when you want JDBC 4.2 features and need to compile your

code with JDK 8, JDK11, JDK12, JDK13, JDK14, and JDK15.

When to Use ojdbc11.jar File

Use the

ojdbc11.jar

file when you want JDBC 4.3 features and need to compile your

code with JDK 11, JDK 12, JDK13, JDK14, and JDK15.

Related Topics

• RDBMS and JDK Version Compatibility for Oracle JDBC Drivers

Oracle Database Release 21c JDBC drivers are certified with all supported Oracle

Database releases (21c, 19c, 18c, 12c, and 11g Release 2). However, they are not

certified to work with older, unsupported database releases, such as 10g and 9i.

See Also:

JDBC FAQ Page

1.6.2 JNI and Java Environments

The JDBC OCI driver uses the standard Java Native Interface (JNI) to call OCI C

libraries. You can use the JDBC OCI driver with Java Virtual Machines (JVMs), in

particular, with Microsoft and IBM JVMs.

1.6.3 JDBC and IDEs

The Oracle JDeveloper Suite provides developers with a single, integrated set of

products to build, debug, and deploy component-based database applications for the

Internet. The Oracle JDeveloper environment contains integrated support for JDBC,

including the JDBC Thin driver and the native OCI driver. The database component of

Oracle JDeveloper uses the JDBC drivers to manage the connection between the

application running on the client and the server.

1.6.4 Availability on Maven Central

All supported releases of the Oracle JDBC drivers, including 21.1.0.0, 19.9.0.0,

19.8.0.0, 19.6.0.0, 19.3.0.0, and 18.3.0.0, are available on Maven Central. So, you can

Chapter 1

Environments and Support

1-8

consider Maven Central as a distribution center for the Oracle JDBC drivers and companion

JAR files.

Group IDs for JDBC Drivers and Companion JAR Files on Maven Central

All Oracle Database artifacts on Maven Central reside under the same umbrella

com.oracle.database

as shown in the following image:

You can find the Oracle Database Artifacts under their specific focus area. For example,

JDBC, XML, security, high-availability (HA), NLS, observability, and so on. The following table

lists the group IDs of the JDBC drivers and the companion JAR files:

Group ID Corresponding JAR Files

com.oracle.database.jdbc ojdbc11.jar

ojdbc10.jar

ojdbc8.jar

ojdbc6.jar

ojdbc5.jar

ucp.jar

ojdbc10dms.jar

ojdbc8dms.jar

ojdbc6dms.jar

ojdbcd5dms.jar

com.oracle.database.jdbc.debug ojdbc11_g.jar

ojdbc10_g.jar

ojdbc8_g.jar

ojdbc6_g.jar

ojdbc5_g.jar

ojdbc11dms_g.jar

ojdbc10dms_g.jar

ojdbc8dms_g.jar

ojdbc6dms_g.jar

ojdbc5dms_g.jar

com.oracle.database.security osdt_core.jar

osdt_cert.jar

oraclepki.jar

com.oracle.database.ha ons.jar

simplefan.jar

com.oracle.database.nls orai18n.jar

com.oracle.database.xml xdb.jar

xdb6.jar

xmlparserv2.jar

com.oracle.database.observability dms.jar

Chapter 1

Environments and Support

1-9

Note:

• The

ojdbc8dms.jar

and

ojdbc11dms.jar

files provide complete support

for the Dynamic Monitoring System (DMS) and limited support for the

java.util.logging

package.

•

xdb6.jar

is a legacy name. The new name is

xdb.jar

Managing Dependencies on Maven Central with GAVs

You can manage the JDBC and UCP dependencies in the

pom.xml

file of your project

by using the corresponding group ID, artifact ID, and the version (GAV), as defined in

this section. For example, the following GAV pulls the

ojdbc10.jar

ucp.jar

oraclepki.jar

osdt_core.jar

osdt_cert.jar

ons.jar

, and

simplefan.jar

from

the 19.3 release:

<groupId>com.oracle.database.jdbc</groupId>

<artifactId>ojdbc10</artifactId>

</dependency>

Similarly, the following GAV pulls the

orai18n.jar

file from the 19.3.0.0 release:

<groupId>com.oracle.database.nls</groupId>

</dependency>

See Also:

JDBC FAQ Page

1.7 Feature List

This section lists the supported features and the corresponding versions in which they

were first supported in the JDBC OCI driver and the JDBC Thin driver.

Table 1-2 Feature List

Feature JDBC OCI JDBC Thin

TimeZone Patching 11.2 11.2

Secure LOB Support 11.2 11.2

LOB prefetch Support 11.2 11.2

Network Connection Pool NA 11.2

Chapter 1

Feature List

1-10

Table 1-2 (Cont.) Feature List

Feature JDBC OCI JDBC Thin

Column Security Support NA 11.2

XMLType Queue Support (AQ) NA 11.2

Notification Grouping (AQ and DCN) NA 11.2

SimpleFAN 11.2 11.2

Application Continuity 12.2 12.1

Transaction Guard 12.2 12.1

SQL Statement Translation NA 12.1

Database Resident Connection Pooling 12.1 12.1

SHA-2 Support in Oracle Advanced Security NA 12.1

Invisible Columns Support 12.1 12.1

Support for PL/SQL Package Types as Parameters 12.1 12.1

Support for Monitoring of Database Operations 12.1 12.1

Support for Increased Length Limit for Various Data

Types

12.1 12.1

Implicit Results Support 12.1 12.1

Support for row count per iteration for array DML NA 12.1

oraaccess.xml

configuration file settings 12.1 NA

Transparent Application Continuity NA 18c

Support for verifying JSON Data 18c 18c

Support for Lightweight Connection Validation NA 18c

Support for REF CURSOR as IN bind variables 18c 18c

Support for Key Store Service NA 18c

Easy Connect Plus (Easy Connect Naming Syntax

Improvements)

NA 19c

Java Library for Reactive Streams Ingestion NA 21c

Java Data Source for Sharded Databases Access NA 21c

JDBC Support for Native JSON Data Type NA 21c

JDBC Reactive Extensions NA 21c

Chapter 1

Feature List

1-11

Note:

• The following features of JDBC drivers were introduced in releases

earlier than release 11.2:

– NLS Support

– New Statement Caching API

– Row Prefetch

– Java Native Interface

– Native LOB

– Associative Arrays/index-by-table

– Implicit Statement Caching

– Explicit Statement Caching

– Temporary LOBs

– Object Type Inheritance

– Multilevel Collections

–

oracle.jdbc

Interfaces

– Native XA

– OCI Connection Pooling

– Transparent Application Failover

– Implicit Connection Cache

– Fast Connection Failover

– Connection Wrapping

– DMS

– Service Names in URLs

– Set Statement Parameters by Name

– End-to-End Tracing

– Web

RowSet

– Proxy Authentication

– Run-time Connection Load Balancing

– Extended

setXXX

and

getXXX

methods for LOBs

– XA Connection Cache

– DML Returning

– JSR 114

RowSets

– SSL/TLS Encryption

– SSL/TLS Authentication

– AES Encryption

– SHA1 Hash

Chapter 1

Feature List

1-12

– Radius Authentication

– Kerberos Authentication

–

ANYDATA

and

ANYTYPE

types

– Native AQ

– Query Change Notification

– Database start up and shut down

– Factory methods for data types

– Buffer Cache

– Secure File LOBs

– Diagnosability

– Server Result Cache

– Universal Connection Pool

• The

ConnectionCacheImpl

connection cache feature is deprecated since

Oracle Database 10g.

• The Implicit Connection Cache feature is desupported now.

Chapter 1

Feature List

1-13

Getting Started

This chapter discusses the compatibility of Oracle Java Database Connectivity (JDBC) driver

versions, database versions, and Java Development Kit (JDK) versions. It also describes the

basics of testing a client installation and configuration and running a simple application. This

chapter contains the following sections:

• Version Compatibility for Oracle JDBC Drivers

• Verifying a JDBC Client Installation

• Basic Steps in JDBC

• Sample: Connecting_ Querying_ and Processing the Results

• Support for Invisible Columns

• Support for Verifying JSON Data

• Support for Implicit Results

• Support for Lightweight Connection Validation

• Support for Deprioritization of Database Nodes

• Support for Oracle Connection Manager in Traffic Director Mode

• Stored Procedure Calls in JDBC Programs

• About Processing SQL Exceptions

2.1 RDBMS and JDK Version Compatibility for Oracle JDBC

Drivers

Oracle Database Release 21c JDBC drivers are certified with all supported Oracle Database

releases (21c, 19c, 18c, 12c, and 11g Release 2). However, they are not certified to work with

older, unsupported database releases, such as 10g and 9i.

The following table describes the JDBC and Oracle Database interoperability matrix or the

certification matrix:

JDBC Driver

Version

Database 21.x Database 19.x Database 18.3 Database 12.2

and 12.1

Database

11.2.0.4

JDBC 21.x Yes Yes Yes Yes Yes

JDBC 19.x Yes Yes Yes Yes Yes

JDBC 18.3 Yes Yes Yes Yes Yes

JDBC 12.2 and

12.1

Yes Yes Yes Yes Yes

JDBC 11.2.0.4 Yes Yes Yes Yes Yes

Oracle JDBC Drivers are always compliant to the latest JDK version for every new release.

For some versions, JDBC drivers support multiple JDK versions. The following table

2-1

describes the release-specific JDBC JAR files and supported JDK versions for various

Oracle Database versions:

Oracle Database Version Release-Specific JDBC JAR File with

Supported JDK Version

21.x

ojdbc11.jar

with JDK 11, JDK 12, JDK 13,

JDK 14 and JDK 15

ojdbc8.jar

with JDK 8, JDK 11, JDK 12,

JDK 13, JDK 14 and JDK 15

19.x

ojdbc10.jar

with JDK 10, JDK 11

ojdbc8.jar

with JDK 8, JDK 9, JDK 11

18.3

ojdbc8.jar

with JDK 8, JDK 9, JDK 10, JDK

12.2 or 12cR2

ojdbc8.jar

with JDK 8

12.1 or 12cR1

ojdbc7.jar

with JDK 7, JDK 8

ojdbc6.jar

with JDK 6

11.2 or 11gR2

ojdbc6.jar

with JDK 6, JDK 7, JDK 8

ojdbc5.jar

with JDK 5

Related Topics

• Oracle Universal Connection Pool Developer’s Guide

• Oracle JDBC FAQ

2.2 Verifying a JDBC Client Installation

This section describes the steps that you must perform to verify a JDBC client

installation.

• Checking the Installed Directories and Files

• Checking the Environment Variables

• Ensuring that the Java Code Can Be Compiled and Run

• Determining the Version of the JDBC Driver

• Testing the JDBC and Database Connection

This section describes the steps for verifying an Oracle client installation of the JDBC

drivers, assuming that you have already installed the driver of your choice. Installation

of an Oracle JDBC driver is platform-specific. You must follow the installation

instructions for the driver you want to install in your platform-specific documentation.

If you use the JDBC Thin driver, then there is no additional installation on the client

computer. If you use the JDBC Oracle Call Interface (OCI) driver, then you must also

install the Oracle client software. This includes Oracle Net and the OCI libraries.

Note:

The JDBC Thin driver requires a TCP/IP listener to be running on the

computer, where the database is installed.

Chapter 2

Verifying a JDBC Client Installation

2-2

2.2.1 Checking the Installed Directories and Files

Installing the Oracle Java products creates the directories described in this section, among

other things.

•

ORACLE_HOME/jdbc

•

ORACLE_HOME

/jlib

Check whether or not the following directories and files have been created and populated in

the

ORACLE_HOME/jdbc

directory:

•

doc

This directory contains the

javadoc.zip

file, which is the Oracle JDBC application

programming interface (API) documentation.

•

lib

The

lib

directory contains the following required Java classes:

–

orai18n.jar

and

orai18n-mapping.jar

Contain classes for globalization and multibyte character sets support

–

ojdbc11.jar

and

ojdbc11_g.jar

Contain the JDBC driver classes for use with JDK 11

–

rsi.jar

Contains the library for Reactive Streams Ingestion support

See Also:

Support for Java library for Reactive Streams Ingestion

•

Readme.txt

This file contains late-breaking and release-specific information about the drivers, which

may not have been included in other documentation on the product.

Check whether or not the following directories have been created and populated in the

ORACLE_HOME

/jlib

directory:

•

jta.jar

and

jndi.jar

These files contain classes for the Java Transaction API (JTA) and the Java Naming and

Directory Interface (JNDI). These are required only if you are using JTA features for

distributed transaction management or JNDI features for naming services.

•

ons.jar

This JAR file contains classes for Oracle RAC Fast Application Notification. It is also

required for Universal Connection Pool (UCP) features like Fast Connection Failover,

Run-time Load Balancing, Web Session Affinity, and Transaction Affinity.

Related Topics

• Oracle RAC Fast Application Notification

• jta.jar

Chapter 2

Verifying a JDBC Client Installation

2-3

• jndi.jar

• Oracle Universal Connection Pool Developer’s Guide

2.2.2 Checking the Environment Variables

This section describes the environment variables that must be set for the JDBC OCI

driver and the JDBC Thin driver, focusing on Solaris, Linux, and Microsoft Windows

platforms.

You must set the

CLASSPATH

environment variable for JDBC OCI or Thin driver. Include

the following in the

CLASSPATH

environment variable:

ORACLE_HOME/jdbc/lib/ojdbc11.jar

ORACLE_HOME/jlib/orai18n.jar

Note:

If you use the JTA features and the JNDI features, then you must specify

jta.jar

and

jndi.jar

in your

CLASSPATH

environment variable.

JDBC OCI Driver

To use the JDBC OCI driver, you must also set the following value for the library path

environment variable:

• On Solaris or Linux, set the

LD_LIBRARY_PATH

environment variable as follows:

ORACLE_HOME/lib

This directory contains the

libocijdbc11.so

shared object library.

• On Microsoft Windows, set the

PATH

environment variable as follows:

ORACLE_HOME\bin

This directory contains the

ocijdbc11.dll

dynamic link library.

All of the JDBC OCI demonstration programs can be run in the Instant Client mode by

including the JDBC OCI Instant Client data shared library on the library path

environment variable.

JDBC Thin Driver

To use the JDBC Thin driver, you do not have to set any other environment variables.

However, to use the JDBC server-side Thin driver, you need to set permission.

Setting Permission for the Server-Side Thin Driver

The JDBC server-side Thin driver opens a socket for its connection to the database.

Because Oracle Database enforces the Java security model, a check is performed for

SocketPermission

object.

To use the JDBC server-side Thin driver, the connecting user must be granted the

appropriate permission. The following is an example of how the permission can be

granted for the user

Chapter 2

Verifying a JDBC Client Installation

2-4

CREATE ROLE jdbcthin;

CALL dbms_java.grant_permission('JDBCTHIN', 'java.net.SocketPermission', '*',

'connect');

GRANT jdbcthin TO HR;

Note that

JDBCTHIN

in the

grant_permission

call must be in uppercase. The asterisk (

) is a

pattern. You can restrict the user by granting permission to connect to only specific

computers or ports.

Related Topics

• Features Specific to JDBC OCI Driver

• Oracle Database Java Developer’s Guide

2.2.3 Ensuring that the Java Code Can Be Compiled and Run

To further ensure that Java is set up properly on your client system, go to the

samples

directory under the

ORACLE_HOME/jdbc/demo

directory. Now, type the following commands on

the command line, one after the other, to see if the Java compiler and the Java interpreter run

without error:

javac

java

Each of the preceding commands should display a list of options and parameters and then

exit. Ideally, verify that you can compile and run a simple test program, such as

jdbc/demo/

samples/generic/SelectExample

2.2.4 Determining the Version of the JDBC Driver

To determine the version of the JDBC driver, call the

getDriverVersion

method of the

OracleDatabaseMetaData

class as shown in the following sample code:

import java.sql.*;

import oracle.jdbc.*;

import oracle.jdbc.pool.OracleDataSource;

class JDBCVersion

{

public static void main (String args[]) throws SQLException

{

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:thin:HR/hr@<host>:<port>:<service>");

Connection conn = ods.getConnection();

// Create Oracle DatabaseMetaData object

DatabaseMetaData meta = conn.getMetaData();

// gets driver info:

System.out.println("JDBC driver version is " + meta.getDriverVersion());

}

You can also determine the version of the JDBC driver by executing the following commands:

•

java -jar ojdbc8.jar

Chapter 2

Verifying a JDBC Client Installation

2-5

•

java -jar ojdbc11.jar

2.2.5 Testing the JDBC and Database Connection

The

samples

directory contains sample programs for a particular Oracle JDBC driver.

One of the programs,

JdbcCheckup.java

, is designed to test JDBC and the database

connection. The program queries for the user name, password, and the name of the

database to which you want to connect. The program connects to the database,

queries for the string "

Hello World

", and prints it to the screen.

Go to the

samples

directory, and compile and run the

JdbcCheckup.java

program. If

the results of the query print without error, then your Java and JDBC installations are

correct.

Although

JdbcCheckup.java

is a simple program, it demonstrates several important

functions by performing the following:

• Imports the necessary Java classes, including JDBC classes

• Creates a

DataSource

instance

• Connects to the database

• Runs a simple query

• Prints the query results to your screen

The

JdbcCheckup.java

program, which uses the JDBC OCI driver, is as follows:

* This sample can be used to check the JDBC installation.

* Just run it and provide the connect information. It will select

* "Hello World" from the database.

// You need to import the java.sql and JDBC packages to use JDBC

import java.sql.*;

import oracle.jdbc.*;

import oracle.jdbc.pool.OracleDataSource;

// We import java.io to be able to read from the command line

import java.io.*;

class JdbcCheckup

{

public static void main(String args[]) throws SQLException, IOException

{

// Prompt the user for connect information

System.out.println("Please enter information to test connection to

the database");

String user;

String password;

String database;

user = readEntry("user: ");

int slash_index = user.indexOf('/');

if (slash_index != -1)

{

password = user.substring(slash_index + 1);

user = user.substring(0, slash_index);

Chapter 2

Verifying a JDBC Client Installation

2-6

}

else

password = readEntry("password: ");

database = readEntry("database(a TNSNAME entry): ");

System.out.print("Connecting to the database...");

System.out.flush();

System.out.println("Connecting...");

// Open an OracleDataSource and get a connection

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:oci:@" + database);

ods.setUser(user);

ods.setPassword(password);

Connection conn = ods.getConnection();

System.out.println("connected.");

// Create a statement

Statement stmt = conn.createStatement();

// Do the SQL "Hello World" thing

ResultSet rset = stmt.executeQuery("select 'Hello World' from dual");

while (rset.next())

System.out.println(rset.getString(1));

// close the result set, the statement and the connection

rset.close();

stmt.close();

conn.close();

System.out.println("Your JDBC installation is correct.");

}

// Utility function to read a line from standard input

static String readEntry(String prompt)

{

try

{

StringBuffer buffer = new StringBuffer();

System.out.print(prompt);

System.out.flush();

int c = System.in.read();

while (c != '\n' && c != -1)

{

buffer.append((char)c);

c = System.in.read();

}

return buffer.toString().trim();

}

catch(IOException e)

{

return "";

}

2.3 Basic Steps in JDBC

After verifying the JDBC client installation, you can start creating your JDBC applications.

When using Oracle JDBC drivers, you must include certain driver-specific information in your

programs. This section describes, in the form of a tutorial, where and how to add the

Chapter 2

Basic Steps in JDBC

2-7

information. The tutorial guides you through the steps to create code that connects to

and queries a database from the client.

You must write code to perform the following tasks:

1. Importing Packages

2. Opening a Connection to a Database

3. Creating a Statement Object

4. Running a Query and Retrieving a Result Set Object

5. Processing the Result Set Object

6. Closing the Result Set and Statement Objects

7. Making Changes to the Database

8. About Committing Changes

9. Closing the Connection

Note:

You must supply Oracle driver-specific information for the first three tasks

that enable your program to use the JDBC application programming interface

(API) to access a database. For the other tasks, you can use standard JDBC

Java code, as you would for any Java application.

2.3.1 Importing Packages

Regardless of which Oracle JDBC driver you use, include the

import

statements

shown in Table 2-1 at the beginning of your program using the following syntax:

import <package_name>;

Table 2-1 Import Statements for JDBC Driver

Import statement Provides

import java.sql.*;

Standard JDBC packages.

import java.math.*;

The

BigDecimal

and

BigInteger

classes. You can

omit this package if you are not going to use these

classes in your application.

import oracle.jdbc.*;

import oracle.jdbc.pool.*;

import oracle.sql.*;

Oracle extensions to JDBC. This is optional.

OracleDataSource

Oracle type extensions. This is optional.

The Oracle packages listed as optional provide access to the extended functionality

provided by Oracle JDBC drivers, but are not required for the example presented in

this section.

Chapter 2

Basic Steps in JDBC

2-8

Note:

It is better to import only the classes your application needs, rather than using the

wildcard asterisk (

). This guide uses the asterisk (*) for simplicity, but this is not the

recommended way of importing classes and interfaces.

2.3.2 Opening a Connection to a Database

First, you must create an

OracleDataSource

instance. Then, open a connection to the

database using the

OracleDataSource.getConnection

method. The properties of the

retrieved connection are derived from the

OracleDataSource

instance. If you set the URL

connection property, then all other properties, including

TNSEntryName

DatabaseName

ServiceName

ServerName

PortNumber

Network Protocol

, and driver type are ignored.

Specifying a Database URL, User Name, and Password

The following code sets the URL, user name, and password for a data source:

OracleDataSource ods = new OracleDataSource();

ods.setURL(url);

ods.setUser(user);

ods.setPassword(password);

The following example connects user

with password

to a database with service

orcl

through port 5221 of the host

myhost

, using the JDBC Thin driver:

OracleDataSource ods = new OracleDataSource();

String url = "jdbc:oracle:thin:@//myhost:5221/orcl";

ods.setURL(url);

ods.setUser("HR");

ods.setPassword("hr");

Connection conn = ods.getConnection();

Note:

The user name and password specified in the arguments override any user name

and password specified in the URL.

Specifying a Database URL that Includes User Name and Password

The following example connects user

with password

to a database host whose

Transparent Network Substrate (TNS) entry is

myTNSEntry

, using the JDBC Oracle Call

Interface (OCI) driver. In this case, the URL includes the user name and password and is the

only input parameter.

String url = "jdbc:oracle:oci:HR/hr@myTNSEntry");

ods.setURL(url);

Connection conn = ods.getConnection();

If you want to connect using the Thin driver, then you must specify the port number. For

example, if you want to connect to the database on the host

myhost

that has a TCP/IP

listener on port 5221 and the service identifier is

orcl

, then provide the following code:

Chapter 2

Basic Steps in JDBC

2-9

String URL = "jdbc:oracle:thin:HR/hr@//myhost:5221/orcl");

ods.setURL(URL);

Connection conn = ods.getConnection();

Related Topics

• Data Sources and URLs

2.3.3 Creating a Statement Object

Once you connect to the database and, in the process, create a

Connection

object,

the next step is to create a

Statement

object. The

createStatement

method of the

JDBC

Connection

object returns an object of the JDBC

Statement

type. To continue

the example from the previous section, where the

Connection

object

conn

was

created, here is an example of how to create the

Statement

object:

Statement stmt = conn.createStatement();

2.3.4 Running a Query and Retrieving a Result Set Object

To query the database, use the

executeQuery

method of the

Statement

object. This

method takes a SQL statement as input and returns a JDBC

ResultSet

object.

Note:

• The method used to execute a

Statement

object depends on the type of

SQL statement being executed. If the

Statement

object represents a

SQL query returning a

ResultSet

object, the

executeQuery

method

should be used. If the SQL is known to be a DDL statement or a DML

statement returning an update count, the

executeUpdate

method should

be used. If the type of the SQL statement is not known, the

execute

method should be used.

• In case of a standard JDBC driver, if the SQL string being executed does

not return a

ResultSet

object, then the

executeQuery

method throws a

SQLException

exception. In case of an Oracle JDBC driver, the

executeQuery

method does not throw a

SQLException

exception even if

the SQL string being executed does not return a

ResultSet

object.

To continue the example, once you create the

Statement

object

stmt

, the next step is

to run a query that returns a

ResultSet

object with the contents of the

first_name

column of a table of employees named

EMPLOYEES

ResultSet rset = stmt.executeQuery ("SELECT first_name FROM employees");

2.3.5 Processing the Result Set Object

Once you run your query, use the

next()

method of the

ResultSet

object to iterate

through the results. This method steps through the result set row by row, detecting the

end of the result set when it is reached.

Chapter 2

Basic Steps in JDBC

2-10

To pull data out of the result set as you iterate through it, use the appropriate

getXXX

methods

of the

ResultSet

object, where

XXX

corresponds to a Java data type.

For example, the following code will iterate through the

ResultSet

object,

rset

, from the

previous section and will retrieve and print each employee name:

while (rset.next())

System.out.println (rset.getString(1));

The

next()

method returns

false

when it reaches the end of the result set. The employee

names are materialized as Java

String

values.

2.3.6 Closing the Result Set and Statement Objects

You must explicitly close the

ResultSet

and

Statement

objects after you finish using them.

This applies to all

ResultSet

and

Statement

objects you create when using Oracle JDBC

drivers. The drivers do not have finalizer methods. The cleanup routines are performed by the

method of the

ResultSet

and

Statement

classes. If you do not explicitly close the

ResultSet

and

Statement

objects, serious memory leaks could occur. You could also run out

of cursors in the database. Closing both the result set and the statement releases the

corresponding cursor in the database. If you close only the result set, then the cursor is not

released.

For example, if your

ResultSet

object is

rset

and your

Statement

object is

stmt

, then close

the result set and statement with the following lines of code:

rset.close();

stmt.close();

When you close a

Statement

object that a given

Connection

object creates, the connection

itself remains open.

Note:

Typically, you should put

statements in a

finally

clause.

2.3.7 Making Changes to the Database

DML Operations

To perform DML (Data Manipulation Language) operations, such as INSERT or UPDATE

operations, you can create either a

Statement

object or a

PreparedStatement

object.

PreparedStatement

objects enable you to run a statement with varying sets of input

parameters. The

prepareStatement

method of the JDBC

Connection

object lets you define a

statement that takes variable bind parameters and returns a JDBC

PreparedStatement

object

with your statement definition.

Use the

setXXX

methods on the

PreparedStatement

object to bind data to the prepared

statement to be sent to the database.

The following example shows how to use a prepared statement to run

INSERT

operations that

add two rows to the

EMPLOYEES

table.

Chapter 2

Basic Steps in JDBC

2-11

// Prepare to insert new names in the EMPLOYEES table

PreparedStatement pstmt = null;

try{

pstmt = conn.prepareStatement ("insert into EMPLOYEES (EMPLOYEE_ID,

FIRST_NAME) values (?, ?)");

// Add LESLIE as employee number 1500

pstmt.setInt (1, 1500); // The first ? is for EMPLOYEE_ID

pstmt.setString (2, "LESLIE"); // The second ? is for FIRST_NAME

// Do the insertion

pstmt.execute();

// Add MARSHA as employee number 507

pstmt.setInt (1, 507); // The first ? is for EMPLOYEE_ID

pstmt.setString (2, "MARSHA"); // The second ? is for FIRST_NAME

// Do the insertion

pstmt.execute();

}

finally{

if(pstmt!=null)

// Close the statement

pstmt.close();

}

DDL Operations

To perform data definition language (DDL) operations, you must create a

Statement

object. The following example shows how to create a table in the database:

//create table EMPLOYEES with columns EMPLOYEE_ID and FIRST_NAME

String query;

Statement stmt=null;

try{

query="create table EMPLOYEES " +

"(EMPLOYEE_ID int, " +

"FIRST_NAME varchar(50))";

stmt = conn.createStatement();

stmt.executeUpdate(query);

}

finally{

//close the Statement object

stmt.close();

}

Note:

You can also use a

PreparedStatement

object to perform DDL operations.

However, you should not use a

PreparedStatement

object because the

useful part of such an object is that it can have parameters and a DDL

operation does not have any parameters.

Also, due to a Database limitation, if you use a

PreparedStatement

object for

a DDL operation, then it only works for the first time it is executed. So, you

should use only

Statement

objects for DDL operations.

Chapter 2

Basic Steps in JDBC

2-12

The following example shows how to prepare your DDL statements before any reexecution:

Statement stmt = null;

PreparedStatement pstmt = null;

try{

pstmt = conn.prepareStatement ("insert into EMPLOYEES (EMPLOYEE_ID, FIRST_NAME)

values (?, ?)");

stmt = conn.createStatement("truncate table EMPLOYEES");

// Add LESLIE as employee number 1500

pstmt.setInt (1, 1500); // The first ? is for EMPLOYEE_ID

pstmt.setString (2, "LESLIE"); // The second ? is for FIRST_NAME

pstmt.execute();

stmt.executeUpdate();

// Add MARSHA as employee number 507

pstmt.setInt (1, 507); // The first ? is for EMPLOYEE_ID

pstmt.setString (2, "MARSHA"); // The second ? is for FIRST_NAME

pstmt.execute();

stmt.executeUpdate();

}

finally{

if(pstmt!=null)

// Close the statement

pstmt.close();

}

Related Topics

• The setObject and setOracleObject Methods

• Other setXXX Methods

2.3.8 About Committing Changes

By default, data manipulation language (DML) operations are committed automatically as

soon as they are run. This is known as the auto-commit mode. If auto-commit mode is on and

you perform a

COMMIT

ROLLBACK

operation using the

commit

rollback

method on a

connection object, then you get the following error messages:

Table 2-2 Error Messages for Operations Performed When Auto-Commit Mode is ON

Operation Error Messages

COMMIT Could not commit with auto-commit set on

ROLLBACK Could not rollback with auto-commit set on

If a SQLException is raised during a

COMMIT

ROLLBACK

operation with the error messages

as mentioned in the preceding table, then check the auto-commit status of the connection

because you get an exception when these operations are performed on a connection that has

auto-commit value set to

true

This exception is raised for any one of the following cases:

• When auto-commit status is set to

true

and

commit

rollback

method is called

Chapter 2

Basic Steps in JDBC

2-13

• When the default status of auto-commit is not changed and

commit

rollback

method is called

• When the value of the

COMMIT_ON_ACCEPT_CHANGES

property is

true

and

commit

rollback

method is called after calling the

acceptChanges

method on a rowset

However, you can disable auto-commit mode with the following method call on the

Connection

object:

conn.setAutoCommit(false);

If you disable the auto-commit mode, then you must manually commit or roll back

changes with the appropriate method call on the

Connection

object:

conn.commit();

or:

conn.rollback();

COMMIT

ROLLBACK

operation affects all DML statements run since the last

COMMIT

ROLLBACK

Note:

• If the auto-commit mode is disabled and you close the connection

without explicitly committing or rolling back your last changes, then an

implicit

COMMIT

operation is run.

• Any data definition language (DDL) operation always causes an implicit

COMMIT

. If the auto-commit mode is disabled, then this implicit

COMMIT

will

commit any pending DML operations that had not yet been explicitly

committed or rolled back.

Related Topics

• Disabling Auto-Commit Mode

2.3.8.1 Changing Commit Behavior

When a transaction updates the database, it generates a redo entry corresponding to

this update. Oracle Database buffers this redo in memory until the completion of the

transaction. When you commit the transaction, the Log Writer (LGWR) process writes

the redo entry for the commit to disk, along with the accumulated redo entries of all

changes in the transaction. By default, Oracle Database writes the redo to disk before

the call returns to the client. This behavior introduces latency in the commit because

the application must wait for the redo entry to be persisted on disk.

If your application requires very high transaction throughput and you are willing to

trade commit durability for lower commit latency, then you can change the behavior of

the default

COMMIT

operation, depending on the needs of your application. You can

change the behavior of the

COMMIT

operation with the following options:

•

WAIT

•

NOWAIT

Chapter 2

Basic Steps in JDBC

2-14

•

WRITEBATCH

•

WRITEIMMED

These options let you control two different aspects of the commit phase:

• Whether the

COMMIT

call should wait for the server to process it or not. This is achieved

by using the

WAIT

NOWAIT

option.

• Whether the Log Writer should batch the call or not. This is achieved by using the

WRITEIMMED

WRITEBATCH

option.

You can also combine different options together. For example, if you want the

COMMIT

call to

return without waiting for the server to process it and also the log writer to process the

commits in batch, then you can use the

NOWAIT

and

WRITEBATCH

options together. For

example:

((OracleConnection)conn).commit(

EnumSet.of(

OracleConnection.CommitOption.WRITEBATCH,

OracleConnection.CommitOption.NOWAIT));

Note:

you cannot use the

WAIT

and

NOWAIT

options together because they have opposite

meanings. If you do so, then the JDBC driver will throw an exception. The same

applies to the

WRITEIMMED

and

WRITEBATCH

options.

2.3.9 Closing the Connection

You must close the connection to the database after you have performed all the required

operations and no longer require the connection. You can close the connection by using the

method of the

Connection

object, as follows:

conn.close();

Note:

Typically, you should put

statements in a

finally

clause.

2.4 Sample: Connecting, Querying, and Processing the Results

The steps in the preceding sections are illustrated in the following example, which uses the

Oracle JDBC Thin driver to create a data source, connects to the database, creates a

Statement

object, runs a query, and processes the result set.

Note that the code for creating the

Statement

object, running the query, returning and

processing the

ResultSet

object, and closing the statement and connection uses the

standard JDBC API.

import java.sql.Connection;

import java.sql.ResultSet;

Chapter 2

Sample: Connecting, Querying, and Processing the Results

2-15

import java.sql.Statement;

import java.sql.SQLException;

import oracle.jdbc.pool.OracleDataSource;

class JdbcTest

{

public static void main (String args []) throws SQLException

{

OracleDataSource ods = null;

Connection conn = null;

Statement stmt = null;

ResultSet rset = null;

// Create DataSource and connect to the local database

ods = new OracleDataSource();

ods.setURL("jdbc:oracle:thin:@//localhost:5221/orcl");

ods.setUser("HR");

ods.setPassword("hr");

conn = ods.getConnection();

try

{

// Query the employee names

stmt = conn.createStatement ();

rset = stmt.executeQuery ("SELECT first_name FROM employees");

// Print the name out

while (rset.next ())

System.out.println (rset.getString (1));

}

//Close the result set, statement, and the connection

finally{

if(rset!=null) rset.close();

if(stmt!=null) stmt.close();

if(conn!=null) conn.close();

}

If you want to adapt the code for the OCI driver, then replace the call to the

OracleDataSource.setURL

method with the following:

ods.setURL("jdbc:oracle:oci:@MyHostString");

where,

MyHostString

is an entry in the

TNSNAMES.ORA

file.

2.5 Support for Invisible Columns

Starting from this release, Oracle Database supports invisible columns. Using this

feature, you can add a column to the table in hidden mode and make it visible later.

JDBC provides APIs to retrieve information about invisible columns. To get information

about whether a column is invisible or not, you can use the

isColumnInvisible

method available in the

oracle.jdbc.OracleResultSetMetaData

interface in the

following way:

Chapter 2

Support for Invisible Columns

2-16

Example

...

Connection conn = DriverManager.getConnection(jdbcURL, user, password);

Statement stmt = conn.createStatement ();

stmt.executeQuery ("create table hiddenColsTable (a varchar(20), b int invisible)");

stmt.executeUpdate("insert into hiddenColsTable (a,b ) values('somedata',1)");

stmt.executeUpdate("insert into hiddenColsTable (a,b) values('newdata',2)");

System.out.println ("Invisible columns information");

try

{

ResultSet rset = stmt.executeQuery("SELECT a, b FROM hiddenColsTable");

OracleResultSetMetaData rsmd = (OracleResultSetMetaData)rset.getMetaData();

while (rset.next())

{

System.out.println("column1 value:" + rset.getString(1));

System.out.println("Visibility:" + rsmd.isColumnInvisible(1));

System.out.println("column2 value:" + rset.getInt(2));

System.out.println("Visibility:" + rsmd.isColumnInvisible(2));

}

catch (Exception ex)

{

System.out.println("Exception :" + ex);

ex.printStackTrace();

}

Alternatively, you can also use the

getColumns

method available in the

oracle.jdbc.OracleDatabaseMetaData

class to retrieve information about invisible columns.

Example

...

Connection conn = DriverManager.getConnection(jdbcURL, user, password);

Statement stmt = conn.createStatement ();

stmt.executeQuery ("create table hiddenColsTable (a varchar(20), b int invisible)");

stmt.executeUpdate("insert into hiddenColsTable (a,b ) values('somedata',1)");

stmt.executeUpdate("insert into hiddenColsTable (a,b) values('newdata',2)");

System.out.println ("getColumns for table with invisible columns");

try

{

DatabaseMetaData dbmd = conn.getMetaData();

ResultSet rs = dbmd.getColumns(null, "HR", "hiddenColsTable", null);

OracleResultSetMetaData rsmd = (OracleResultSetMetaData)rs.getMetaData();

int colCount = rsmd.getColumnCount();

System.out.println("colCount: " + colCount);

String[] columnNames = new String [colCount];

for (int i = 0; i < colCount; ++i)

{

columnNames[i] = rsmd.getColumnName (i + 1);

}

while (rs.next())

{

for (int i = 0; i < colCount; ++i)

System.out.println(columnNames[i] +":" +rs.getString (columnNames[i]));

}

Chapter 2

Support for Invisible Columns

2-17

}

catch (Exception ex)

{

System.out.println("Exception: " + ex);

ex.printStackTrace();

}

Note:

The server-side internal driver,

kprb

does not support fetching information

about invisible columns.

2.6 Support for Verifying JSON Data

Starting from Oracle Database Release 18c, JDBC drivers can verify whether a

column returned in the

ResultSet

is a JSON column or not. To get information about

whether a column is JSON or not, you can use the

isColumnJSON

method available in

the

oracle.jdbc.OracleResultSetMetaData

interface in the following way:

Example 2-1 Example

...

public void test(Connection conn)

throws Exception{

try {

show ("tkpjb26776242 - start");

createTable(conn);

String sql = "SELECT col1, col2, col3, col4, col5, col6, col7,

col8 FROM tkpjb26776242_tab";

Statement stmt = conn.createStatement();

ResultSet rs = stmt.executeQuery(sql);

ResultSetMetaData rsmd = rs.getMetaData();

OracleResultSetMetaData orsmd = (OracleResultSetMetaData)rsmd;

int colCnt = orsmd.getColumnCount();

show("Table has " + colCnt + " columns.");

for (int i = 1; i <= colCnt; i++) {

String columnName = orsmd.getColumnName(i);

String typeName = orsmd.getColumnTypeName(i);

boolean invisible = orsmd.isColumnInvisible(i);

boolean json = orsmd.isColumnJSON(i);

show(columnName + " " + typeName + (invisible?"

INVISIBLE":"") + (json?" JSON":""));

}

rs.close();

stmt.close();

Chapter 2

Support for Verifying JSON Data

2-18

show ("tkpjb26776242 - end");

}

finally {

dropTable(conn);

}

private void createTable(Connection conn) throws Exception{

String sql = " create table tkpjb26776242_tab ( "

+ " col1 clob, "

+ " col2 clob , "

+ " col3 clob INVISIBLE, "

+ " col4 clob INVISIBLE, "

+ " col5 varchar2(200), "

+ " col6 varchar2(200), "

+ " col7 varchar2(200) INVISIBLE, "

+ " col8 varchar2(200) INVISIBLE, "

+ " check (col2 IS JSON), "

+ " check (col4 IS JSON), "

+ " check (col6 IS JSON), "

+ " check (col8 IS JSON))";

Util.doSQL(conn, sql);

}

private void dropTable(Connection conn) throws Exception{

String sql = " drop table tkpjb26776242_tab";

Util.trySQL(conn, sql);

}

...

2.7 Support for Implicit Results

Oracle Database supports results of SQL statements executed in a stored procedure to be

returned implicitly to the client applications without the need to explicitly use a

REF CURSOR

You can use the following methods to retrieve and process the implicit results returned by

PL/SQL procedures or blocks:

Method Description

getMoreResults

Checks if there are more results available in the result set

getMoreResults(int)

Checks if there are more results available in the result set, like

the overloaded method. This method accepts an

int

parameter

that can have one of the following values:

•

KEEP_CURRENT_RESULT

•

CLOSE_ALL_RESULTS

•

CLOSE_CURRENT_RESULT

getResultSet

Iteratively retrieves each implicit result from an executed

PL/SQL statement

Chapter 2

Support for Implicit Results

2-19

Note:

• The server-side internal driver,

kprb

does not support fetching

information about implicit results.

• Only SELECT queries can be returned implicitly.

• Applications retrieve each result set sequentially, but can fetch rows from

any result set independent of the sequence.

Suppose you have a procedure called

foo

as the following:

create procedure foo as

c1 sys_refcursor;

c2 sys_refcursor;

begin

open c1 for select * from hr.employees;

dbms_sql.return_result(c1); --return to client

-- open 1 more cursor

open c2 for select * from hr.departments;

dbms_sql.return_result (c2); --return to client

end;

The following code snippet demonstrates how to retrieve the implicit results returned

by PL/SQL procedures using the

getMoreResults

methods:

Example 1

String sql = "begin foo; end;";

...

Connection conn = DriverManager.getConnection(jdbcURL, user, password);

try {

Statement stmt = conn.createStatement ();

stmt.executeQuery (sql);

while (stmt.getMoreResults())

{

ResultSet rs = stmt.getResultSet();

System.out.println("ResultSet");

while (rs.next())

{

/* get results */

}

Suppose you have another procedure called

foo

as the following:

create or replace procedure foo asc1 sys_refcursor; c2 sys_refcursor; c3

sys_refcursor; begin open c1 for 'select * from hr.employees';

dbms_sql.return_result (c1);-- cursor 2open c2 for 'select * from

hr.departments';

dbms_sql.return_result (c2);-- cursor 3open c3 for 'select first_name from

hr.employees';

dbms_sql.return_result (c3); end;

Chapter 2

Support for Implicit Results

2-20

The following code snippet demonstrates how to retrieve the implicit results returned by

PL/SQL procedures using the

getMoreResults(int)

methods:

Example 2

String sql = "begin foo; end;";

...

Connection conn = DriverManager.getConnection(jdbcURL, user, password);

try {

Statement stmt = conn.createStatement ();

stmt.executeQuery (sql);

ResultSet rs = null;

boolean retval = stmt.getMoreResults(Statement.KEEP_CURRENT_RESULT))

if (retval)

{

rs = stmt.getResultSet();

System.out.println("ResultSet");

while (rs.next())

{

/* get results */

}

/* closes open results */

retval = stmt.getMoreResults(Statement.CLOSE_ALL_RESULTS);

if (retval)

{

System.out.println("More ResultSet available");

rs = stmt.getResultSet();

System.out.println("ResultSet");

while (rs.next())

{

/* get results */

}

/* close current result set */

retval = stmt.getMoreResults(Statement.CLOSE_CURRENT_RESULT);

if(retval)

{

System.out.println("More ResultSet available");

rs = stmt.getResultSet();

while (rs.next())

{

/* get Results */

}

2.8 Support for Lightweight Connection Validation

Starting from Oracle Database Release 18c, JDBC Thin driver supports lightweight

connection validation. Lightweight connection validation enables JDBC applications to verify

Chapter 2

Support for Lightweight Connection Validation

2-21

connection validity by sending a zero length NS data packet that does not require a

round-trip to the database.

For the releases of Oracle Database earlier than 18c, when you call the

isValid(timeout)

method to test the validity of a connection, Oracle JDBC driver

uses a ping-pong protocol, which is an expensive operation as it makes a full round-

trip to the database. Since Oracle Database Release 18c, the

isValid(timeout)

method instead sends an empty packet to the database and does not wait to receive it

back. So, connection validation is faster, which results in better application

performance.

Lightweight connection validation is disabled by default. To enable this feature, you

must set the

oracle.jdbc.defaultConnectionValidation

connection property value

SOCKET

. If this property is set, then the JDBC driver performs lightweight connection

validation, when you call the

isValid(timeout)

method.

Note:

• Lightweight connection validation checks only the underlying socket

health. When the

isValid(timeout)

method returns

true

, that is, if a

connection is termed as valid, this validation only guarantees that the

server is not unreachable (dead socket). It does not provide any status

about the server processes, like whether they are running or not.

However, by default, that is, when lightweight connection validation is not

enabled, the

isValid(timeout)

method does check whether the network

between the client and the server is intact or not.

• Only the JDBC Thin driver supports this feature.

New APIs for Lightweight Connection Validation

•

oracle.jdbc.defaultConnectionValidation

This connection property specifies the level of connection validation. The possible

values for this property are:

NONE

LOCAL

SOCKET

NETWORK

SERVER

, and

COMPLETE

These values are case-sensitive, and setting any value other than these values

throws an exception. The default value is

NETWORK

•

public boolean isValid(ConnectionValidation validation_level, int

timeout) throws SQLException

The new variation of the existing

isValid(timeout)

method accepts two

parameters: level of validation (

validation_level

) and

timeout

. The first

parameter specifies the level of connection validation.

Example 2-2 Example of Lightweight Connection Validation

The following code snippet demonstrates how to implement lightweight connection

mechanism:

...

OracleDataSource ods = new OracleDataSource();

ods.setURL(url);

ods.setUser(user);

ods.setPassword(password);

Chapter 2

Support for Lightweight Connection Validation

2-22

Connection conn = ods.getConnection();

try{

boolean isValid = ((OracleConnection)conn).

isValid(ConnectionValidation.SOCKET,timeout);

System.out.println("Connection isValid = "+isValid);

}

catch (Exception ex)

{

System.out.println("Exception :" + ex);

ex.printStackTrace();

}

... ...

2.9 Support for Deprioritization of Database Nodes

Starting from Oracle Database 12c Release 2 (12.2.0.1), JDBC drivers support

deprioritization of database nodes. When a node fails, JDBC deprioritizes it for the next 10

minutes, which is the default expiry time. For example, if there are three nodes A, B, C, and

node A is down, then connections are allocated first from nodes B and C, and then from node

A. After the default expiry time, node A is no longer deprioritized, that is, connections are

allocated from all the three nodes on availability basis. Also, during the default expiry time, if

a connection attempt to node A succeeds, then node A is no longer considered to be a

deprioritized node. You can specify the default expiry time for deprioritization using the

oracle.net.DOWN_HOSTS_TIMEOUT

system property.

For example, in the following URL,

scan_listener0

has

ip1

ip2

, and

ip3

IP addresses

configured, after retrieving its IP addresses. Now, if

ip1

is deprioritized, then the order of

trying IP addresses will be

ip2

ip3

, and then

ip1

. If all IP addresses are unavailable, then

the whole host is tried last, after trying

node_1

and

node_2

(DESCRIPTION_LIST=

(DESCRIPTION=

(ADDRESS_LIST=

(ADDRESS=(PROTOCOL=tcp)(HOST=scan_listener0)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=node_1)(PORT=1528))

(ADDRESS=(PROTOCOL=sdp)(HOST=node_2)(PORT=1527))

)

(ADDRESS_LIST=

(ADDRESS=(PROTOCOL=tcp)(HOST=node_3)(PORT=1528))

)

(CONNECT_DATA=(SERVICE_NAME=cdb3))

)

(DESCRIPTION=

(ADDRESS=(PROTOCOL=tcp)(HOST=node_0)(PORT=1528))

(CONNECT_DATA=(SERVICE_NAME=cdb3))

)

Chapter 2

Support for Deprioritization of Database Nodes

2-23

2.10 Support for Oracle Connection Manager in Traffic

Director Mode

Starting from Oracle Database Release 18c, JDBC Drivers support Oracle Connection

Manager in Traffic Director Mode, which is a proxy server that resides between the

Database clients and the Database instances.

A JDBC client connects to the Oracle Connection Manager in Traffic Director Mode,

which in turn connects to the target Oracle Database. The client sends requests in the

form of Two-Task Common (TTC) messages that Oracle Connection Manager in

Traffic Director Mode intercepts, parses, and then relays to the appropriate target

database. Once the responses arrive from the database, Oracle Connection Manager

in Traffic Director Mode transfers the responses back to the clients through TTC

messages.

The following image illustrates the architecture of Oracle Connection Manager in

Traffic Director Mode:

Figure 2-1 Architecture of Oracle Connection Manager in Traffic Director Mode

Applications and

Application Servers

Oracle Connection

Manager in Traffic

Director Mode

Oracle

Databases

See Also:

• Oracle Database Net Services Administrator's Guide for more

information about configuring the

cman.ora

file to set up Oracle

Connection Manager in Traffic Director Mode

• Oracle Database Net Services Reference for more information about

Oracle Connection Manager in Traffic Director Mode parameters

This chapter describes the following concepts:

Chapter 2

Support for Oracle Connection Manager in Traffic Director Mode

2-24

• Modes of Running Oracle Connection Manager in Traffic Director Mode

• Benefits of Oracle Connection Manager in Traffic Director Mode

2.10.1 Modes of Running Oracle Connection Manager in Traffic Director

Mode

You can run Oracle Connection Manager in Traffic Director Mode in the following connection

modes:

• Pooled connection mode

The pooled connection mode uses a new feature called Proxy Resident Connection

Pooling, which is a proxy-enabled mode of Database Resident Connection Pooling

(DRCP). The Proxy Resident Connection Pooling reduces the connection load on the

database as it multiplexes a large number of client connections over a fewer number of

database connections. Any application using Oracle Database 12c Release 1 (12.1)

JDBC drivers and later can use this connection mode.

Note:

The pooled connection mode yields best results when you use it with clients

using DRCP-aware connection pools.

• Nonpooled or dedicated connection mode

You can use the nonpooled or dedicated connection mode with applications using any

supported Oracle Database JDBC driver. However, some capabilities, such as

connection multiplexing, are not available in this mode.

Related Topics

• Overview of Database Resident Connection Pooling

See Also:

• Database Admin Guide

• Universal Connection Pool Developer's Guide

2.10.2 Benefits of Oracle Connection Manager in Traffic Director Mode

This section describes how Oracle Connection Manager in Traffic Director Mode provides

benefits to your applications.

• Transparent performance enhancements: Oracle Connection Manager in Traffic

Director Mode auto enables statement caching, row prefetching, and result set caching

during both pooled and nonpooled modes.

• Connection multiplexing: Using Proxy Resident Connection Pooling (PRCP), Oracle

Connection Manager in Traffic Director Mode (for the pooled mode) provides transparent

connection-time load balancing and run-time load balancing with the database. If you use

Chapter 2

Support for Oracle Connection Manager in Traffic Director Mode

2-25

multiple instances of Oracle Connection Manager in Traffic Director Mode, then

you can increase the scalability of your application through the implementation of

client-side connection-time load balancing or a load balancer like BIG-IP or

NGINX.

• Zero application downtime: Oracle Connection Manager in Traffic Director Mode

provides zero application downtime during planned database maintenance as well

as unplanned database outages. For Unplanned database outages, it offers zero

application downtime for read-mostly workloads. For planned database

maintanance or pluggable database (PDB) relocation, it uses different techniques

for the pooled mode and the nonpooled mode, as described in this section.

– Pooled mode:

For planned outages, Oracle Connection Manager in Traffic Director Mode

responds to the Oracle Notification Service (ONS) events. It uses database

connections from the proxy resident connection pool and redirects the

requests to the appropriate databases. When the requests complete, it drains

the connections from the pool.

For PDB relocations, Oracle Connection Manager in Traffic Director Mode

uses an in-band client notification mechanism, which works even when ONS is

not configured. This feature is available only for Oracle Database release 18c

and later.

– Nonpooled or dedicated mode

In this mode, Oracle Connection Manager in Traffic Director Mode leverages

either of the following features of Oracle Database:

* Continuous application availability to stop the service at the request

boundary

* Transparent Application Failover (TAF) to reconnect and restore simple

states

• High Availability: Oracle Connection Manager in Traffic Director Mode

implements the following techniques to avoid single point of failure, and in turn,

assures high availability:

– Multiple instances of Oracle Connection Manager in Traffic Director Mode use

a load balancer or client-side load balancing in the connection string.

– Oracle Connection Manager in Traffic Director Mode instances support rolling

upgrade.

– For planned outages, Oracle Connection Manager in Traffic Director Mode

implements graceful close of existing connections from client.

– Oracle Connection Manager in Traffic Director Mode sends in-band

notifications to Oracle Database release 18c and later clients, and ONS

notifications to all supported clients prior to Oracle Database release 18c.

• Security: Oracle Connection Manager in Traffic Director Mode provides security to

your applications in the following ways:

– It supports the Transmission Control Protocol Secure (TCPS) protocol.

– It creates a firewall based on the IP address, service name, and Secure

Socket Layer/Transport Layer Security (SSL/TLS) wallets.

– It provides protection against denial-of-service and fuzzing attacks.

Chapter 2

Support for Oracle Connection Manager in Traffic Director Mode

2-26

– It provides secure tunneling of database traffic across Oracle Database on-premises

and Oracle Cloud.

• Tenant isolation: Oracle Connection Manager in Traffic Director Mode provides tenant

isolation for increased memory and enhanced processing power.

2.11 Stored Procedure Calls in JDBC Programs

This section describes how Oracle JDBC drivers support the following kinds of stored

procedures:

• PL/SQL Stored Procedures

• Java Stored Procedures

2.11.1 PL/SQL Stored Procedures

JDBC supports the invocation of PL/SQL procedures/functions and anonymous blocks, using

either JDBC escape syntax or PL/SQL block syntax. The following PL/SQL calls would work

with any Oracle JDBC driver:

// JDBC escape syntax

CallableStatement cs1 = conn.prepareCall

( "{call proc (?,?)}" ) ; // stored proc

CallableStatement cs2 = conn.prepareCall

( "{? = call func (?,?)}" ) ; // stored func

// PL/SQL block syntax

CallableStatement cs3 = conn.prepareCall

( "begin proc (?,?); end;" ) ; // stored proc

CallableStatement cs4 = conn.prepareCall

( "begin ? := func(?,?); end;" ) ; // stored func

As an example of using the Oracle syntax, here is a PL/SQL code snippet that creates a

stored function. The PL/SQL function gets a character sequence and concatenates a suffix to

it:

create or replace function foo (val1 char)

return char as

begin

return val1 || 'suffix';

end;

The function invocation in your JDBC program should look like the following:

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:oci:@<hoststring>");

ods.setUser("HR");

ods.setPassword("hr");

Connection conn = ods.getConnection();

CallableStatement cs = conn.prepareCall ("begin ? := foo(?); end;");

cs.registerOutParameter(1,Types.CHAR);

cs.setString(2, "aa");

cs.execute();

String result = cs.getString(1);

Chapter 2

Stored Procedure Calls in JDBC Programs

2-27

2.11.2 Java Stored Procedures

You can use JDBC to call Java stored procedures through the SQL interface. The

syntax for calling Java stored procedures is the same as the syntax for calling PL/SQL

stored procedures, presuming they have been properly published. That is, you have

written call specifications to publish them to the Oracle data dictionary. Applications

can call Java stored procedures using the Native Java Interface for direct invocation of

static

Java methods.

2.12 About Processing SQL Exceptions

To handle error conditions, Oracle JDBC drivers throw SQL exceptions, producing

instances of the

java.sql.SQLException

class or its subclass. Errors can originate

either in the JDBC driver or in the database itself. Resulting messages describe the

error and identify the method that threw the error. Additional run-time information can

also be appended.

JDBC 3.0 defines only a single exception,

SQLException

. However, there are large

categories of errors and it is useful to distinguish them. Therefore, in JDBC 4.0, a set

of subclasses of the

SQLException

exception is introduced to identify the different

categories of errors.

Basic exception handling can include retrieving the error message, retrieving the error

code, retrieving the SQL state, and printing the stack trace. The

SQLException

class

includes functionality to retrieve all of this information, when available.

Retrieving Error Information

You can retrieve basic error information with the following methods of the

SQLException

class:

•

getMessage

class includes functionality to retrieve all of this information, when

available.

•

getErrorCode

class includes functionality to retrieve all of this information, when

available.

•

getSQLState

class includes functionality to retrieve all of this information, when

available.

The following example prints output from a

getMessage

method call:

catch(SQLException e)

{

System.out.println("exception: " + e.getMessage());

}

This would print the output, such as the following, for an error originating in the JDBC

driver:

exception: Invalid column type

Chapter 2

About Processing SQL Exceptions

2-28

Note:

Error message text is available in alternative languages and character sets

supported by Oracle.

Printing the Stack Trace

The

SQLException

class provides the

printStackTrace()

method for printing a stack trace.

This method prints the stack trace of the

Throwable

object to the standard error stream. You

can also specify a

java.io.PrintStream

object or

java.io.PrintWriter

object for output.

The following code fragment illustrates how you can catch SQL exceptions and print the

stack trace.

try { <some code> }

catch(SQLException e) { e.printStackTrace (); }

To illustrate how the JDBC drivers handle errors, assume the following code uses an

incorrect column index:

// Iterate through the result and print the employee names

// of the code

try {

while (rset.next ())

System.out.println (rset.getString (5)); // incorrect column index

}

catch(SQLException e) { e.printStackTrace (); }

Assuming the column index is incorrect, running the program would produce the following

error text:

java.sql.SQLException: Invalid column index

at oracle.jdbc.OracleDriver.OracleResultSetImpl.getDate(OracleResultSetImpl.java:1556)

at Employee.main(Employee.java:41)

Related Topics

• JDBC Error Messages

• Oracle Database Error Messages Reference

Chapter 2

About Processing SQL Exceptions

2-29

Part II

Oracle JDBC

This part includes chapters that discuss the different Java Database Connectivity (JDBC)

versions that Oracle Database 21c supports. It also includes chapters that cover features

specific to JDBC Thin driver, JDBC Oracle Call Interface (OCI) driver, and the server-side

internal driver.

Part II contains the following chapters:

• JDBC Standards Support

• Oracle Extensions

• Features Specific to JDBC Thin

• Features Specific to JDBC OCI Driver

• Server-Side Internal Driver

JDBC Standards Support

Oracle Java Database Connectivity (JDBC) drivers support different versions of the JDBC

standard features. These features are provided through the

oracle.jdbc

and

oracle.sql

packages. These packages support Java Development Kit (JDK) release 8 and Java

Development Kit (JDK) release 11.

This chapter discusses the JDBC standards support in Oracle JDBC drivers for the most

recent releases. It contains the following sections:

• Support for JDBC 4.2 Standard

• Support for JDBC 4.3 Standard

3.1 Support for JDBC 4.2 Standard

Oracle Database Release 21c JDBC drivers provide support for JDBC 4.2 standard through

JDK 8. This section lists some of the important methods added in this release.

The %Large% Methods

This release of Oracle JDBC drivers support the following methods introduced in JDBC 4.2

standard, which deal with

long

values:

•

executeLargeBatch()

•

executeLargeUpdate(String sql)

•

executeLargeUpdate(String sql, int autoGeneratedKeys)

•

executeLargeUpdate(String sql, int[] columnIndexes)

•

executeLargeUpdate(String sql, String[] columnNames)

•

getLargeMaxRows()

•

getLargeUpdateCount()

•

setLargeMaxRows(long max)

These new methods are available as part of the

java.sql.Statement

interface. The

%Large%

methods are identical to the corresponding non-large methods, except that they work with

long

values instead of

int

values. For example, the

executeUpdate

method returns the

number of rows updated as an

int

value, whereas, the

executeLargeUpdate

method returns

the number of rows updated as a

long

value. If the number of rows is greater than the value

Integer.MAX_VALUE

, then your application must use the

executeLargeUpdate

method.

The following code snippet shows how to use the

executeLargeUpdate(String sql)

method:

...

Statement stmt = conn.createStatement();

stmt.executeQuery("create table BloggersData (FIRST_NAME varchar(100), ID

int)");

long updateCount = stmt.executeLargeUpdate("insert into BloggersData

3-1

(FIRST_NAME,ID) values('John',1)");

...

The SQLType Methods

This release of Oracle JDBC drivers support the following methods introduced in

JDBC 4.2 standard, which take

SQLType

parameters:

•

setObject

The

setObject

method sets the value of the designated parameter for the

specified object. This method is similar to the

setObject(int parameterIndex,

Object x, SQLType targetSqlType, int scaleOrLength)

method, except that it

assumes a scale of zero. The default implementation of this method throws

SQLFeatureNotSupportedException

void setObject(int parameterIndex, java.lang.Object x, SQLType

targetSqlType) throws SQLException

•

updateObject

The

updateObject

method takes the column index as a parameter and updates

the designated column with an Object value.

•

registerOutParameter

The

registerOutParameter

method registers a specified parameter to be of JDBC

type

SQLType

The following code snippet shows how to use the

setObject

method:

...

int empId = 100;

connection.prepareStatement("SELECT FIRST_NAME, LAST_NAME FROM

EMPLOYEES WHERE EMPNO = ?");

preparedStatement.setObject(1, Integer.valueOf(empId),

OracleType.NUMBER);

...

See Also:

JDBC 4.2 Documentation

3.2 Support for JDBC 4.3 Standard

Starting from Release 19c, Oracle Database JDBC drivers provide support for

Standard JDBC 4.3 features through JDK 10 and later versions. This section describes

some of the important methods added in this release.

Sharding Support

Sharding is a data tier architecture, where data is horizontally partitioned across

independent databases. Each database in such a configuration is called a shard. All

Chapter 3

Support for JDBC 4.3 Standard

3-2

shards together make up a single logical database, which is referred to as a sharded

database (SDB). You can use the

DatabaseMetaData.supportsSharding

method to

determine whether a JDBC Driver supports sharding or not.

Sharding support includes addition of the following APIs:

•

javax.sql.XAConnectionBuilder

Interface

This is a builder interface created from a

XADataSource

object, which you can use to

establish a connection to the database that the data source object represents.

•

java.sql.ShardingKey

Interface

This interface is used to indicate that the current object represents a Sharding Key. You

can create a

ShardingKey

instance using the

ShardingKeyBuilder

interface.

•

java.sql.ShardingKeyBuilder

Interface

This is a builder interface created from a

DataSource

XADataSource

object, used to

create a

ShardingKey

with subkeys of supported data types.

See Also:

Overview of Database Sharding for JDBC Users

Enhancements to the java.sql.Connection Interface

The following methods have been added to the

java.sql.Connection

Interface:

•

default void beginRequest throws SQLException

•

default void endRequest throws SQLException

•

default void setShardingKey(ShardingKey shardingKey) throws SQLException

•

default void setShardingKey(ShardingKey shardingKey, ShardingKey

superShardingKey) throws SQLException

•

default void setShardingKeyIfValid(ShardingKey shardingKey, int timeout)

throws SQLException

•

default void setShardingKeyIfValid(ShardingKey shardingKey, ShardingKey

superShardingKey, int timeout) throws SQLException

Enhancements to the java.sql.DatabaseMetaData Interface

The following methods have been added to the

java.sql.DatabaseMetaData

Interface:

default boolean supportsSharding() throws SQLException

Enhancements to the java.sql.Statement Interface

The following methods have been added to the

java.sql.Statement

Interface:

•

default String enquoteIdentifier(String identifier, Boolean alwaysQuote)

throws SQLException

•

default String enquoteLiteral(String val) throws SQLException

•

default String enquoteNCharLiteral(String val) throws SQLException

Chapter 3

Support for JDBC 4.3 Standard

3-3

•

default boolean isSimpleIdentifier(String identifier) throws

SQLException

See Also:

Oracle Database JDBC Java API Reference

Chapter 3

Support for JDBC 4.3 Standard

3-4

Oracle Extensions

Oracle provides Java classes and interfaces that extend the Java Database Connectivity

(JDBC) standard implementation, enabling you to access and manipulate Oracle data types

and use Oracle performance extensions. This chapter provides an overview of the classes

and interfaces provided by Oracle that extend the JDBC standard implementation. It also

describes some of the key support features of the extensions.

This chapter contains the following sections:

• Overview of Oracle Extensions

• Features of the Oracle Extensions

• Oracle JDBC Packages

• Oracle Character Data Types Support

• Additional Oracle Type Extensions

• DML Returning

• Accessing PL/SQL Associative Arrays

Related Topics

• Performance Extensions

4.1 Overview of Oracle Extensions

Beyond standard features, Oracle JDBC drivers provide Oracle-specific type extensions and

performance extensions. These extensions are provided through the following Java

packages:

•

oracle.sql

Provides classes that represent SQL data in Oracle format

•

oracle.jdbc

Provides interfaces to support database access and updates in Oracle type formats

Related Topics

• Oracle JDBC Packages

4.2 Features of the Oracle Extensions

The Oracle extensions to JDBC include a number of features that enhance your ability to

work with Oracle Databases. These include the following:

• Database Management Using JDBC

• Support for Oracle Data Types

• Support for Oracle Objects

4-1

• Support for Schema Naming

• DML Returning

• About Accessing PL/SQL Associative Arrays

4.2.1 Database Management Using JDBC

Starting from Oracle Database 11g Release 1, the

oracle.jdbc.OracleConnection

interface has two JDBC methods,

startup

and

shutdown

, which enable you to start up

and shut down an Oracle Database instance.

Note:

My Oracle Support Note 335754.1 announces the desupport of the

oracle.jdbc.driver.*

package in Oracle Database 11g JDBC drivers. In

other words, Oracle Database 10g Release 2 was the last database to

support this package and any API depending on the

oracle.jdbc.driver.*

package will fail to compile in the current release of the Database. You must

remove such APIs and migrate to the standard APIs. For example, if your

code uses the

oracle.jdbc.CustomDatum

and

oracle.jdbc.CustomDatumFactory

interfaces, then you must replace them

with the

java.sql.Struct

java.sql.SQLData

interfaces.

Related Topics

• Database Administration

4.2.2 Support for Oracle Data Types

One of the features of the Oracle JDBC extensions is the type support in the

oracle.sql

package. This package includes classes that are an exact representation

of the data in Oracle format. Keep the following important points in mind, when you

use

oracle.sql

types in your program:

• For numeric type of data, the conversion to standard Java types does not

guarantee to retain full precision due to limitations of the data conversion process.

Use the

BigDecimal

type to minimize any data loss issues.

• For certain data types, the conversion to standard Java types can be dependent

on the system settings and your program may not run as expected. This is a

known limitation while converting data from

oracle.sql

types to standard Java

types.

• If the functionalities of your program is limited to reading data from one table and

writing the same to another table, then for numeric and date data,

oracle.sql

types are slightly faster as compared to standard Java types. But, if your program

involves even a simple data manipulation operation like compare or print, then

standard Java types are faster.

•

oracle.sql.CHAR

is not an exact representation of the data in Oracle format.

oracle.sql.CHAR

is constructed from

java.lang.String

. There is no advantage

of using

oracle.sql.CHAR

because

java.lang.String

is always faster and

Chapter 4

Features of the Oracle Extensions

4-2

represents the same character sets, excluding a couple of desupported character sets.

Note:

Oracle strongly recommends you to use standard Java types and convert any

existing

oracle.sql

type of data to standard Java types. Internally, the Oracle

JDBC drivers strive to maximize the performance of Java standard types.

oracle.sql

types are supported only for backward compatibility and their use is

discouraged.

Related Topics

• Package oracle.sql

The

oracle.sql

package supports direct access to data in SQL format. This package

consists primarily of classes that provide Java mappings to SQL data types and their

support classes. Essentially, the classes act as Java containers for SQL data.

• Oracle Character Data Types Support

• Additional Oracle Type Extensions

4.2.3 Support for Oracle Objects

Oracle JDBC supports the use of structured objects in the database, where an object data

type is a user-defined type with nested attributes. For example, a user application could

define an

Employee

object type, where each

Employee

object has a

firstname

attribute

(character string), a

lastname

attribute (character string), and an

employeenumber

attribute

(integer).

Oracle JDBC supports Oracle object data types. When you work with Oracle object data

types in a Java application, you must consider the following:

• How to map between Oracle object data types and Java classes

• How to store Oracle object attributes in corresponding Java objects

• How to convert attribute data between SQL and Java formats

• How to access data

Oracle objects can be mapped either to the weak

java.sql.Struct

type or to strongly typed

customized classes. These strong types are referred to as custom Java classes, which must

implement either the standard

java.sql.SQLData

interface or the Oracle extension

oracle.jdbc.OracleData

interface. Each interface specifies methods to convert data

between SQL and Java.

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

OracleData

interface has

replaced the

ORAData

interface.

Oracle recommends the use of the Oracle JVM Web Service Call-Out Utility to create custom

Java classes to correspond to your Oracle objects.

Chapter 4

Features of the Oracle Extensions

4-3

Related Topics

• Working with Oracle Object Types

• Oracle Database Java Developer’s Guide

4.2.4 Support for Schema Naming

Oracle object data type classes have the ability to accept and return fully qualified

schema names. A fully qualified schema name has this syntax:

{[schema_name].}[sql_type_name]

Where,

schema_name

is the name of the schema and

sql_type_name

is the SQL type

name of the object.

schema_name

and

sql_type_name

are separated by a period (

To specify an object type in JDBC, use its fully qualified name. It is not necessary to

enter a schema name if the type name is in the current naming space, that is, the

current schema. Schema naming follows these rules:

• Both the schema name and the type name may or may not be within quotation

marks. However, if the SQL type name has a period in it, such as

CORPORATE.EMPLOYEE

, the type name must be quoted.

• The JDBC driver looks for the first period in the object name that is not within

quotation marks and uses the string before the period as the schema name and

the string following the period as the type name. If no period is found, then the

JDBC driver takes the current schema as default. That is, you can specify only the

type name, without indicating a schema, instead of specifying the fully qualified

name if the object type name belongs to the current schema. This also explains

why you must put the type name within quotation marks if the type name has a dot

in it.

For example, assume that user

creates a type called

person.address

and then

wants to use it in his session.

may want to skip the schema name and pass in

person.address

to the JDBC driver. In this case, if

person.address

is not within

quotation marks, then the period is detected and the JDBC driver mistakenly

interprets

person

as the schema name and

address

as the type name.

• JDBC passes the object type name string to the database unchanged. That is, the

JDBC driver does not change the character case even if the object type name is

within quotation marks.

For example, if

HR.PersonType

is passed to the JDBC driver as an object type

name, then the JDBC driver passes the string to the database unchanged. As

another example, if there is white space between characters in the type name

string, then the JDBC driver will not remove the white space.

4.2.5 DML Returning

Oracle Database supports the use of the

RETURNING

clause with data manipulation

language (DML) statements. This enables you to combine two SQL statements into

one. Both the Oracle JDBC Oracle Call Interface (OCI) driver and the Oracle JDBC

Thin driver support DML returning.

Chapter 4

Features of the Oracle Extensions

4-4

See Also:

"DML Returning"

4.2.6 PL/SQL Associative Arrays

Oracle JDBC drivers enable JDBC applications to make PL/SQL calls with Associative Array

parameters. Oracle JDBC drivers support PL/SQL Associative Arrays of scalar data types

See Also:

"Accessing PL/SQL Associative Arrays"

4.3 Oracle JDBC Packages

This section describes the following Java packages, which support the Oracle JDBC

extensions:

• Package oracle.sql

• Package oracle.sql.json

• Package oracle.jdbc

4.3.1 Package oracle.sql

The

oracle.sql

package supports direct access to data in SQL format. This package

consists primarily of classes that provide Java mappings to SQL data types and their support

classes. Essentially, the classes act as Java containers for SQL data.

Each of the

oracle.sql.*

data type classes extends

oracle.sql.Datum

, a superclass that

encapsulates functionality common to all the data types. Some of the classes are for JDBC

2.0-compliant data types. These classes, implement standard JDBC 2.0 interfaces in the

java.sql

package, as well as extending the

oracle.sql.Datum

class.

The

LONG

and

LONG

RAW

SQL types and

REF

CURSOR

type category have no

oracle.sql.*

classes. Use standard JDBC functionality for these types. For example, retrieve

LONG

RAW

data as input streams using the standard JDBC result set and callable statement

methods

getBinaryStream

and

getCharacterStream

. Use the

getCursor

method for

REF

CURSOR

types.

Note:

Oracle recommends the use of standard JDBC types or Java types whenever

possible. The types in the package

oracle.sql.*

are provided primarily for

backward compatibility or for support of a few Oracle specific features such as

OPAQUE

OracleData

TIMESTAMPTZ

, and so on.

Chapter 4

Oracle JDBC Packages

4-5

General oracle.sql.* Data Type Support

Each of the Oracle data type classes provides, among other things, the following:

• Data storage as Java byte arrays for SQL data

• A

getBytes()

method, which returns the SQL data as a byte array

• A

toJdbc()

method that converts the data into an object of a corresponding Java

class as defined in the JDBC specification

The JDBC driver does not convert Oracle-specific data types that are not part of

the JDBC specification, such as

BFILE

. The driver returns the object in the

corresponding

oracle.sql.*

format.

• Appropriate

xxxValue

methods to convert SQL data to Java type. For example,

stringValue

intValue

booleanValue

dateValue

, and

bigDecimalValue

• Additional conversion methods,

getXXX

and

setXXX

, as appropriate, for the

functionality of the data type, such as methods in the large object (LOB) classes

that get the data as a stream and methods in the

REF

class that get and set object

data through the object reference.

Overview of Class oracle.sql.STRUCT

oracle.sql.STRUCT

class is the Oracle implementation of

java.sql.Struct

interface.

This class is a value class and you should not change the contents of the class after

construction. This class, as with all

oracle.sql.*

data type classes, is a subclass of

the

oracle.sql.Datum

class.

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.STRUCT

class is deprecated and replaced with the

oracle.jdbc.OracleStruct

interface, which is a part of the

oracle.jdbc

package. Oracle strongly

recommends you to use the methods available in the

java.sql

package,

where possible, for standard compatibility and methods available in the

oracle.jdbc

package for Oracle specific extensions. Refer to MoS Note

1364193.1 for more information about the

oracle.jdbc.OracleStruct

interface.

Overview of Class oracle.sql.REF

The

oracle.sql.REF

class is the generic class that supports Oracle object references.

This class, as with all

oracle.sql.*

data type classes, is a subclass of the

oracle.sql.Datum

class.

Chapter 4

Oracle JDBC Packages

4-6

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.REF

class is

deprecated and replaced with the

oracle.jdbc.OracleRef

interface, which is a part

of the

oracle.jdbc

package. Oracle strongly recommends you to use the methods

available in the

java.sql

package, where possible, for standard compatibility and

methods available in the

oracle.jdbc

package for Oracle specific extensions. Refer

to MoS Note 1364193.1 for more information about the

oracle.jdbc.OracleRef

interface.

The

REF

class has methods to retrieve and pass object references. However, selecting an

object reference retrieves only a pointer to an object. This does not materialize the object

itself. But the

REF

class also includes methods to retrieve and pass the object data. You

cannot create

REF

objects in your JDBC application. You can only retrieve existing

REF

objects

from the database.

You should use the JDBC standard type,

java.sql.Ref

, and the JDBC standard methods in

preference to using

oracle.sql.REF

. If you want your code to be more portable, then you

must use the standard type because only the Oracle JDBC drivers will use instances of

oracle.sql.REF

type.

Overview of Classes oracle.sql.BLOB, oracle.sql.CLOB, oracle.sql.BFILE

Binary large objects (BLOBs), character large objects (CLOBs), and binary files (BFILEs) are

for data items that are too large to store directly in a database table. Instead, the database

table stores a locator that points to the location of the actual data.

Note:

• Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.BLOB

and

Oracle.sql.CLOB

classes are deprecated and replaced with the

oracle.jdbc.OracleBlob

and

oracle.jdbc.OracleClob

interfaces respectively,

which are a part of the

oracle.jdbc

package. Oracle strongly recommends you

to use the methods available in the

java.sql

package, where possible, for

standard compatibility and methods available in the

oracle.jdbc

package for

Oracle specific extensions. Refer to MoS Note 1364193.1 for more information

about the

oracle.jdbc.OracleBlob

and

oracle.jdbc.OracleClob

interfaces.

•

oracle.sql.BFILE

is an Oracle proprietary extension and there is no JDBC

standard equivalent.

The

oracle.sql

package supports these data types in several ways:

• BLOBs point to large unstructured binary data items and are supported by the

oracle.sql.BLOB

class.

• CLOBs point to large character data items and are supported by the

oracle.sql.CLOB

class.

• BFILEs point to the content of external files (operating system files) and are supported by

the

oracle.sql.BFILE

class. BFiles are read-only.

Chapter 4

Oracle JDBC Packages

4-7

You can select a BLOB, CLOB, or BFILE locator from the database using a standard

SELECT

statement. However, you receive only the locator, and not the data. Additional

steps are necessary to retrieve the data.

Overview of Classes oracle.sql.DATE, oracle.sql.NUMBER, and oracle.sql.RAW

These classes hold primitive SQL data types in Oracle native representation. In most

cases, these types are not used internally by the drivers and you should use the

standard JDBC types instead.

Java

Double

and

Float

NaN

values do not have an equivalent Oracle

NUMBER

representation. For example, for Oracle

BINARY_FLOAT

and

BINARY_DOUBLE

data types,

negative zero is coerced to positive zero and all NaNs are coerced to the canonical

one. So, a

NullPointerException

is thrown whenever a

Double.NaN

value or a

Float.NaN

value is converted into an Oracle

NUMBER

using the

oracle.sql.NUMBER

class. For instance, the following code throws a

NullPointerException

oracle.sql.NUMBER n = new oracle.sql.NUMBER(Double.NaN);

System.out.println(n.doubleValue()); // throws NullPointerException

Overview of Classes oracle.sql.TIMESTAMP, oracle.sql.TIMESTAMPTZ, and

oracle.sql.TIMESTAMPLTZ

The JDBC drivers support the following date/time data types:

•

TIMESTAMP

(

TIMESTAMP

)

•

TIMESTAMP WITH TIME ZONE

(

TIMESTAMPTZ

)

•

TIMESTAMP WITH LOCAL TIME ZONE

(

TIMESTAMPLTZ

)

The JDBC drivers allow conversions between

DATE

and date/time data types. For

example, you can access a

TIMESTAMP WITH TIME ZONE

column as a

DATE

value.

The JDBC drivers support the most popular time zone names used in the industry as

well as most of the time zone names defined in the JDK. Time zones are specified by

using the

java.util.TimeZone

class.

Note:

• Do not use

TimeZone.getTimeZone

to create time zone objects. The

Oracle time zone data types support more time zone names than JDK.

• If a result set contains a

TIMESTAMPLTZ

column followed by a

LONG

column, then reading the

LONG

column results in an error.

The following code shows how the

TimeZone

and

Calendar

objects are created for

US_PACIFIC

, which is a time zone name not defined in JDK:

TimeZone tz = TimeZone.getDefault();

tz.setID("US_PACIFIC");

GregorianCalendar gcal = new GregorianCalendar(tz);

The following Java classes represent the SQL date/time types:

•

oracle.sql.TIMESTAMP

Chapter 4

Oracle JDBC Packages

4-8

•

oracle.sql.TIMESTAMPTZ

•

oracle.sql.TIMESTAMPLTZ

Before accessing

TIMESTAMP WITH LOCAL TIME ZONE

data, call the

OracleConnection.setSessionTimeZone(String regionName)

method to set the session

time zone. When this method is called, the JDBC driver sets the session time zone of the

connection and saves the session time zone so that any

TIMESTAMP WITH LOCAL TIME ZONE

data accessed through JDBC can be adjusted using the session time zone.

Note:

TIMESTAMP WITH TIME ZONE

and

TIMESTAMP WITH LOCAL TIME ZONE

types can be

represented as standard

java.sql.Timestamp

type. The byte representation of

TIMESTAMP WITH TIME ZONE

and

TIMESTAMP WITH LOCAL TIME ZONE

types to

java.sql.Timestamp

is straight forward. This is because the internal format of

TIMESTAMP WITH TIME ZONE

and

TIMESTAMP WITH LOCAL TIME ZONE

data types is

GMT, and

java.sql.Timestamp

type objects internally use a milliseconds time value

that is the number of milliseconds since EPOCH. However, the

String

representation of these data types requires time zone information that is obtained

dynamically from the server and cached on the client side.

In earlier versions of JDBC drivers, the cache of time zone was shared across

different connections. This used to cause problems sometimes due to

incompatibility in various time zones. Starting from Oracle Database 11 Release 2

version of JDBC drivers, the time zone cache is based on the time zone version

supplied by the database. This newly designed cache avoids any issues related to

version incompatibility of time zones.

Overview of Class oracle.sql.OPAQUE

The

oracle.sql.OPAQUE

class provides the name and characteristics of the

OPAQUE

type and

any attributes. The

OPAQUE

type provides access only to the uninterrupted bytes of the

instance.

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.OPAQUE

class

is deprecated and replaced with the

oracle.jdbc.OracleOpaque

interface, which is

a part of the

oracle.jdbc

package. Oracle recommends you to use the methods

available in the

java.sql

package, where possible, for standard compatibility and

methods available in the

oracle.jdbc

package for Oracle specific extensions. Refer

to MoS Note 1364193.1 for more information about the

oracle.jdbc.OracleOpaque

interface.

Related Topics

• Oracle Database SQL Language Reference

• JDBC Java API Reference

Chapter 4

Oracle JDBC Packages

4-9

• Working with Large Objects and SecureFiles

Large Objects (LOBs) are a set of data types that are designed to hold large

amounts of data. This chapter describes how to use Java Database Connectivity

(JDBC) to access and manipulate LOBs and SecureFiles using either the data

interface or the locator interface.

4.3.2 Package oracle.sql.json

Starting with release 21c, Oracle Database provides a native JSON SQL type in the

database. The

oracle.sql.json

package provides functionality to work with the JSON

type values.

Specifically, you can use the

oracle.sql.json

package to perform the following tasks:

• Store and retrieve JSON type values in the database

• Read, create, and modify JSON type values

• Encode or decode JSON type values in the same binary JSON storage format as

used by the database

• Convert JSON type values to and from JSON text

• Bind and access JSON type values using the JSON-P interfaces like

javax.json.*

See Also:

JDBC Java API Reference

The following example shows how to insert, get, and modify JSON type values:

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import oracle.jdbc.OracleConnection;

import oracle.jdbc.pool.OracleDataSource;

import oracle.sql.json.OracleJsonFactory;

import oracle.sql.json.OracleJsonObject;

public class JsonExample {

public static void main(String[] args) throws SQLException {

OracleDataSource ds = new OracleDataSource();

ds.setURL("jdbc:oracle:thin:@myhost:1521:orcl");

ds.setUser(<user>);

ds.setPassword(<password>);

OracleConnection con = (OracleConnection) ds.getConnection();

// create a table with a JSON column and insert one value

Statement stmt = con.createStatement();

stmt.executeUpdate("CREATE TABLE fruit (data JSON)");

stmt.executeUpdate("INSERT INTO fruit VALUES

Chapter 4

Oracle JDBC Packages

4-10

('{"name":"pear","count":10}')");

// create another JSON object

OracleJsonFactory factory = new OracleJsonFactory();

OracleJsonObject orange = factory.createObject();

orange.put("name", "orange");

orange.put("count", 12);

// insert the orange object

PreparedStatement pstmt = con.prepareStatement("INSERT INTO fruit VALUES

(:1)");

pstmt.setObject(1, orange, OracleType.JSON);

pstmt.executeUpdate();

pstmt.close();

// retrieve the pear object

ResultSet rs = stmt.executeQuery("SELECT data FROM fruit f WHERE

f.data.name = 'pear'");

rs.next();

OracleJsonObject pear = rs.getObject(1, OracleJsonObject.class);

int count = pear.getInt("count");

// create a modifiable copy of the pear object

pear = factory.createObject(pear);

pear.put("count", count + 1);

pear.put("color", "green");

// update the pear object

pstmt = con.prepareStatement("UPDATE fruit f SET data = :1 WHERE

f.data.name = 'pear');

pstmt.setObject(1, pear, OracleType.JSON);

pstmt.executeUpdate();

pstmt.close();

rs.close();

stmt.close();

con.close();

}

Compatibility with Client Libraries Prior to Release 21c

If you do not upgrade the earlier versions of your client library to 21c, then your application

treats the JSON type column in the database as a String, BLOB, or CLOB column. So, to

query the JSON type column, you must use the query methods for those data types.

However, when you use the BLOB APIs like the

getBlob

method, they return an error, even

after you upgrade the client library. So, Oracle recommends that for BLOB data type, you use

the

getBytes

method or the

getBinaryStream

method, which will return text data with UTF-8

JSON encoding. The following code snippets show how to query a JSON type column for

BLOB data type:

Example: Using the

getBinaryStream

Method

public static void fetchStream(ResultSet rs) throws SQLException, IOException

Chapter 4

Oracle JDBC Packages

4-11

{

InputStream is = rs.getBinaryStream("JCOL");

ByteArrayOutputStream baos = new ByteArrayOutputStream();

int n = -1;

byte[] buffer = new byte[1024];

while ((n = is.read(buffer)) != -1) {

baos.write(buffer, 0, n);

}

is.close();

byte[] bytes = baos.toByteArray();

System.out.println(new String(bytes, StandardCharsets.UTF_8));

}

public static void example1(Connection con) throws SQLException,

IOException

{

Statement stmt = con.createStatement();

ResultSet rs = stmt.executeQuery("select jcol from jtab where rownum

< 2");

while (rs.next()){

fetchStream(rs);

}

Example: Using the

getBytes

Method

public static void fetchString(ResultSet rs) throws SQLException

{

byte[] utf8 = rs.getBytes("JCOL");

System.out.println(new String(utf8, StandardCharsets.UTF_8));

}

public static void example2(Connection con) throws SQLException

{

Statement stmt = con.createStatement();

ResultSet rs = stmt.executeQuery("select jcol from jtab where rownum

< 2");

while (rs.next()){

fetchString(rs);

}

4.3.3 Package oracle.jdbc

The interfaces of the

oracle.jdbc

package define the Oracle extensions to the

interfaces in

java.sql

. These extensions provide access to Oracle SQL-format data

and other Oracle-specific functionality, including Oracle performance enhancements.

Chapter 4

Oracle JDBC Packages

4-12

See Also:

"The oracle.jdbc Package"

4.4 Oracle Character Data Types Support

Oracle character data types include the SQL CHAR and NCHAR data types. The following

sections describe how these data types can be accessed using the

oracle.sql.*

classes:

• SQL CHAR Data Types

• SQL NCHAR Data Types

• Class oracle.sql.CHAR

4.4.1 SQL CHAR Data Types

The SQL CHAR data types include

CHAR

VARCHAR2

, and

CLOB

. These data types let you store

character data in the database character set encoding scheme. The character set of the

database is established when you create the database.

4.4.2 SQL NCHAR Data Types

The SQL

NCHAR

data types were created for Globalization Support. The SQL

NCHAR

data

types include

NCHAR

NVARCHAR2

, and

NCLOB

. These data types enable you to store Unicode

data in the database

NCHAR

character set encoding. The

NCHAR

character set, which never

changes, is established when you create the database.

Note:

Because the

UnicodeStream

class is deprecated in favor of the

CharacterStream

class, the

setUnicodeStream

and

getUnicodeStream

methods are not supported for

NCHAR

data type access. Use the

setCharacterStream

method and the

getCharacterStream

method if you want to use stream access.

The usage of SQL

NCHAR

data types is similar to that of the SQL

CHAR

data types. JDBC uses

the same classes and methods to access SQL

NCHAR

data types that are used for the

corresponding SQL

CHAR

data types. Therefore, there are no separate, corresponding classes

defined in the

oracle.sql

package for SQL

NCHAR

data types. Similarly, there is no separate,

corresponding constant defined in the

oracle.jdbc.OracleTypes

class for SQL

NCHAR

data

types.

See Also:

"NCHAR_ NVARCHAR2_ NCLOB and the defaultNChar Property"

Chapter 4

Oracle Character Data Types Support

4-13

Note:

The

setFormOfUse

method must be called before the

registerOutParameter

method is called in order to avoid unpredictable results.

The following code shows how to access SQL

NCHAR

data:

// Table TEST has the following columns:

// - NUMBER

// - NVARCHAR2

// - NCHAR

oracle.jdbc.OraclePreparedStatement pstmt =

(oracle.jdbc.OraclePreparedStatement)

conn.prepareStatement("insert into TEST values(?, ?, ?)");

// oracle.jdbc.OraclePreparedStatement.FORM_NCHAR should be used for all NCHAR,

// NVARCHAR2 and NCLOB data types.

pstmt.setInt(1, 1); // NUMBER column

pstmt.setNString(2, myUnicodeString1); // NVARCHAR2 column

pstmt.setNString(3, myUnicodeString2); // NCHAR column

pstmt.execute();

4.4.3 Class oracle.sql.CHAR

The

oracle.sql.CHAR

class is used by Oracle JDBC in handling and converting

character data. This class provides the Globalization Support functionality to convert

character data. This class has two key attributes: Globalization Support character set

and the character data. The Globalization Support character set defines the encoding

of the character data. It is a parameter that is always passed when a

CHAR

object is

constructed. Without the Globalization Support character set information, the data

bytes in the

CHAR

object are meaningless. The

oracle.sql.CHAR

class is used for both

SQL

CHAR

and SQL

NCHAR

data types.

Note:

In versions of Oracle JDBC drivers prior to 10g Release 1, there were

performance advantages to using the

oracle.SQL.CHAR

. Starting from Oracle

Database 10g, there are no longer any such advantages. In fact, optimum

performance is achieved using the

java.lang.String

. All Oracle JDBC

drivers handle all character data in the Java UCS2 character set. Using the

oracle.sql.CHAR

does not prevent conversions between the database

character set and UCS2 character set.

The only remaining use of the

oracle.sql.CHAR

class is to handle character data in

the form of raw bytes encoded in an Oracle Globalization Support character set. All

character data retrieved from Oracle Database should be accessed using the

Chapter 4

Oracle Character Data Types Support

4-14

java.lang.String

class. When processing byte data from another source, you can use an

oracle.sql.CHAR

to convert the bytes to

java.lang.String

To convert an

oracle.sql.CHAR

, you must provide the data bytes and an

oracle.sql.CharacterSet

instance that represents the Globalization Support character set

used to encode the data bytes.

The

CHAR

objects that are Oracle object attributes are returned in the database character set.

JDBC application code rarely needs to construct

CHAR

objects directly, because the JDBC

driver automatically creates

CHAR

objects, when it is needed to create them on those rare

occasions.

To construct a

CHAR

object, you must provide character set information to the

CHAR

object by

way of an instance of the

CharacterSet

class. Each instance of this class represents one of

the Globalization Support character sets that Oracle supports. A

CharacterSet

instance

encapsulates methods and attributes of the character set, mainly involving functionality to

convert to or from other character sets.

Constructing an oracle.sql.CHAR Object

Follow these general steps to construct a

CHAR

object:

1. Create a

CharacterSet

object by calling the

static

CharacterSet.make

method.

This method is a factory for the character set instance. The

make

method takes an integer

as input, which corresponds to a character set ID that Oracle supports. For example:

int oracleId = CharacterSet.JA16SJIS_CHARSET; // this is character set ID,

// 832

...

CharacterSet mycharset = CharacterSet.make(oracleId);

Each character set that Oracle supports has a unique, predefined Oracle ID.

2. Construct a

CHAR

object.

Pass a string, or the bytes that represent the string, to the constructor along with the

CharacterSet

object that indicates how to interpret the bytes based on the character set.

For example:

String mystring = "teststring";

...

CHAR mychar = new CHAR(teststring, mycharset);

There are multiple constructors for

CHAR

, which can take a

String

, a

byte

array, or an

object as input along with the

CharacterSet

object. In the case of a

String

, the string is

converted to the character set indicated by the

CharacterSet

object before being placed

into the

CHAR

object.

Chapter 4

Oracle Character Data Types Support

4-15

Note:

• The

CharacterSet

object cannot be a null value.

• The

CharacterSet

class is an abstract class, therefore it has no

constructor. The only way to create instances is to use the

make

method.

• The server recognizes the special value

CharacterSet.DEFAULT_CHARSET

as the database character set. For

the client, this value is not meaningful.

• Oracle does not intend or recommend that users extend the

CharacterSet

class.

oracle.sql.CHAR Conversion Methods

The

CHAR

class provides the following methods for translating character data to strings:

•

getString

This method converts the sequence of characters represented by the

CHAR

object

to a string, returning a Java

String

object. If you enter an invalid

OracleID

, then

the character set will not be recognized and the

getString

method will throw a

SQLException

exception.

•

toString

This method is identical to the

getString

method. But if you enter an invalid

OracleID

, then the character set will not be recognized and the

toString

method

will return a hexadecimal representation of the

CHAR

data and will not throw a

SQLException

exception.

•

getStringWithReplacement

This method is identical to the

getString

method, except a default replacement

character replaces characters that have no unicode representation in the

CHAR

object character set. This default character varies from character set to character

set, but is often a question mark (

The database server and the client, or application running on the client, can use

different character sets. When you use the methods of the

CHAR

class to transfer data

between the server and the client, the JDBC drivers must convert the data from the

server character set to the client character set or vice versa. To convert the data, the

drivers use Globalization Support.

See Also:

Globalization Support

Chapter 4

Oracle Character Data Types Support

4-16

4.5 Additional Oracle Type Extensions

Oracle JDBC drivers support the Oracle-specific

BFILE

and

ROWID

data types and

REF

CURSOR

types, which are not part of the standard JDBC specification. This section describes the

ROWID

and

REF CURSOR

type extensions. The

ROWID

is supported as a Java string, and

REF

CURSOR

types are supported as JDBC result sets.

This section covers the following topics:

• Oracle ROWID Type

• Oracle REF CURSOR Type Category

• Oracle BINARY_FLOAT and BINARY_DOUBLE Types

• Oracle SYS.ANYTYPE and SYS.ANYDATA Types

• The oracle.jdbc Package

4.5.1 Oracle ROWID Type

A ROWID is an identification tag unique for each row of an Oracle Database table. The

ROWID can be thought of as a virtual column, containing the ID for each row.

The

oracle.sql.ROWID

class is supplied as a container for

ROWID

SQL data type.

ROWIDs provide functionality similar to the

getCursorName

method specified in the

java.sql.ResultSet

interface and the

setCursorName

method specified in the

java.sql.Statement

interface.

If you include the ROWID pseudo-column in a query, then you can retrieve the ROWIDs with

the result set

getString

method. You can also bind a ROWID to a

PreparedStatement

parameter with the

setString

method. This enables in-place updating, as in the example that

follows.

Note:

Use the

oracle.sql.ROWID

class, only when you are using J2SE 5.0. For JSE 6,

you should use the standard

java.sql.RowId

interface instead.

Example

The following example shows how to access and manipulate ROWID data:

Note:

The following example works only with JSE 6.

Statement stmt = conn.createStatement();

// Query the employee names with "FOR UPDATE" to lock the rows.

Chapter 4

Additional Oracle Type Extensions

4-17

// Select the ROWID to identify the rows to be updated.

ResultSet rset =

stmt.executeQuery ("SELECT first_name, rowid FROM employees FOR UPDATE");

// Prepare a statement to update the first_name column at a given ROWID

PreparedStatement pstmt =

conn.prepareStatement ("UPDATE employees SET first_name = ? WHERE rowid

= ?");

// Loop through the results of the query

while (rset.next ())

{

String ename = rset.getString (1);

RowId rowid = rset.getROWID(2); // Get the ROWID as a String

pstmt.setString (1, ename.toLowerCase ());

pstmt.setROWID (2, rowid); // Pass ROWID to the update statement

pstmt.executeUpdate (); // Do the update

}

4.5.2 Oracle REF CURSOR Type Category

A cursor variable holds the memory location of a query work area, rather than the

contents of the area. Declaring a cursor variable creates a pointer. In SQL, a pointer

has the data type

REF

, where

REF

is short for

REFERENCE

and

represents the entity

being referenced. A

REF CURSOR

, then, identifies a reference to a cursor variable.

Because many cursor variables might exist to point to many work areas,

REF

CURSOR

can be thought of as a category or data type specifier that identifies many different

types of cursor variables. Starting from Oracle Database Release 18 c, JDBC drivers

support

REF CURSOR

as IN bind variables.

Note:

REF CURSOR

instances are not scrollable.

Perform the following steps to create a cursor variable:

1. Identify a type that belongs to the

REF

CURSOR

category. For example:

DECLARE TYPE DeptCursorTyp IS REF CURSOR

2. Then, create the cursor variable by declaring it to be of the type

DeptCursorTyp

dept_cv DeptCursorTyp - - declare cursor variable

...

REF

CURSOR

, then, is a category of data types, rather than a particular data type.

Stored procedures can accept or return cursor variables of the

REF

CURSOR

category.

This output is equivalent to a database cursor or a JDBC result set. A

REF CURSOR

essentially encapsulates the results of a query.

In JDBC, a

REF CURSOR

can be accessed as follows:

Chapter 4

Additional Oracle Type Extensions

4-18

1. Use a JDBC callable statement or a prepared statement to call a stored procedure.

2. The stored procedure accepts or returns a

REF CURSOR

3. The Java application casts the callable statement or prepared statement to an Oracle

callable statement or Oracle prepared statement.

4. The Java application uses the

setCursor

method of the

OraclePreparedStatement

interface or the

getCursor

method of the

OracleCallableStatement

interface to

materialize the

REF CURSOR

as a JDBC

ResultSet

object.

5. The result set is processed as requested.

Note:

• The cursor associated with a

REF CURSOR

is closed whenever the statement

object that produced the

REF CURSOR

is closed.

• Unlike in past releases, the cursor associated with a

REF CURSOR

is not

closed when the result set object in which the

REF CURSOR

was materialized

is closed.

Example

This example shows how to access

REF CURSOR

data.

...

// Prepare a PL/SQL call

CallableStatement cstmt =

conn.prepareCall ("DECLARE rc sys_refcursor; curid NUMBER;BEGIN open

rc FOR SELECT empno FROM emp order by empno; ? := rc; END;");

cstmt.registerOutParameter (1, OracleTypes.CURSOR);

cstmt.execute ();

ResultSet rset = (ResultSet)cstmt.getObject (1);

if (rset.next ()) {

show (rset.getString ("empno"));

}

CallableStatement cstmt2 =

conn.prepareCall ("DECLARE rc sys_refcursor; v1 NUMBER; BEGIN

rc := ?; fetch rc INTO v1; ? := v1; END;");

((OracleCallableStatement)call2).setCursor(1, rset);

cstmt2.registerOutParameter (2, OracleTypes.INTEGER);

cstmt2.execute();

int empno = cstmt2.getInt(2);

show("Fetch in PL/SQL empno=" + empno);

// Dump the cursor

while (rset.next ())

Chapter 4

Additional Oracle Type Extensions

4-19

show (rset.getString ("empno"));

// Close all the resources

rset.close();

cstmt.close();

cstmt2.close();

...

In the preceding example:

• Two

CallableStatement

objects

cstmt1

and

cstmt2

are created using the

prepareCall

method of the

Connection

class.

• The

cstmt2

callable statement uses

REF CURSOR

as input parameter.

• The callable statements implement PL/SQL procedure that returns a

REF CURSOR

• As always, the output parameter of the callable statement must be registered to

define its type. Use the type code

OracleTypes.CURSOR

for a

REF CURSOR

• The callable statements are run, returning the

REF CURSOR

or sending the

REF

CURSOR

as input bind.

4.5.3 Oracle BINARY_FLOAT and BINARY_DOUBLE Types

The Oracle

BINARY_FLOAT

and

BINARY_DOUBLE

types are used to store IEEE 574 float

and double data. These correspond to the Java

float

and

double

scalar types with

the exception of negative zero and

NaN

See Also:

Oracle Database SQL Language Reference

If you include a

BINARY_DOUBLE

column in a query, then the data is retrieved from the

database in the binary format. Also, the

getDouble

method will return the data in the

binary format. In contrast, for a

NUMBER

data type column, the number bits are returned

and converted to the Java

double

data type.

Note:

The Oracle representation for the SQL

FLOAT

DOUBLE PRECISION

, and

REAL

data types use the Oracle

NUMBER

representation. The

BINARY_FLOAT

and

BINARY_DOUBLE

data types can be regarded as proprietary types.

A call to the JDBC standard

setDouble(int, double)

method of the

PreparedStatement

interface converts the Java

double

argument to Oracle

NUMBER

style bits and send them to the database. In contrast, the

setBinaryDouble(int,

double)

method of the

oracle.jdbc.OraclePreparedStatement

interface converts the

data to the internal binary bits and sends them to the database.

Chapter 4

Additional Oracle Type Extensions

4-20

You must ensure that the data format used matches the type of the target parameter of the

PreparedStatement

interface. This will result in correct data and least use of CPU. If you use

setBinaryDouble

for a

NUMBER

parameter, then the binary bits are sent to the server and

converted to

NUMBER

format. The data will be correct, but server CPU load will be increased. If

you use

setDouble

for a

BINARY_DOUBLE

parameter, then the data will first be converted to

NUMBER

bits on the client and sent to the server, where it will be converted back to binary

format. This will increase the CPU load on both client and server and can result in data

corruption as well.

The

SetFloatAndDoubleUseBinary

connection property when set to

true

causes the JDBC

standard APIs,

setFloat(int,

float)

setDouble(int,

double)

, and all the variations, to

send internal binary bits instead of

NUBMER

bits.

Note:

Although this section largely discusses

BINARY_DOUBLE

, the same is true for

BINARY_FLOAT

as well.

4.5.4 Oracle SYS.ANYTYPE and SYS.ANYDATA Types

Oracle Database 12c Release 1 (12.1) provides a Java interface to access the

SYS.ANYTYPE

and

SYS.ANYDATA

Oracle types.

See Also:

For information about these Oracle types, refer Oracle Database PL/SQL Packages

and Types Reference

An instance of the

SYS.ANYTYPE

type contains a type description of any SQL type, persistent

or transient, named or unnamed, including object types and collection types. You can use the

oracle.sql.TypeDescriptor

class to access the

SYS.ANYTYPE

type. An

ANYTYPE

instance can

be retrieved from a PL/SQL procedure or a SQL

SELECT

statement where

SYS.ANYTYPE

used as a column type. To retrieve an

ANYTYPE

instance from the database, use the

getObject

method. This method returns an instance of the

TypeDescriptor

The retrieved

ANYTYPE

instance could be any of the following:

• Transient object type

• Transient predefined type

• Persistent object type

• Persistent predefined type

Example 4-1 Accessing SYS.ANYTYPE Type

The following code snippet illustrates how to retrieve an instance of

ANYTYPE

from the

database:

...

ResultSet rs = stmt.executeQuery("select anytype_column from my_table");

Chapter 4

Additional Oracle Type Extensions

4-21

TypeDescriptor td = (TypeDescriptor)rs.getObject(1);

short typeCode = td.getInternalTypeCode();

if(typeCode == TypeDescriptor.TYPECODE_OBJECT)

{

// check if it's a transient type

if(td.isTransientType())

{

AttributeDescriptor[] attributes =

((StructDescriptor)td).getAttributesDescriptor();

for(int i=0; i<attributes.length; i++)

System.out.println(attributes[i].getAttributeName());

}

else

{ System.out.println(td.getTypeName()); }}

...

Example 4-2 Creating a Transient Object Type Through PL/SQL and Retrieving

Through JDBC

This example provides a code snippet illustrating how to retrieve a transient object

type through JDBC.

...

OracleCallableStatement cstmt = (OracleCallableStatement)conn.prepareCall

("BEGIN ? := transient_obj_type (); END;");

cstmt.registerOutParameter(1,OracleTypes.OPAQUE,"SYS.ANYTYPE");

cstmt.execute();

TypeDescriptor obj = (TypeDescriptor)cstmt.getObject(1);

if(!obj.isTransient())

System.out.println("This must be a JDBC bug");

cstmt.close();

return obj;

...

Example 4-3 Calling a PL/SQL Stored Procedure That Takes an ANYTPE as IN

Parameter

The following code snippet illustrates how to call a PL/SQL stored procedure that

takes an

ANYTYPE

parameter:

...

CallableStatement cstmt = conn.prepareCall("BEGIN ? := dumpanytype(?); END;");

cstmt.registerOutParameter(1,OracleTypes.VARCHAR);

// obj is the instance of TypeDescriptor that you have retrieved

cstmt.setObject(2,obj);

cstmt.execute();

String str = (String)cstmt.getObject(1);

...

The

oracle.sql.ANYDATA

class enables you to access

SYS.ANYDATA

instances from

the database. An instance of this class can be obtained from any valid instance of

oracle.sql.Datum

class. The

convertDatum

factory method takes an instance of

Datum

and returns an instance of

ANYDATA

. The syntax for this factory method is as

follows:

public static ANYDATA convertDatum(Datum datum) throws SQLException

The following is sample code for creating an instance of

oracle.sql.ANYDATA

Chapter 4

Additional Oracle Type Extensions

4-22

// struct is a valid instance of oracle.sql.STRUCT that either comes from the

// database or has been constructed in Java.

ANYDATA myAnyData = ANYDATA.convertDatum(struct);

Example 4-4 Accessing an Instance of ANYDATA from the Database

...

// anydata_table has been created as:

// CREATE TABLE anydata_tab (data SYS.ANYDATA)

Statement stmt = conn.createStatement();

ResultSet rs = stmt.executeQuery("select data from my_anydata_tab");

while(rs.next())

{

ANYDATA anydata = (ANYDATA)rs.getObject(1);

if(!anydata.isNull())

{

TypeDescriptor td = anydata.getTypeDescriptor();

if(td.getTypeCode() == OracleType.TYPECODE_OBJECT)

STRUCT struct = (STRUCT)anydata.accessDatum();

}

...

Example 4-5 Inserting an Object as ANYDATA in a Database Table

Consider the following table and object type definition:

CREATE TABLE anydata_tab ( id NUMBER, data SYS.ANYDATA)

CREATE OR REPLACE TYPE employee AS OBJECT ( employee_id NUMBER, first_name

VARCHAR2(10) )

You can create an instance of the

EMPLOYEE

SQL object type and to insert it into

anydata_tab

le in the following way:

...

PreparedStatement pstmt = conn.prepareStatement("insert into anydata_table values

(?,?)");

Struct myEmployeeStr = conn.createStruct("EMPLOYEE", new Object[]{1120, "Papageno"});

ANYDATA anyda = ANYDATA.convertDatum(myEmployeeStr);

pstmt.setInt(1,123);

pstmt.setObject(2,anyda);

pstmt.executeUpdate();

...

Example 4-6 Selecting an ANYDATA Column from a Database Table

...

Statement stmt = conn.createStatement();

ResultSet rs = stmt.executeQuery("select data from anydata_table");

while(rs.next())

{

ANYDATA obj = (ANYDATA)rs.getObject(1);

TypeDescriptor td = obj.getTypeDescriptor();

}

rs.close();

stmt.close();

...

Chapter 4

Additional Oracle Type Extensions

4-23

4.5.5 The oracle.jdbc Package

The interfaces of the

oracle.jdbc

package define the Oracle extensions to the

interfaces in

java.sql

. These extensions provide access to SQL-format data as

described in this chapter. They also provide access to other Oracle-specific

functionality, including Oracle performance enhancements.

For the

oracle.jdbc

package, Table 4-1 lists key interfaces and classes used for

connections, statements, and result sets.

Table 4-1 Key Interfaces and Classes of the oracle.jdbc Package

Name Interface

or Class

Key Functionality

OracleDriver

Class Implements

java.sql.Driver

OracleConnection

Interface Provides methods to start and stop an

Oracle Database instance and to return

Oracle statement objects and methods to

set Oracle performance extensions for any

statement run in the current connection.

Implements

java.sql.Connection.

OracleStatement

Interface Provides methods to set Oracle

performance extensions for individual

statement.

Is a supertype of

OraclePreparedStatement

and

OracleCallableStatement

Implements

java.sql.Statement.

OraclePreparedStatement

Interface Provides

setXXX

methods to bind

oracle.sql.*

types into a prepared

statement.

Provides

getMetaData

method to get the

metadata from the prepared statements

without executing the SELECT statements.

Implements

java.sql.PreparedStatement.

Extends

OracleStatement.

Is a supertype of

OracleCallableStatement

Interface Provides

getXXX

methods to retrieve data

oracle.sql

format and

setXXX

methods to bind

oracle.sql.*

types into

a callable statement.

Implements

java.sql.CallableStatement.

Extends

OraclePreparedStatement.

OracleResultSet

Interface Provides

getXXX

methods to retrieve data

oracle.sql

format.

Implements

java.sql.ResultSet

Chapter 4

Additional Oracle Type Extensions

4-24

Table 4-1 (Cont.) Key Interfaces and Classes of the oracle.jdbc Package

Name Interface

or Class

Key Functionality

OracleResultSetMetaData

Interface Provides methods to get metadata

information about Oracle result sets, such

as column names and data types.

Implements

java.sql.ResultSetMetaData

OracleDatabaseMetaData

Class Provides methods to get metadata

information about the database, such as

database product name and version, table

information, and default transaction

isolation level.

Implements

java.sql.DatabaseMetaData

OracleTypes

Class Defines integer constants used to identify

SQL types.

For standard types, it uses the same values

as the standard

java.sql.Types

class. In

addition, it adds constants for Oracle

extended types.

OracleArray

Interface Includes functionality to retrieve the array

as a whole, retrieve a subset of the array

elements, and retrieve the SQL base type

name of the array elements.

OracleStruct

Interface

OracleClob

Interface

OracleBlob

Interface

OracleRef

Interface

OracleOpaque

Interface

This section covers the following topics:

• Interface oracle.jdbc.OracleConnection

• Interface oracle.jdbc.OracleStatement

• Interface oracle.jdbc.OraclePreparedStatement

• Interface oracle.jdbc.OracleCallableStatement

• Interface oracle.jdbc.OracleResultSet

• Interface oracle.jdbc.OracleResultSetMetaData

• Class oracle.jdbc.OracleTypes

4.5.5.1 Interface oracle.jdbc.OracleConnection

This interface extends standard JDBC connection functionality to create and return Oracle

statement objects, set flags and options for Oracle performance extensions, support type

maps for Oracle objects, and support client identifiers.

Chapter 4

Additional Oracle Type Extensions

4-25

In Oracle Database 11g Release 1, new methods were added to this interface that

enable the starting up and shutting down of an Oracle Database instance. Also, for

better visibility and clarity, all connection properties are defined as constants in the

OracleConnection

interface.

This interface also defines factory methods for constructing

oracle.sql

data values

DATE

and

NUMBER

. Remember the following points while using factory methods:

• All code that constructs instances of the

oracle.sql

types should use the Oracle

extension factory methods. For example,

ARRAY

BFILE

DATE

INTERVALDS

NUMBER

STRUCT

TIME

TIMESTAMP

, and so on.

• All code that constructs instances of the standard types should use the JDBC 4.0

standard factory methods. For example,

CLOB

BLOB

NCLOB

, and so on.

• There are no factory methods for

CHAR

JAVA_STRUCT

ArrayDescriptor

, and

StructDescriptor.

These types are for internal driver use only.

Note:

Prior to Oracle Database 11g Release 1, you had to construct

ArrayDescriptors

and

StructDescriptors

for passing as arguments to

the

ARRAY

and

STRUCT

class constructors. The new

ARRAY

and

Struct

factory methods do not have any descriptor arguments. The driver still

uses descriptors internally, but you do not need to create them.

Client Identifiers

In a connection pooling environment, the client identifier can be used to identify the

lightweight user using the database session currently. A client identifier can also be

used to share the Globally Accessed Application Context between different database

sessions. The client identifier set in a database session is audited when database

auditing is turned on.

See Also:

Oracle Database JDBC Java API Reference for more information

4.5.5.2 Interface oracle.jdbc.OracleStatement

This interface extends standard JDBC statement functionality and is the superinterface

of the

OraclePreparedStatement

and

OracleCallableStatement

classes. Extended

functionality includes support for setting flags and options for Oracle performance

extensions on a statement-by-statement basis, as opposed to the

OracleConnection

interface that sets these on a connectionwide basis.

4.5.5.3 Interface oracle.jdbc.OraclePreparedStatement

This interface extends the

OracleStatement

interface and extends standard JDBC

prepared statement functionality. Also, the

oracle.jdbc.OraclePreparedStatement

Chapter 4

Additional Oracle Type Extensions

4-26

interface is extended by the

OracleCallableStatement

interface. Extended functionality

consists of the following:

•

setXXX

methods for binding

oracle.sql.*

types and objects to prepared statements

•

getMetaData

method to get the metadata from the prepared statements without executing

the SELECT statements

• Methods to support Oracle performance extensions on a statement-by-statement basis

Note:

Do not use the

PreparedStatement

interface to create a trigger that refers to a

:NEW

:OLD

column. Use

Statement

instead. Using

PreparedStatement

will cause

execution to fail with the message

java.sql.SQLException: Missing IN or OUT

parameter at index:: 1

4.5.5.4 Interface oracle.jdbc.OracleCallableStatement

This interface extends the

OraclePreparedStatement

interface, which extends the

OracleStatement

interface and incorporates standard JDBC callable statement functionality.

Note:

Do not use the

CallableStatement

interface to create a trigger that refers to a

:NEW

:OLD

column. Use

Statement

instead; using

CallableStatement

will cause

execution to fail with the message

java.sql.SQLException: Missing IN or OUT

parameter at index::1

Note:

• The

setXXX(String,...)

and

registerOutParameter(String,...)

methods

can be used only if all binds are procedure or function parameters only. The

statement can contain no other binds and the parameter binds must be

indicated with a question mark (

and not

:XX

• If you are using

setXXX(int,...) or

setXXXAtName(String,...)

method, then

any output parameter is bound with

registerOutParameter(int,...)

and not

registerOutParameter(String,...)

, which is for named parameter notation.

4.5.5.5 Interface oracle.jdbc.OracleResultSet

This interface extends standard JDBC result set functionality, implementing

getXXX

methods

for retrieving data into

oracle.sql.*

objects.

Chapter 4

Additional Oracle Type Extensions

4-27

4.5.5.6 Interface oracle.jdbc.OracleResultSetMetaData

This interface extends standard JDBC result set metadata functionality to retrieve

information about Oracle result set objects.

See Also:

"Using Result Set Metadata Extensions"

4.5.5.7 Class oracle.jdbc.OracleTypes

The

OracleTypes

class defines constants that JDBC uses to identify SQL types. Each

variable in this class has a constant integer value. The

oracle.jdbc.OracleTypes

class duplicates the type code definitions of the standard Java

java.sql.Types

class

and contains these additional type codes for Oracle extensions:

•

OracleTypes.BFILE

•

OracleTypes.ROWID

•

OracleTypes.CURSOR

(for

REF CURSOR

types)

•

OracleTypes.CHAR_BYTES

(for calling

setNull

and

setCHAR

methods on the same

column)

As in

java.sql.Types

, all the variable names are in uppercase text.

JDBC uses the SQL types identified by the elements of the

OracleTypes

class in two

main areas: registering output parameters and in the

setNull

method of the

PreparedStatement

class.

OracleTypes and Registering Output Parameters

The type codes in

java.sql.Types

oracle.jdbc.OracleTypes

identify the SQL

types of the output parameters in the

registerOutParameter

method of the

java.sql.CallableStatement

and

oracle.jdbc.OracleCallableStatement

interfaces.

These are the forms that the

registerOutputParameter

method can take for the

CallableStatement

and

OracleCallableStatement

interfaces

cs.registerOutParameter(int index, int sqlType);

cs.registerOutParameter(int index, int sqlType, String sql_name);

cs.registerOutParameter(int index, int sqlType, int scale);

In these signatures,

index

represents the parameter index,

sqlType

is the type code

for the SQL data type,

sql_name

is the name given to the data type, for user-defined

types, when

sqlType

is a

STRUCT

REF

, or

ARRAY

type code, and

scale

represents the

number of digits to the right of the decimal point, when

sqlType

is a

NUMERIC

DECIMAL

type code.

Chapter 4

Additional Oracle Type Extensions

4-28

The following example uses a

CallableStatement

interface to call a procedure named

charout

, which returns a

CHAR

data type. Note the use of the

OracleTypes.CHAR

type code in

the

registerOutParameter

method.

CallableStatement cs = conn.prepareCall ("BEGIN charout (?); END;");

cs.registerOutParameter (1, OracleTypes.CHAR);

cs.execute ();

System.out.println ("Out argument is: " + cs.getString (1));

The next example uses a

CallableStatement

interface to call

structout

, which returns a

STRUCT

data type. The form of

registerOutParameter

requires you to specify the type code,

Types.STRUCT

OracleTypes.STRUCT

, as well as the SQL name,

EMPLOYEE

The example assumes that no type mapping has been declared for the

EMPLOYEE

type, so it is

retrieved into a

STRUCT

data type. To retrieve the value of

EMPLOYEE

as an

oracle.sql.STRUCT

object, the statement object

is cast to

OracleCallableStatement

and the Oracle extension

getSTRUCT

method is invoked.

CallableStatement cs = conn.prepareCall ("BEGIN structout (?); END;");

cs.registerOutParameter (1, OracleTypes.STRUCT, "EMPLOYEE");

cs.execute ();

// get the value into a STRUCT because it

// is assumed that no type map has been defined

STRUCT emp = ((OracleCallableStatement)cs).getSTRUCT (1);

OracleTypes and the setNull Method

The type codes in

Types

and

OracleTypes

identify the SQL type of the data item, which the

setNull

method sets to

NULL

. The

setNull

method can be found in the

java.sql.PreparedStatement

and

oracle.jdbc.OraclePreparedStatement

interfaces.

These are the forms that the

setNull

method can take for the

PreparedStatement

and

OraclePreparedStatement

objects:

ps.setNull(int index, int sqlType);

ps.setNull(int index, int sqlType, String sql_name);

In these signatures,

index

represents the parameter index,

sqlType

is the type code for the

SQL data type, and

sql_name

is the name given to the data type, for user-defined types,

when

sqlType

is a

STRUCT

REF

, or

ARRAY

type code. If you enter an invalid

sqlType

, a

ParameterTypeConflict

exception is thrown.

The following example uses a prepared statement to insert a null value into the database.

Note the use of

OracleTypes.NUMERIC

to identify the numeric object set to

NULL

. Alternatively,

Types.NUMERIC

can be used.

PreparedStatement pstmt =

conn.prepareStatement ("INSERT INTO num_table VALUES (?)");

pstmt.setNull (1, OracleTypes.NUMERIC);

pstmt.execute ();

In this example, the prepared statement inserts a

NULL

STRUCT

object of type

EMPLOYEE

into

the database.

PreparedStatement pstmt = conn.prepareStatement

("INSERT INTO employees VALUES (?)");

Chapter 4

Additional Oracle Type Extensions

4-29

pstmt.setNull (1, OracleTypes.STRUCT, "EMPLOYEE");

pstmt.execute ();

You can also use the

OracleTypes.CHAR_BYTES

type with the

setNull

method, if you

also want to call the

setCHAR

method on the same column. For example:

ps.setCHAR(n, aCHAR);

ps.addBatch();

ps.setNull(n, OracleTypes.CHAR_BYTES);

ps.addBatch();

In this preceding example, any other type, apart from the

OracleTypes.CHAR_BYTES

type, will cause extra round trips to the Database. Alternatively, you can also write your

code without using the

setNull

method. For example, you can also write your code as

shown in the following example:

ps.setCHAR(n, null);

4.6 DML Returning

The DML returning feature provides more functionality compared to retrieval of auto-

generated keys. It can be used to retrieve not only auto-generated keys, but also other

columns or values that the application may use.

Note:

• The server-side internal driver does not support DML returning and

retrieval of auto-generated keys.

• You cannot use both DML returning and retrieval of auto-generated keys

in the same statement.

The following sections explain the support for DML returning:

• Oracle-Specific APIs

• About Running DML Returning Statements

• Example of DML Returning

• Limitations of DML Returning

4.6.1 Oracle-Specific APIs

The

OraclePreparedStatement

interface is enhanced with Oracle-specific application

programming interfaces (APIs) to support DML returning. The

registerReturnParameter

and

getReturnResultSet

methods have been added to the

oracle.jdbc.OraclePreparedStatement

interface, to register parameters that are

returned and data retrieved by DML returning.

The

registerReturnParameter

method is used to register the return parameter for

DML returning. The method throws a

SQLException

instance if an error occurs. You

must pass a positive integer specifying the index of the return parameter. You also

must specify the type of the return parameter. You can also specify the maximum

Chapter 4

DML Returning

4-30

bytes or characters of the return parameter. This method can be used only with

char

RAW

types. You can also specify the fully qualified name of a SQL structure type.

Note:

If you do not know the maximum size of the return parameters, then you should use

registerReturnParameter(int paramIndex, int externalType)

, which picks the

default maximum size. If you know the maximum size of return parameters, using

registerReturnParameter(int paramIndex, int externalType, int maxSize)

can reduce memory consumption.

The

getReturnResultSet

method fetches the data returned from DML returning and returns it

as a

ResultSet

object. The method throws a

SQLException

exception if an error occurs.

Note:

The Oracle-specific APIs for the DML returning feature are in

ojdbc6.jar

for Java

Development Kit (JDK) 6.0 and in

ojdbc7.jar

for JDK 7.

4.6.2 About Running DML Returning Statements

Before running a DML returning statement, the JDBC application must call one or more of the

registerReturnParameter

methods. The method provides the JDBC drivers with information,

such as type and size, of the return parameters. The DML returning statement is then

processed using one of the standard JDBC APIs,

executeUpdate

execute

. You can then

fetch the returned parameters as a

ResultSet

object using the

getReturnResultSet

method

of the

oracle.jdbc.OraclePreparedStatement

interface.

In order to read the values in the

ResultSet

object, the underlying

Statement

object must be

open. When the underlying

Statement

object is closed, the returned

ResultSet

object is also

closed. This is consistent with

ResultSet

objects that are retrieved by processing SQL query

statements.

When a DML returning statement is run, the concurrency of the

ResultSet

object returned by

the

getReturnResultSet

method must be

CONCUR_READ_ONLY

and the type of the

ResultSet

object must be

TYPE_FORWARD_ONLY

TYPE_SCROLL_INSENSITIVE

4.6.3 Example of DML Returning

This section provides two code examples of DML returning.

The following code example illustrates the use of DML returning. In this example, assume

that the maximum size of the

name

column is 100 characters. Because the maximum size of

the

name

column is known, the

registerReturnParameter(int paramIndex, int

externalType, int maxSize)

method is used.

...

OraclePreparedStatement pstmt = (OraclePreparedStatement)conn.prepareStatement(

"delete from tab1 where age < ? returning name into ?");

Chapter 4

DML Returning

4-31

pstmt.setInt(1,18);

/** register returned parameter

* in this case the maximum size of name is 100 chars

pstmt.registerReturnParameter(2, OracleTypes.VARCHAR, 100);

// process the DML returning statement

count = pstmt.executeUpdate();

if (count>0)

{

ResultSet rset = pstmt.getReturnResultSet(); //rest is not null and not empty

while(rset.next())

{

String name = rset.getString(1);

...

}

...

The following code example also illustrates the use of DML returning. However, in this

case, the maximum size of the return parameters is not known. Therefore, the

registerReturnParameter(int paramIndex, int externalType)

method is used.

...

OraclePreparedStatement pstmt = (OraclePreparedStatement)conn.prepareStatement(

"insert into lobtab values (100, empty_clob()) returning col1, col2

into ?, ?");

// register return parameters

pstmt.registerReturnParameter(1, OracleTypes.INTEGER);

pstmt.registerReturnParameter(2, OracleTypes.CLOB);

// process the DML returning SQL statement

pstmt.executeUpdate();

ResultSet rset = pstmt.getReturnResultSet();

int r;

CLOB clob;

if (rset.next())

{

r = rset.getInt(1);

System.out.println(r);

clob = (CLOB)rset.getClob(2);

...

}

...

4.6.4 Limitations of DML Returning

When using DML returning, be aware of the following:

• It is unspecified what the

getReturnResultSet

method returns when it is invoked

more than once. You should not rely on any specific action in this regard.

• The

ResultSet

objects returned from the execution of DML returning statements

do not support the

ResultSetMetaData

type. Therefore, the applications must

know the information of return parameters before running DML returning

statements.

• Streams are not supported with DML returning.

Chapter 4

DML Returning

4-32

• DML returning cannot be combined with batch update.

• You cannot use both the auto-generated key feature and the DML returning feature in a

single SQL DML statement. For example, the following is not allowed:

...

PreparedStatement pstmt = conn.prepareStatement('insert into orders (?, ?, ?)

returning order_id into ?");

pstmt.setInt(1, seq01.NEXTVAL);

pstmt.setInt(2, 100);

pstmt.setInt(3, 966431502);

pstmt.registerReturnParam(4, OracleTypes.INTEGER);

pstmt.executeUpdate;

ResultSet rset = pstmt.getGeneratedKeys;

...

4.7 Accessing PL/SQL Associative Arrays

Oracle JDBC drivers enable JDBC applications to make PL/SQL calls with Associative Arrays

parameters. This section describes the methods to access Associative Arrays.

In PL/SQL, an Associative Array is a set of key-value pairs, where the keys may be

PLS_INTEGER

s or Strings. The keys may have any value and need not be dense. From a client

application, you can work only with

PLS_INTEGER

BINARY_INTEGER

keys.

Note:

• Associative Arrays were previously known as index-by tables.

• The

PLS_INTEGER

and

BINARY_INTEGER

are identical data types.

• When you use String data types, the size is limited to the size in PL/SQL that is

32767 characters. For the server-side internal driver, the limits are lower.

The previous release of Oracle JDBC drivers provided support only for PL/SQL Associative

Arrays of Scalar data types. Also, the support was restricted only to the values of the key-

value pairs of the Arrays. Starting from Release 18c, Oracle Database supports accessing

both the keys (indexes) and values of Associative Arrays, and also provides support for

Associative Arrays of object types. Use the following methods to achieve the new

functionalities:

•

Array createOracleArray(String arrayTypeName,

Object elements)

throws SQLException

•

ARRAY createARRAY(String typeName,

Object elements)

throws SQLException

Chapter 4

Accessing PL/SQL Associative Arrays

4-33

Note:

You can use the

createOracleArray

method and the

createARRAY

method for Associative Arrays on Oracle Database release 12c and later

releases. If you are using an earlier release of Oracle Database, then

you should continue using the following deprecated APIs:

–

oracle.jdbc.OraclePreparedStatement.setPlsqlIndexTable

–

oracle.jdbc.OracleCallableStatement.getPlsqlIndexTable

–

oracle.jdbc.OracleCallableStatement.getOraclePlsqlIndexTabl

–

oracle.jdbc.OracleCallableStatement.registerIndexTableOutPa

rameter

In both the preceding methods, the second parameter can either be a

java.util.Map<Integer, ?>

that holds the key-value pairs of the Associative

Arrays, or it can only be an array of values. If it is an array of values, then the

JDBC driver defaults the indexes to 0,1,2 and so on. If it is

java.util.Map<Integer, ?>

, then the JDBC driver does not default the keys.

They remain as specified in the Map, and can be sparse and negative.

•

Map<?,?> oracle.jdbc.OracleArray.getJavaMap();

This method returns a

Map<?,?>

for the data types in the Associative Array and

null

for Nested Tables and VARRAYs.

See Also:

• Oracle Database JDBC Java API Reference

• Oracle Database PL/SQL Language Reference for more information

about Associative Arrays

Chapter 4

Accessing PL/SQL Associative Arrays

4-34

Features Specific to JDBC Thin

This chapter introduces the Java Database Connectivity (JDBC) Thin client and covers the

following features supported only by the JDBC Thin driver:

• Overview of JDBC Thin Client

• Additional Features Supported

5.1 Overview of JDBC Thin Client

The JDBC Thin client is a pure Java, Type IV driver. It is lightweight and easy to install. It

provides high performance, comparable to the performance provided by the JDBC Oracle

Call Interface (OCI) driver. The JDBC Thin driver is written entirely in Java, and therefore, it is

platform-independent. Also, this driver does not require any additional Oracle software on the

client-side.

The JDBC Thin driver communicates with the server using TTC, a protocol developed by

Oracle to access data from Oracle Database. It can be used for application servers. The

driver allows a direct connection to the database by providing an implementation of TCP/IP

that implements Oracle Net and TTC on top of Java sockets. Both of these protocols are

lightweight implementation versions of their counterparts on the server. The Oracle Net

protocol runs over TCP/IP only.

The JDBC Thin driver can be used on both the client-side and the server-side. On the client-

side, drivers can be used in Java applications that run either on the client or in the middle tier

of a three-tier configuration. On the server-side, this driver is used to access a remote Oracle

Database instance or another session on the same database.

5.2 Additional Features Supported

The JDBC Thin driver supports all standard JDBC features. The JDBC Thin driver also

provides support for the following additional features:

• Default Support for Native XA

• Support for Transaction Guard

• Support for Application Continuity

5.2.1 Default Support for Native XA

Similar to the JDBC OCI driver, the JDBC Thin driver also provides support for Native XA.

However, the JDBC Thin driver provides support for Native XA by default. This is unlike the

case of the JDBC OCI driver, in which the support for Native XA is not enabled by default.

5-1

See Also:

"Native-XA in Oracle JDBC Drivers"

5.2.2 Support for Transaction Guard

Transaction Guard feature provides a generic infrastructure for at-most-once execution

during planned and unplanned outages and duplicate submissions. Transaction Guard

feature (along with Application Continuity feature) provides transparent session

recovery and replay of SQL statements (queries and DMLs) since the beginning of the

in-flight transaction.

See Also:

Transaction Guard for Java

5.2.3 Support for Application Continuity

Application Continuity provides a general purpose, application-independent

infrastructure that enables recovery of work from an application perspective, after the

occurrence of a planned or unplanned outage. It provides the following benefits:

• Masking of outages from the end user

• Recovery of user environments, in-flight transactions, and lost outcome

• A single, easy, and foolproof method for applications to recover

• A definite target response time for applications, regardless of outages

See Also:

Application Continuity for Java

Chapter 5

Additional Features Supported

5-2

Features Specific to JDBC OCI Driver

This chapter introduces the features specific to the Java Database Connectivity (JDBC)

Oracle Call Interface (OCI) driver. It also describes the OCI Instant Client. This chapter

contains the following sections:

• OCI Connection Pooling

• Transparent Application Failover

• OCI Native XA

• OCI Instant Client

• About Instant Client Light (English)

6.1 OCI Connection Pooling

The OCI connection pooling feature is an Oracle-designed extension. The connection pooling

provided by the JDBC OCI driver enables applications to have multiple logical connections,

all of which are using a small set of physical connections. Each call on a logical connection is

routed on to the physical connection that is available at the given time.

See Also:

OCI Connection Pooling

6.2 Transparent Application Failover

The Transparent Application Failover feature of JDBC OCI driver enables you to

automatically reconnect to a database if the database instance to which the connection is

made goes down. The new database connection, though created by a different node, is

identical to the original.

See Also:

Transparent Application Failover

6.3 OCI Native XA

The JDBC OCI driver also provides a feature called Native XA. This feature enables to use

native APIs to send XA commands. The native APIs provide high performance gains as

compared to non-native APIs.

6-1

Related Topics

• OCI Native XA

6.4 OCI Instant Client

This section covers the following topics:

• Overview of Instant Client

• OCI Instant Client Shared Libraries

• Benefits of Instant Client

• JDBC OCI Instant Client Installation Process

• Usage of Instant Client

• About Patching Instant Client Shared Libraries

• Regeneration of Data Shared Library and ZIP files

• Database Connection Names for OCI Instant Client

• Environment Variables for OCI Instant Client

6.4.1 Overview of Instant Client

The Instant Client is packaged in a way that makes it extremely easy to deploy OCI,

Oracle C++ Call Interface (OCCI), Open Database Connectivity (ODBC), and JDBC-

OCI based customer applications, by eliminating the need for an Oracle home. The

storage space requirement of a JDBC OCI application using the Instant Client is

significantly reduced compared to the same application running on a full client-side

installation. The Instant Client shared libraries occupy only about one-fourth the disk

space used by a full client installation.

6.4.2 OCI Instant Client Shared Libraries

You must have the Oracle client-side files required to deploy a JDBC OCI application.

The library names mentioned in this table correspond to Oracle Database Release

21c. The number part of library names change with every release to agree with the

release.

Table 6-1 OCI Instant Client Shared Libraries

Linux and UNIX

Systems

Description for Linux and

UNIX Systems

Microsoft

Windows

Description for Microsoft

Windows

libclntsh.so.21.

libclntshcore.so

.21.1

Client Code Library

oci.dll

Forwarding functions that

applications link with

libociei.so

OCI Instant Client Data Shared

Library

oraociei21.dll

Data and code

libnnz21.so

Security Library

orannzsbb21.dll

Security Library

libocijdbc21.so

OCI Instant Client JDBC Library

ocijdbc21.dll

OCI Instant Client JDBC Library

Chapter 6

OCI Instant Client

6-2

Table 6-1 (Cont.) OCI Instant Client Shared Libraries

Linux and UNIX

Systems

Description for Linux and

UNIX Systems

Microsoft

Windows

Description for Microsoft

Windows

ALL JDBC Java

Archive (JAR) files

Related Topics

• JDBC OCI Instant Client Installation Process

The Instant Client libraries can be installed by choosing the Instant Client option

from Oracle Universal Installer.

6.4.7 Regeneration of Data Shared Library and ZIP files

The OCI Instant Client Data Shared Library,

libociei.so

, can be regenerated by

performing the following steps in an Administrator Installation of

ORACLE_HOME

mkdir -p $ORACLE_HOME/rdbms/install/instantclient/light

cd $ORACLE_HOME/rdbms/lib

make -f ins_rdbms.mk ilibociei

A new version of the

libociei.so

Data Shared Library based on the current files in

the

ORACLE_HOME

is then placed in the

ORACLE_HOME/rdbms/install/instantclient

directory.

Note that the location of the regenerated Data Shared Library,

libociei.so

, is

different from that of the original Data Shared Library,

libociei.so

, which is located in

the

ORACLE_HOME/instantclient

directory. The preceding steps also generate Instant

Client ZIP files for OCI, OCCI, JDBC, and SQL*Plus.

Regeneration of data shared library and ZIP files is not available on Microsoft

Windows platforms.

6.4.8 Database Connection Names for OCI Instant Client

All Oracle Net naming methods that do not require the

ORACLE_HOME

TNS_ADMIN

environment variables to locate configuration files, such as

tnsnames.ora

sqlnet.ora

, use the Instant Client. In particular, the connection string can be specified

in the following formats:

• A Thin-style connection string of the form:

host:port:service_name

For example:

url="jdbc:oracle:oci:@example.com:5521:orcl"

• A SQL connection URL string of the form:

//host:[port][/service_name]

Chapter 6

OCI Instant Client

6-6

For example:

url="jdbc:oracle:oci:@//example.com:5521/orcl"

• As an Oracle Net keyword-value pair. For example:

url="jdbc:oracle:oci:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)

(HOST=localhost) (PORT=5521))

(CONNECT_DATA=(SERVICE_NAME=orcl)))"

Naming methods that require

TNS_ADMIN

to locate configuration files continue to work if the

TNS_ADMIN

environment variable is set.

See Also:

Oracle Database Net Services Administrator's Guide for more information about

connection formats

If the

TNS_ADMIN

environment variable is not set and

TNSNAMES

entries, such as

inst1

, are

used, then the

ORACLE_HOME

environment variable must be set and the configuration files are

expected to be in the

$ORACLE_HOME/network/admin

directory.

Note:

In this case, the

ORACLE_HOME

environment variable is used only for locating Oracle

Net configuration files. No other component of Client Code Library uses the value of

the

ORACLE_HOME

environment variable.

The empty connection string is not supported. However, an alternate way to use the empty

connection string is to set the

TWO_TASK

environment variable on UNIX systems, or the

LOCAL

variable on Microsoft Windows, to either a

tnsnames.ora

entry or an Oracle Net keyword-

value pair. If

TWO_TASK

LOCAL

is set to a

tnsnames.ora

entry, then the

tnsnames.ora

file

must be loaded by the

TNS_ADMIN

ORACLE_HOME

setting.

Example

Consider that the

listener.ora

file on the database server contains the following

information:

LISTENER = (ADDRESS_LIST=(ADDRESS=(PROTOCOL=tcp)(HOST=server6)(PORT=5221)))

SID_LIST_LISTENER = (SID_LIST=

(SID_DESC=(SID_NAME=rdbms3)

(GLOBAL_DBNAME=rdbms3.server6.com)

(ORACLE_HOME=/home/dba/rdbms3/oracle)))

You can connect to this server in one of the following ways:

url = "jdbc:oracle:oci:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)

(HOST=server6)(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=rdbms3.server6.com)))"

or:

Chapter 6

OCI Instant Client

6-7

url = "jdbc:oracle:oci:@//server6:5221/rdbms3.server6.com"

Alternatively, you can set the

TWO_TASK

environment variable to any of the connection

strings and connect to the database server without specifying the connection string

along with the

sqlplus

command. For example, set the

TWO_TASK

environment in one

of the following ways:

setenv TWO_TASK "(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=server6)(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=rdbms3.server6.com)))"

or:

setenv TWO_TASK //server6:5221/rdbms3.server6.com

Now, you can connect to the database server using the following URL:

url = "jdbc:oracle:oci:@"

The connection string can also be stored in the

tnsnames.ora

file. For example,

consider that the

tnsnames.ora

file contains the following:

conn_str = (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=server6)(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=rdbms3.server6.com)))

If this

tnsnames.ora

file is located in the

/home/webuser/instantclient

directory, then

you can set the

TNS_ADMIN

environment variable (or

LOCAL

on Microsoft Windows) as

follows:

setenv TNS_ADMIN /home/webuser/instantclient

Now, you can connect as follows:

url = "jdbc:oracle:oci:@conn_str"

Note:

The

TNS_ADMIN

environment variable specifies the directory where the

tnsnames.ora

file is located. However,

TNS_ADMIN

does not specify the full

path of the

tnsnames.ora

file, instead it specifies the directory.

If this

tnsnames.ora

file is located in the

/network/server6/home/dba/oracle/

network/admin

directory in the Oracle home, then instead of using

TNS_ADMIN

to locate

the

tnsnames.ora

file, you can set the

ORACLE_HOME

environment variable as follows:

setenv ORACLE_HOME /network/server6/home/dba/oracle

Now, you can connect with either of the

conn_str

connection strings, as specified

previously.

tnsnames.ora

can be located by

TNS_ADMIN

ORACLE_HOME

, then

TWO_TASK

can be

set to:

setenv TWO_TASK conn_str

You can then connect with the following URL:

url = "jdbc:oracle:oci:@"

Chapter 6

OCI Instant Client

6-8

6.4.9 Environment Variables for OCI Instant Client

The

ORACLE_HOME

environment variable no longer determines the location of the NLS, CORE,

and error message files. An OCI-only application does not require the

ORACLE_HOME

environment variable to be set. However, if the variable is set, then it does not have an

impact on the operation of the OCI driver. OCI driver always obtains its data from the Data

Shared Library. If the Data Shared Library is not available, only then the

ORACLE_HOME

environment variable is used and a full client installation is assumed. Even though the

ORACLE_HOME

environment variable is not required to be set, if it is set, then it must be set to a

valid operating system path name that identifies a directory.

Environment variables

ORA_NLS10

and

ORA_NLSPROFILES33

are ignored while using the Instant

Client.

If the

ORA_TZFILE

variable is not set, then the Instant Client uses the larger

timezlrg_n.dat

file from the Data Shared Library, which is the default setting. If the smaller

timezone_n.dat

file is to be used from the Data Shared Library, then set the

ORA_TZFILE

environment variable

to the name of the file without any absolute or relative path names. That is:

On UNIX systems:

setenv ORA_TZFILE timezone_n.dat

On Microsoft Windows:

set ORA_TZFILE timezone_n.dat

In the examples above, n is the time zone data file version number.

If the OCI driver is not using the Instant Client because of nonavailability of the Data Shared

Library, then the

ORA_TZFILE

variable, if set, names a complete path name, as it does in

previous Oracle Database releases.

TNSNAMES

entries are used, then, as mentioned earlier, the

TNS_ADMIN

directory must

contain the

TNSNAMES

configuration files, and if

TNS_ADMIN

is not set, then the

ORACLE_HOME/

network/admin

directory must contain Oracle Net Services configuration files.

6.5 About Instant Client Light (English)

The lightweight version of Instant Client is called Instant Client Light (English). Instant Client

Light is the short name. Instant Client Light is a significantly smaller version of Instant Client.

This reduces the disk space requirements of the client installation by about 63 MB. This is

achieved by the lightweight Data Shared Library,

libociicus.so

on UNIX systems, which is 4

MB in size and a subset of the data shared library,

libociei.so

, which is 67 MB in size.

The lightweight data shared library supports only a few character sets and error messages

that are only in English. Therefore, the name Instant Client Light (English). Instant Client Light

is designed for applications that require English-only error messages and use either

US7ASCII, WE8DEC, or one of the Unicode character sets.

This section covers the following topics:

• Data Shared Library for Instant Client Light (English)

• Globalization Settings

• Operation

Chapter 6

About Instant Client Light (English)

6-9

• Installing Instant Client Light (English)

6.5.1 Data Shared Library for Instant Client Light (English)

This section lists the names of the data shared libraries for Instant Client and Instant

Client Light (English) on different platforms.

The following table specifies the size of each data shared library in parentheses

following the library file name.

Table 6-2 Data Shared Library for Instant Client and Instant Client Light

(English)

Platform Instant Client Instant Client Light (English)

Solaris

libociei.so

(67 MB)

libociicus.so

(4 MB)

Linux

libociei.so

(67 MB)

libociicus.so

(4 MB)

Microsoft Windows

oraociei21.dll

(85 MB)

oraociicus21.dll

(15 MB)

6.5.2 Globalization Settings

The

NLS_LANG

setting determines the language, territory, and character set as

language_territory.characterset

. In Instant Client Light,

language

can only be

American

territory

can be any that is supported, and

characterset

can be any one

of the following:

• Single-byte

– US7ASCII

– WE8DEC

– WE8MSWIN1252

– WE8ISO8859P1

• Unicode

– UTF8

– AL16UTF16

– AL32UTF8

Specifying character set or national character set other than those listed as the client

or server character set or setting the language in

NLS_LANG

on the client will throw one

of the following errors:

•

ORA-12734

•

ORA-12735

•

ORA-12736

•

ORA-12737

With Instant Client Light, the error messages obtained are only in English. Therefore,

the valid values for the

NLS_LANG

setting are of the type:

American_territory.characterset

Chapter 6

About Instant Client Light (English)

6-10

where,

territory

can be any valid and supported territory and

characterset

can be any one

the previously listed character sets.

Instant Client Light can operate with the OCI environment handles created in the OCI_UTF16

mode.

See Also:

Oracle Database Globalization Support Guide for more information about NLS

settings

6.5.3 Operation

To use the Instant Client Light, an application must set the

LD_LIBARARY_PATH

environment

variable in UNIX systems or the

PATH

environment variable in Microsoft Windows to a location

containing the client and data shared libraries. OCI applications by default look for the OCI

Data Shared Library,

libociei.so

in the

LD_LIBRARY_PATH

environment variable in UNIX

systems or the

oraociei18.dll

Data Shared Library in the

PATH

environment variable in

Microsoft Windows, to determine if the application should use the Instant Client. In case this

library is not found, then OCI tries to load the Instant Client Light Data Shared Library,

libociicus.so

in UNIX systems or

libociicus18.dll

in Microsoft Windows. If this library is

found, then the application uses the Instant Client Light. Otherwise, a non-Instant Client is

used.

6.5.4 Installing Instant Client Light (English)

This section describes the ways to install Instant Client Light.

Instant Client Light can be installed in one of the following ways:

• From OTN

You can download the required file from

https://www.oracle.com/in/database/technologies/instant-client.html

For Instant Client Light, instead of downloading and expanding the Basic package,

download and unzip the Basic Light package. The directory in which the lightweight

libraries are unzipped should be empty before unzipping the files.

• From Client Admin Install

Instead of copying

libociei.so

oraociei21.dll

from the

ORACLE_HOME/

instantclient

directory, copy

libociicus.so

oraociic21.dll

from the

ORACLE_HOME/

instantclient/light

directory. That is, the Instant Client directory on the

LD_LIBRARY_PATH

environment variable, in UNIX systems, should contain the Instant

Client Light Data Shared Library,

libociicus.so

, instead of the larger OCI Instant Client

Data Shared Library,

libociei.so

. In Microsoft Windows, the

PATH

environment variable

should contain

oraociicus21.dll

instead of

oraociei21.dll

• From Oracle Universal Installer

If the Instant Client option is selected from Oracle Universal Installer, then

libociei.so

(or

oraociei21.dll

on Microsoft Windows) is installed in the base directory of the

installation which is going to be placed on the

LD_LIBRARY_PATH

environment variable.

Chapter 6

About Instant Client Light (English)

6-11

This is so that Instant Client Light is not enabled by default. The Instant Client

Light Data Shared Library,

libociicus.so

(or

oraociicus21.dll

on Microsoft

Windows), is installed in the

light

subdirectory of the base directory. Therefore, to

use in the Instant Client Light, the OCI Data Shared Library,

libociei.so

(or

oraociei21.dll

on Windows) must be deleted or renamed and the Instant Client

Light Data Shared Library must be copied from the

light

subdirectory to the base

directory of the installation.

For example, if Oracle Universal Installer has installed the Instant Client in

my_oraic_21_1

directory on the

LD_LIBRARY_PATH

environment variable, then you

must perform the following to use the Instant Client Light:

cd my_oraic_21_1

rm libociei.so

mv light/libociicus.so .

Note:

All the Instant Client files should always be copied or installed in an

empty directory. This is to ensure that no incompatible binaries exist in

the installation.

Chapter 6

About Instant Client Light (English)

6-12

Server-Side Internal Driver

This chapter covers the following topics:

• Overview of the Server-Side Internal Driver

• Connecting to the Database

• About Session and Transaction Context

• Testing JDBC on the Server

• Loading an Application into the Server

7.1 Overview of the Server-Side Internal Driver

The server-side internal driver is intrinsically tied to Oracle Database and to the embedded

Java Virtual Machine, also known as Oracle Java Virtual Machine (Oracle JVM). The driver

runs as part of the same process as the Database. It also runs within the default session, the

same session in which the Oracle JVM was started. Each Oracle JVM session has a single

implicit native connection to the Database session in which it exists. This connection is

conceptual and is not a Java object. It is an inherent aspect of the session and cannot be

opened or closed from within the JVM.

The server-side internal driver is optimized to run within the database server and provide

direct access to SQL data and PL/SQL subprograms on the local database. The entire JVM

operates in the same address space as the database and the SQL engine. Access to the

SQL engine is a function call. This enhances the performance of your Java Database

Connectivity (JDBC) applications and is much faster than running a remote Oracle Net call to

access the SQL engine.

The server-side internal driver supports the same features, application programming

interfaces (APIs), and Oracle extensions as the client-side drivers. This makes application

partitioning very straightforward. For example, if you have a Java application that is data-

intensive, then you can easily move it into the database server for better performance,

without having to modify the application-specific calls.

7.2 Connecting to the Database

As described in the preceding section, the server-side internal driver runs within a default

session. Therefore, you are already connected. There are two methods to access the default

connection:

• Use the

OracleDataSource.getConnection

method, with any of the following forms as

the URL string:

–

jdbc:oracle:kprb

–

jdbc:default:connection

–

jdbc:oracle:kprb:

–

jdbc:default:connection:

7-1

• Use the Oracle-specific

defaultConnection

method of the

OracleDriver

class.

Using

defaultConnection

is generally recommended.

Note:

You are no longer required to register the

OracleDriver

class for connecting

with the server-side internal driver.

Connecting with the OracleDriver Class defaultConnection Method

The

defaultConnection

method of the

oracle.jdbc.OracleDriver

class is an Oracle

extension and always returns the same connection object. Even if you call this method

multiple times, assigning the resulting connection object to different variable names,

then only a single connection object is reused.

You need not include a connection string in the

defaultConnection

call. For example:

import java.sql.*;

import oracle.jdbc.*;

class JDBCConnection

{

public static Connection connect() throws SQLException

{

Connection conn = null;

try {

// connect with the server-side internal driver

conn = ora.defaultConnection();

}

} catch (SQLException e) {...}

return conn;

}

Note that there is no

conn.close

call in the example. When JDBC code is running

inside the target server, the connection is an implicit data channel, not an explicit

connection instance as from a client. It should not be closed.

OracleDriver has a static variable to store a default connection instance. The method

OracleDriver.defaultConnection

returns this default connection instance if the

connection exists and is not closed. Otherwise, it creates a new, open instance and

stores it in the static variable and returns it to the caller.

Typically, you should use the

OracleDriver.defaultConnection

method. This method

is faster and uses less resources. Java stored procedures should be carefully written.

For example, to close statements before the end of each call.

Typically, you should not close the default connection instance because it is a single

instance that can be stored in multiple places, and if you close the instance, each

would become unusable. If it is closed, a later call to the

OracleDriver.defaultConnection

method gets a new, open instance.

Chapter 7

Connecting to the Database

7-2

Connecting with the OracleDataSource.getConnection Method

To connect to the internal server connection from code that is running within the target server,

you can use the

OracleDataSource.getConnection

method with either of the following URLs:

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:kprb");

Connection conn = ods.getConnection();

or:

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:default:connection");

Connection conn = ods.getConnection();

Any user name or password you include in the URL is ignored in connecting to the default

server connection.

The

OracleDataSource.getConnection

method returns a new Java

Connection

object every

time you call it. The fact that

OracleDataSource.getConnection

returns a new connection

object every time you call it is significant if you are working with object maps or type maps. A

type map is associated with a specific

Connection

object and with any state that is part of the

object. If you want to use multiple type maps as part of your program, then you can call

getConnection

to create a new

Connection

object for each type map.

Note:

Although the

OracleDataSource.getConnection

method returns a new object every

time you call it, it does not create a new database connection every time. They all

utilize the same implicit native connection and share the same session state, in

particular, the local transaction.

7.3 About Session and Transaction Context

The server-side driver operates within a default session and default transaction context. The

default session is the session in which the JVM was started. In effect, you are already

connected to the database on the server. This is different from the client-side where there is

no default session. You must explicitly connect to the database.

Auto-commit mode is disabled in the server. You must manage transaction

COMMIT

and

ROLLBACK

operations explicitly by using the appropriate methods on the connection object:

conn.commit();

or:

conn.rollback();

Chapter 7

About Session and Transaction Context

7-3

Note:

As a best practice, it is recommended not to commit or rollback a transaction

inside the server.

7.4 Testing JDBC on the Server

Almost any JDBC program that can run on a client can also run on the server. All the

programs in the

samples

directory can be run on the server, with only minor

modifications. Usually, these modifications concern only the connection statement.

Consider the following code fragment which obtains a connection to a database:

ods.setUrl(

"jdbc:oracle:oci:@(DESCRIPTION=

(ADDRESS=(PROTOCOL=TCP)(HOST=cluster_alias)

(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=orcl)))");

ods.setUser("HR");

ods.setPassword("hr");

Connection conn = ods.getConnection();

We can modify this code fragment for use in the server-side internal driver. In the

server-side internal driver, no user, password, or database information is necessary.

For the connection statement, you use:

ods.setUrl(

"jdbc:oracle:kprb:@");

Connection conn = ods.getConnection();

However, the most convenient way to get a connection is to call the

OracleDriver.defaultConnection

method, as follows:

Connection conn = OracleDriver.defaultConnection();

7.5 Loading an Application into the Server

When loading an application into the server, you can load

.class

files that you have

already compiled on the client or you can load

.java

source files and have them

automatically compiled on the server.

7.5.1 Using the Loadjava Utility

You can use the

loadjava

utility to load your files. You can either specify source file

names on the command line or put the files into a Java Archive (JAR) file and specify

the JAR file name on the command line.

The

loadjava

script, which runs the actual utility, is in the

bin

directory in your Oracle

home. This directory should already be in your path once Oracle has been installed.

Chapter 7

Testing JDBC on the Server

7-4

Note:

The

loadjava

utility supports compressed files.

Loading Class Files into the Server

Consider a case where you have the following three class files in your application:

Foo1.class

Foo2.class

, and

Foo3.class

. Each class is written into its own class schema

object in the server.

You can load the class files using the default JDBC Oracle Call Interface (OCI) driver in the

following ways:

• Specifying the individual class file names, as follows:

loadjava -user HR Foo1.class Foo2.class Foo3.class

Password: password

• Specifying the class file names using a wildcard, as follows:

loadjava -user HR Foo*.class

Password: password

• Specifying a JAR file that contains the class files, as follows:

loadjava -user HR Foo.jar

Password: password

You can load the files using the JDBC Thin driver, as follows:

loadjava -thin -user HR@localhost:5221:orcl Foo.jar

Password: password

Note:

Starting from Oracle Database 12c Release 1 (12.1), JDK 6, and JDK 7 are

supported. However, only one of the JVMs will be active at a given time.

Ensure that your classes are not compiled using a newer version of JDK than the

active runtime version on the server.

Loading Source Files into the Server

If you enable the

loadjava -resolve

option when loading a

.java

source file, then the

server-side compiler will compile your application as it is loaded, resulting in both a source

schema object for the original source code and one or more class schema objects for the

compiled output.

If you do not specify

-resolve

, then the source is loaded into a source schema object without

any compilation. In this case, however, the source is implicitly compiled the first time an

attempt is made to use a class defined in the source.

For example, run

loadjava

as follows to load and compile

Foo.java

, using the default JDBC

OCI driver:

Chapter 7

Loading an Application into the Server

7-5

loadjava -user HR -resolve Foo.java

Password: password

Or, use the following command to load using the JDBC Thin driver:

loadjava -thin -user HR@localhost:5221:orcl -resolve Foo.java

Password: password

Either of these will result in appropriate class schema objects being created in addition

to the source schema object.

Note:

Oracle generally recommends compiling source on the client, whenever

possible, and loading the

.class

files instead of the source files into the

server.

See Also:

Oracle Database Java Developer's Guide

7.5.2 Using the JVM Command Line

You can also use the JVM command-line option to load your files. The command-line

interface to Oracle JVM is analogous to using the JDK or JRE shell commands. You

can:

• Use the standard

-classpath

syntax to indicate where to find the classes to load

• Set the system properties by using the standard

-D

syntax

The interface is a PL/SQL function that takes a string (

VARCHAR2

) argument, parses it

as a command-line input and if it is properly formed, runs the indicated Java method in

Oracle JVM. To do this, PL/SQL package

DBMS_JAVA

provides the following functions:

•

runjava

You can use the

runjava

function in the following way:

FUNCTION runjava(cmdline VARCHAR2) RETURN VARCHAR2;

•

runjava_in_current_session

You can use the

runjava_in_current_session

function in the following way:

FUNCTION runjava_in_current_session(cmdline VARCHAR2) RETURN VARCHAR2;

Chapter 7

Loading an Application into the Server

7-6

Note:

Starting with Oracle Database 11g Release 1, there is a just-in-time (JIT) compiler

for Oracle JVM environment. A JIT compiler for Oracle JVM enables much faster

execution because the JIT compiler uses advanced techniques as compared to the

old Native compiler and compiles dynamically generated code. Unlike the old Native

compiler, the JIT compiler does not require a C compiler. It is enabled without the

support of any plug-ins.

Chapter 7

Loading an Application into the Server

7-7

Part III

Connection and Security

This part consists of chapters that discuss the use of data sources and URLs to connect to

the database. It also includes chapters that discuss the security features supported by the

Oracle Java Database Connectivity (JDBC) Oracle Call Interface (OCI) and Thin drivers,

Secure Sockets Layer (SSL) support in JDBC Thin driver, and middle-tier authentication

through proxy connections.

Part III contains the following chapters:

• Data Sources and URLs

• JDBC Client-Side Security Features

• Proxy Authentication

Data Sources and URLs

This chapter discusses connecting applications to databases using Java Database

Connectivity (JDBC) data sources, as well as the URLs that describe databases. This chapter

contains the following sections:

• About Data Sources

• Database URLs and Database Specifiers

8.1 About Data Sources

Data sources are standard, general-use objects for specifying databases or other resources

to use. The JDBC 2.0 extension application programming interface (API) introduced the

concept of data sources. For convenience and portability, data sources can be bound to Java

Naming and Directory Interface (JNDI) entities, so that you can access databases by logical

names.

The data source facility provides a complete replacement for the previous JDBC

DriverManager

facility. You can use both facilities in the same application, but it is

recommended that you transition your application to data sources.

This section covers the following topics:

• Overview of Oracle Data Source Support for JNDI

• Features and Properties of Data Sources

• Creating a Data Source Instance and Connecting

• Creating a Data Source Instance_ Registering with JNDI_ and Connecting

• Supported Connection Properties

• About Using Roles for SYS Login

• Configuring Database Remote Login

• Using Bequeath Connection and SYS Logon

• Setting Properties for Oracle Performance Extensions

• Support for Network Data Compression

8.1.1 Overview of Oracle Data Source Support for JNDI

The JNDI standard provides a way for applications to find and access remote services and

resources. These services can be any enterprise services. However, for a JDBC application,

these services would include database connections and services.

JNDI enables an application to use logical names in accessing these services, removing

vendor-specific syntax from application code. JNDI has the functionality to associate a logical

name with a particular source for a desired service.

8-1

All Oracle JDBC data sources are JNDI-referenceable. The developer is not required

to use this functionality, but accessing databases through JNDI logical names makes

the code more portable.

Note:

Using JNDI functionality requires the

jndi.jar

file to be in the

CLASSPATH

environment variable. This file is included with the Java products on the

installation CD. You must add it to the

CLASSPATH

environment variable

separately.

8.1.2 Features and Properties of Data Sources

By using the data source functionality with JNDI, you do not need to register the

vendor-specific JDBC driver class name and you can use logical names for URLs and

other properties. This ensures that the code for opening database connections is

portable to other environments.

The DataSource Interface and Oracle Implementation

A JDBC data source is an instance of a class that implements the standard

javax.sql.DataSource

interface:

public interface DataSource

{

Connection getConnection() throws SQLException;

Connection getConnection(String username, String password)

throws SQLException;

...

}

Oracle implements this interface with the

OracleDataSource

class in the

oracle.jdbc.pool

package. The overloaded

getConnection

method returns a

connection to the database.

To use other values, you can set properties using appropriate setter methods. For

alternative user names and passwords, you can also use the

getConnection

method

that takes these parameters as input. This would take priority over the property

settings.

Note:

The

OracleDataSource

class and all subclasses implement the

java.io.Serializable

and

javax.naming.Referenceable

interfaces.

Properties of DataSource

The

OracleDataSource

class, as with any class that implements the

DataSource

interface, provides a set of properties that can be used to specify a database to

connect to. These properties follow the JavaBeans design pattern.

Chapter 8

About Data Sources

8-2

The following tables list the

OracleDataSource

standard properties and Oracle extensions

respectively.

Note:

Oracle does not implement the standard

roleName

property.

Table 8-1 Standard Data Source Properties

Name Type Description

databaseName String

Name of the particular database on the server.

dataSourceName String

Name of the underlying data source class. For connection

pooling, this is an underlying pooled connection data source

class. For distributed transactions, this is an underlying XA

data source class.

description String

Description of the data source.

networkProtocol String

Network protocol for communicating with the server. For

Oracle, this applies only to the JDBC Oracle Call Interface

(OCI) drivers and defaults to

tcp

password String

Password for the connecting user.

portNumber int

Number of the port where the server listens for requests

serverName String

Name of the database server

user String

Name for the login

Note:

For security reasons, there is no

getPassword()

method.

Table 8-2 Oracle Extended Data Source Properties

Name Type Description

connectionCacheName String

Specifies the name of the cache. This cannot be

changed after the cache has been created.

connectionCacheProperties java.util.P

roperties

Specifies properties for implicit connection

cache.

connectionCachingEnabled Boolean

Specifies whether implicit connection cache is in

use.

connectionProperties java.util.P

roperties

Specifies the connection properties.

driverType String

Specifies Oracle JDBC driver type. It can be one

oci

thin

, or

kprb

fastConnectionFailoverEnable

Boolean

Specifies whether Fast Connection Failover is in

use.

Chapter 8

About Data Sources

8-3

Table 8-2 (Cont.) Oracle Extended Data Source Properties

Name Type Description

implicitCachingEnabled Boolean

Specifies whether the implicit statement

connection cache is enabled.

loginTimeout int

Specifies the maximum time in seconds that this

data source will wait while attempting to connect

to a database.

logWriter java.io.Pri

ntWriter

Specifies the log writer for this data source.

maxStatements int

Specifies the maximum number of statements in

the application cache.

serviceName String

Specifies the database service name for this

data source.

tnsEntry String

Specifies the TNS entry name. The TNS entry

name corresponds to the TNS entry specified in

the

tnsnames.ora

configuration file.

Enable this

OracleXADataSource

property

when using the Native XA feature with the OCI

driver, to access Oracle pre-8.1.6 databases and

later. If the

tnsEntry

property is not set when

using the Native XA feature, then a

SQLException

with error code ORA-17207 is

thrown

url String

Specifies the URL of the database connection

string. Provided as a convenience, it can help

you migrate from an older Oracle Database. You

can use this property in place of the Oracle

tnsEntry

and

driverType

properties and the

standard

portNumber

networkProtocol

serverName

, and

databaseName

properties.

nativeXA Boolean

Allows an

OracleXADataSource

using the

Native XA feature with the OCI driver, to access

Oracle pre-8.1.6 databases and later. If the

nativeXA

property is enabled, be sure to set

the

tnsEntry

property as well. This property is

only for

OracleXADatasource

This

DataSource

property defaults to

false

ONSConfiguration String

Specifies the ONS configuration string that is

used to remotely subscribe to FAN/ONS events.

Note:

• This table omits properties that supported the deprecated connection

cache based on

OracleConnectionCache

• Because Native XA performs better than Java XA, use Native XA

whenever possible.

Chapter 8

About Data Sources

8-4

Use the

setConnectionProperties

method to set the properties of the connection and the

setConnectionCacheProperties

method to set the properties of the connection cache.

If you are using the server-side internal driver, that is, the

driverType

property is set to

kprb

then any other property settings are ignored.

If you are using the JDBC Thin or OCI driver, then note the following:

• A URL setting can include settings for

user

and

password

, as in the following example, in

which case this takes precedence over individual

user

and

password

property settings:

jdbc:oracle:thin:HR/hr@localhost:5221:orcl

• Settings for

user

and

password

are required, either directly through the URL setting or

through the

getConnection

call. The

user

and

password

settings in a

getConnection

call

take precedence over any property settings.

• If the

url

property is set, then any

tnsEntry

driverType

portNumber

networkProtocol

serverName

, and

databaseName

property settings are ignored.

• If the

tnsEntry

property is set, which presumes the

url

property is not set, then any

databaseName

serverName

portNumber

, and

networkProtocol

settings are ignored.

• If you are using an OCI driver, which presumes the

driverType

property is set to

oci

and the

networkProtocol

is set to

ipc

, then any other property settings are ignored.

Also, note that

getConnectionCacheName()

will return the name of the cache only if the

ConnectionCacheName

property of the data source is set after caching is enabled on the data

source.

8.1.3 Creating a Data Source Instance and Connecting

This section shows an example of the most basic use of a data source to connect to a

database, without using JNDI functionality. Note that this requires vendor-specific, hard-

coded property settings.

Create an

OracleDataSource

instance, initialize its connection properties as appropriate, and

get a connection instance, as in the following example:

OracleDataSource ods = new OracleDataSource();

ods.setDriverType("oci");

ods.setServerName("localhost");

ods.setNetworkProtocol("tcp");

ods.setDatabaseName(<database_name>);

ods.setPortNumber(5221);

ods.setUser("HR");

ods.setPassword("hr");

Connection conn = ods.getConnection();

Or, optionally, override the user name and password, as follows:

Connection conn = ods.getConnection("OE", "oe");

8.1.4 Creating a Data Source Instance, Registering with JNDI, and

Connecting

This section exhibits JNDI functionality in using data sources to connect to a database.

Vendor-specific, hard-coded property settings are required only in the portion of code that

Chapter 8

About Data Sources

8-5

binds a data source instance to a JNDI logical name. From that point onward, you can

create portable code by using the logical name in creating data sources from which

you will get your connection instances.

Note:

Creating and registering data sources is typically handled by a JNDI

administrator, not in a JDBC application.

Initialize Data Source Properties

Create an

OracleDataSource

instance, and then initialize its properties as appropriate,

as in the following example:

OracleDataSource ods = new OracleDataSource();

ods.setDriverType("oci");

ods.setServerName("localhost");

ods.setNetworkProtocol("tcp");

ods.setDatabaseName("816");

ods.setPortNumber(5221);

ods.setUser("HR");

ods.setPassword("hr");

Once you have initialized the connection properties of the

OracleDataSource

instance

ods

, as shown in the preceding example, you can register this data source instance

with JNDI, as in the following example:

Context ctx = new InitialContext();

ctx.bind("jdbc/sampledb", ods);

Calling the JNDI

InitialContext()

constructor creates a Java object that references

the initial JNDI naming context. System properties, which are not shown, instruct JNDI

which service provider to use.

The

ctx.bind

call binds the

OracleDataSource

instance to a logical JNDI name. This

means that anytime after the

ctx.bind

call, you can use the logical name

jdbc/

sampledb

in opening a connection to the database described by the properties of the

OracleDataSource

instance

ods

. The logical name

jdbc/sampledb

is logically bound to

this database.

The JNDI namespace has a hierarchy similar to that of a file system. In this example,

the JNDI name specifies the subcontext

jdbc

under the root naming context and

specifies the logical name

sampledb

within the

jdbc

subcontext.

The

Context

interface and

InitialContext

class are in the standard

javax.naming

package.

Chapter 8

About Data Sources

8-6

Note:

The JDBC 2.0 Specification requires that all JDBC data sources be registered in the

jdbc

naming subcontext of a JNDI namespace or in a child subcontext of the

jdbc

subcontext.

Open a Connection

To perform a lookup and open a connection to the database logically bound to the JNDI

name, use the logical JNDI name. Doing this requires casting the lookup result, which is

otherwise a Java

Object

, to

OracleDataSource

and then using its

getConnection

method to

open the connection.

Here is an example:

OracleDataSource odsconn = (OracleDataSource)ctx.lookup("jdbc/sampledb");

Connection conn = odsconn.getConnection();

8.1.5 Supported Connection Properties

For a detailed list of connection properties that Oracle JDBC drivers support, see the Oracle

Database JDBC Java API Reference.

8.1.6 About Using Roles for SYS Login

To specify the role for the

SYS

internal_logon

connection property. To log on

SYS

, set the

internal_logon

connection property to

SYSDBA

SYSOPER

Note:

The ability to specify a role is supported only for the

sys

user name.

For a bequeath connection, we can get a connection as

SYS

by setting the

internal_logon

property. For a remote connection, we need additional password file setting procedures.

8.1.7 Configuring Database Remote Login

Before the JDBC Thin driver can connect to the database as

SYSDBA

, you must configure the

user, because Oracle Database security system requires a password file for remote

connections as an administrator. Perform the following:

1. Set a password file on the server-side or on the remote database, using the

orapwd

password utility. You can add a password file for user

SYS

as follows:

• In UNIX

orapwd file=$ORACLE_HOME/dbs/orapwORACLE_SID entries=200

Enter password: password

• In Microsoft Windows

Chapter 8

About Data Sources

8-7

orapwd file=%ORACLE_HOME%\database\PWDORACLE_SID.ora entries=200

Enter password: password

In this case,

file

is the name of the password file,

password

is the password for

user

SYS

. It can be altered using the

ALTER USER

statement in SQL Plus. You

should set

entries

to a value higher than the number of entries you expect.

The syntax for the password file name is different on Microsoft Windows and

UNIX.

See Also:

Oracle Database Administrator’s Guide

2. Enable remote login as

SYSDBA

. This step grants

SYSDBA

and

SYSOPER

system

privileges to individual users and lets them connect as themselves.

Stop the database, and add the following line to

initservice_name.ora

, in UNIX,

init.ora

, in Microsoft Windows:

remote_login_passwordfile=exclusive

The

initservice_name.ora

file is located at

ORACLE_HOME/dbs/

and also at

ORACLE_HOME/admin/db_name/pfile/

. Ensure that you keep the two files

synchronized.

The

init.ora

file is located at

%ORACLE_BASE%\ADMIN\db_name\pfile\

3. Change the password for the

SYS

user. This is an optional step.

PASSWORD sys

Changing password for sys

New password: password

Retype new password: password

4. Verify whether

SYS

has the

SYSDBA

privilege.

SQL> select * from v$pwfile_users;

USERNAME SYSDB SYSOP

---------------------- --------- ---------

SYS TRUE TRUE

5. Restart the remote database.

Example 8-1 Using SYS Login To Make a Remote Connection

//This example works regardless of language settings of the database.

/** case of remote connection using sys **/

import java.sql.*;

import oracle.jdbc.*;

import oracle.jdbc.pool.*;

// create an OracleDataSource

OracleDataSource ods = new OracleDataSource();

// set connection properties

java.util.Properties prop = new java.util.Properties();

prop.put("user", "sys");

prop.put("password", "sys");

prop.put("internal_logon", "sysoper");

ods.setConnectionProperties(prop);

// set the url

// the url can use oci driver as well as:

Chapter 8

About Data Sources

8-8

// url = "jdbc:oracle:oci8:@remotehost"; the remotehost is a remote database

String url = "jdbc:oracle:thin:@//localhost:5221/orcl";

ods.setURL(url);

// get the connection

Connection conn = ods.getConnection();

...

8.1.8 Using Bequeath Connection and SYS Logon

The following example illustrates how to use the

internal_logon

and

SYSDBA

arguments to

specify the

SYS

settings of the database.

/** Example of bequeath connection **/

import java.sql.*;

import oracle.jdbc.*;

import oracle.jdbc.pool.*;

// create an OracleDataSource instance

OracleDataSource ods = new OracleDataSource();

// set neccessary properties

java.util.Properties prop = new java.util.Properties();

prop.put("user", "sys");

prop.put("password", "sys");

prop.put("internal_logon", "sysdba");

ods.setConnectionProperties(prop);

// the url for bequeath connection

String url = "jdbc:oracle:oci8:@";

ods.setURL(url);

// retrieve the connection

Connection conn = ods.getConnection();

...

8.1.9 Setting Properties for Oracle Performance Extensions

Some of the connection properties are for use with Oracle performance extensions. Setting

these properties is equivalent to using corresponding methods on the

OracleConnection

object, as follows:

• Setting the

defaultRowPrefetch

property is equivalent to calling

setDefaultRowPrefetch

• Setting the

remarksReporting

property is equivalent to calling

setRemarksReporting

See Also:

"About Reporting DatabaseMetaData TABLE_REMARKS"

Example

The following example shows how to use the

put

method of the

java.util.Properties

class, in this case, to set Oracle performance extension parameters.

Chapter 8

About Data Sources

8-9

//import packages and register the driver

import java.sql.*;

import java.math.*;

import oracle.jdbc.*;

import oracle.jdbc.pool.OracleDataSource;

//specify the properties object

java.util.Properties info = new java.util.Properties();

info.put ("user", "HR");

info.put ("password", "hr");

info.put ("defaultRowPrefetch","20");

info.put ("defaultBatchValue", "5");

//specify the datasource object

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:thin:@//localhost:5221/orcl");

ods.setUser("HR");

ods.setPassword("hr");

ods.setConnectionProperties(info);

...

8.1.10 Support for Network Data Compression

Starting from Oracle Database 12c Release 2 (12.2.0.1), the JDBC Thin driver

supports network data compression. Network data compression reduces the size of

the session data unit (SDU) transmitted over a data connection and reduces the time

required to transmit a SQL query and the result across the network. The benefits are

more significant in case of Wireless Area Network (WAN). For enabling network data

compression, you must set the connection properties in the following way:

Note:

Network compression does not work for streamed data.

...

OracleDataSource ds = new OracleDataSource();

Properties prop = new Properties();

prop.setProperty("user","user1");

prop.setProperty("password",<password>);

// Enabling Network Compression

prop.setProperty("oracle.net.networkCompression","on");

//Optional configuration for setting the client compression threshold.

prop.setProperty("oracle.net.networkCompressionThreshold","1024");

ds.setConnectionProperties(prop);

ds.setURL(url);

Connection conn = ds.getConnection();

...

Chapter 8

About Data Sources

8-10

8.2 Database URLs and Database Specifiers

Database URLs are strings. The complete URL syntax is:

jdbc:oracle:driver_type:[username/password]@database_specifier

Note:

• The brackets indicate that the

username/password

pair is optional.

•

kprb

, the internal server-side driver, uses an implicit connection. Database

URLs for the server-side driver end after the

driver_type

The first part of the URL specifies which JDBC driver is to be used. The supported

driver_type

values are

thin

oci

, and

kprb

The remainder of the URL contains an optional user name and password separated by a

slash, an @, and the database specifier, which uniquely identifies the database to which the

application is connected. Some database specifiers are valid only for the JDBC Thin driver,

some only for the JDBC OCI driver, and some for both.

8.2.1 Support for Internet Protocol Version 6

This release of Oracle JDBC drivers supports Internet Protocol Version 6 (IPv6) addresses in

the JDBC URL and machine names that resolve to IPv6 addresses. IPv6 is a new Network

layer protocol designed by the Internet Engineering Task Force (IETF) to replace the current

version of Internet Protocol, Internet Protocol Version 4 (IPv4). The primary benefit of IPv6 is

a large address space, derived from the use of 128-bit addresses. IPv6 also improves upon

IPv4 in areas such as routing, network auto configuration, security, quality of service, and so

on.

Note:

• An IPv6 Client can support only IPv6 Servers or servers with dual protocol

support, that is, support for both IPv6 and IPv4 protocols. Conversely, an IPv6

Server can support only IPv6 clients or dual protocol clients.

• IPv6 is supported only with single instance Database servers and not with

Oracle RAC.

If you want to use a literal IPv6 address in a URL, then you should enclose the literal address

enclosed in a left bracket (

[

) and a right bracket (

]

). For example:

[2001:0db8:7654:3210:FEDC:BA98:7654:3210]

. So, a JDBC URL, using an IPv6 address will

look like the following:

jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)

(HOST=[2001:0db8:7654:3210:FEDC:BA98:7654:3210])(PORT=5521))

(CONNECT_DATA=(SERVICE_NAME=sales.example.com))

Chapter 8

Database URLs and Database Specifiers

8-11

Note:

All the new System classes that are required for IPv6 support are loaded

when Java is enabled during database initialization. So, if your application

does not have any IPv6 addressing, then you do not need to change your

code to use IPv6 functionality. However, if your application has either IPv6

only or both IPv6 and IPv4 addressing, then you should set the

java.net.preferIPv6Addresses

system property in the command line. This

enables the Oracle JVM to load appropriate libraries. These libraries are

loaded once and cannot be reloaded without restarting the Java process.

8.2.2 Support for HTTPS Proxy Configuration

Oracle Database Release 18c JDBC drivers support HTTPS Proxy Configuration.

HTTPS Proxy enables tunnelling secure connections over forward HTTP proxy using

the

HTTP CONNECT

method. This helps in accessing the public cloud database service

as it eliminates the requirement to open an outbound port on a client side firewall. This

parameter is applicable only to the connect descriptors where

PROTOCOL=TCPS

. This is

similar to the web browser setting for intranet users who want to connect to internet

hosts.

For configuring HTTPS Proxy, add details to the

ADDRESS

part of the Connection String

as shown in the following code snippet:

(DESCRIPTION=

(ADDRESS=(HTTPS_PROXY=sales-proxy)(HTTPS_PROXY_PORT=8080)

(PROTOCOL=TCPS)(HOST=sales2-svr)(PORT=443))

(CONNECT_DATA=(SERVICE_NAME=sales.us.example.com)))

8.2.3 Database Specifiers

Table 8-3, shows the possible database specifiers, listing which JDBC drivers support

each specifier.

Note:

• Starting Oracle Database 10g, Oracle Service IDs are not supported.

• Starting Oracle Database 10g, Oracle no longer supports Oracle Names

as a naming method.

Chapter 8

Database URLs and Database Specifiers

8-12

Table 8-3 Supported Database Specifiers

Specifier Supported

Drivers

Example

Oracle Net

connection

descriptor

Thin, OCI Thin, using an address list:

url="jdbc:oracle:thin:@(DESCRIPTION=

(LOAD_BALANCE=on)

(ADDRESS_LIST=

(ADDRESS=(PROTOCOL=TCP)(HOST=host1) (PORT=5221))

(ADDRESS=(PROTOCOL=TCP)(HOST=host2)(PORT=5221)))

(CONNECT_DATA=(SERVICE_NAME=orcl)))"

OCI, using a cluster:

"jdbc:oracle:oci:@(DESCRIPTION=

(ADDRESS=(PROTOCOL=TCP)(HOST=cluster_alias)

(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=orcl)))"

Thin-style service

name

Thin Refer to "Thin-style Service Name Syntax" for details.

"jdbc:oracle:thin:HR/hr@//localhost:5221/orcl"

LDAP syntax Thin Refer to LDAP Syntax for details.

"jdbc:oracle:thin:@ldap://ldap.example.com:7777/

sales,cn=OracleContext,dc=com"

Bequeath

connection

OCI Empty. That is, nothing after @

"jdbc:oracle:oci:HR/hr/@"

TNSNames alias Thin, OCI Refer to "TNSNames Alias Syntax" for details.

OracleDataSource ods = new OracleDataSource();

ods.setTNSEntryName("MyTNSAlias");

8.2.4 Thin-style Service Name Syntax

Thin-style service names are supported only by the JDBC Thin driver. The syntax is:

@//host_name:port_number/service_name

For example:

jdbc:oracle:thin:HR/hr@//localhost:5221/orcl

Note:

The JDBC Thin driver supports only the TCP/IP protocol.

Chapter 8

Database URLs and Database Specifiers

8-13

8.2.5 Support for Easy Connect Plus

Oracle Database Release 19c JDBC driver introduced enhancements to the

EasyConnect URL with many capabilities and this new enhanced Easy Connection

URL is called Easy Connect Plus.

The EasyConnect URL supported simplified connection strings and the TCP transfer

protocol. The goal of the enhancement to the EasyConnect URL is to simplify the

client-side deployment and configuration, while connecting to the database. This

enhancement can eliminate the need of using the

tnsnames.ora

file and you do not

need to specify the

TNS_ADMIN

environment variable. The main features of Easy

Connect Plus are the following:

• Support for TCPS Protocol

• Support for Multiple Host and Port

• Support to Pass Connection Properties in the Connection String

8.2.5.1 Support for TCPS Protocol

The EasyConnect URL supported only the TCP transport protocol. However, the Easy

Connect Plus supports both TCP and TCPS protocols. This enhancement simplifies

the client configurations to Oracle Database Cloud Services that mandate TCPS

connections.

For example, if you have a EasyConnect URL in the following format:

jdbc:oracle:thin:@(DESCRIPTION=

(ADDRESS=(PROTOCOL=tcps)(HOST=salesserver1)(PORT=1521))

(CONNECT_DATA=(SERVICE_NAME=sales.us.example.com)))

Then, the Easy Connect Plus URL will be:

jdbc:oracle:thin:@tcps://salesserver1:1521/sales.us.example.com

8.2.5.2 Support for Multiple Host and Port

Using Easy Connect Plus, you can specify a comma-separated list of hosts.

The EasyConnect URL allowed only single host name and single port. But, Easy

Connect Plus allows specifying multiple hosts and multiple ports in the connection

string, which can be used to connect to a database with load balancing turned on.

For example, if you want to specify two hosts with a single port number in the

connection using the following EasyConnect URL:

jdbc:oracle:thin:@(DESCRIPTION=

(ADDRESS_LIST= (LOAD_BALANCE=ON) (ADDRESS=(PROTOCOL=tcp)

(HOST=salesserver1)(PORT=1521)) (ADDRESS=(PROTOCOL=tcp)

(HOST=salesserver2)(PORT=1521)))

(CONNECT_DATA=(SERVICE_NAME=sales.us.example.com)))

Chapter 8

Database URLs and Database Specifiers

8-14

Then, the Easy Connect Plus URL will be the following:

jdbc:oracle:thin:@tcp://salesserver1,salesserver2:1521/sales.us.example.com

Again, if you want to specify multiple hosts as a list, where each list follows its own port

number, using the following EasyConnect URL:

jdbc:oracle:thin:@(DESCRIPTION= (ADDRESS_LIST= (LOAD_BALANCE=ON)

(ADDRESS=(PROTOCOL=tcp)(HOST=salesserver1)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=salesserver2)(PORT=1522))

(ADDRESS=(PROTOCOL=tcp)(HOST=salesserver3)(PORT=1522)))

(CONNECT_DATA=(SERVICE_NAME=sales.us.example.com)))

Then, the Easy Connect Plus URL will be the following:

jdbc:oracle:thin:@tcp://salesserver1:1521,salesserver2,salesserver3:1522/

sales.us.example.com

8.2.5.3 Support to Pass Connection Properties in the Connection String

Easy Connect Plus supports specification of connection properties as name-value pairs in the

connection URL. After the

delimiter, Easy Connect Plus supports a list of parameters as

name-value pairs, which can be optionally specified.

Remember the following points while specifying the name-value pairs:

• Use a question mark sign (

) to indicate the start of the name-value pairs and an

ampersand sign (

) as a delimiter between each name-value pair.

• Specify the entire connection string as a single string.

• Use the backslash (

) escape character if there are any special characters in the value.

• Place white spaces within double-quotes if they are required as part of the value because

leading and trailing white spaces are ignored within the parameter values.

The following table lists a few of the supported parameters:

Parameter Name Old URL Example New URL Example

wallet_location jdbc:oracle:thin:@(DESCRI

PTION=

(ADDRESS=(PROTOCOL=tcps)

(HOST=salesserver1)

(PORT=1521))

(CONNECT_DATA=(SERVICE_NA

ME=sales.us.example.com))

jdbc:oracle:thin:@tcps://

salesserver1.com:1521/

sales.us.example.com?

wallet_location=/Users/

jsmith/DBCloudService/

wallet_JDBCTEST&oracle.ne

t.ssl_server_cert_dn=\"CN

=salesserver2.com.com,OU=

Oracle BMCS US,O=Oracle

Corporation,L=Redwood

City,ST=California,C=US\"

ssl_server_dn_match

Chapter 8

Database URLs and Database Specifiers

8-15

Parameter Name Old URL Example New URL Example

ssl_server_cert_dn jdbc:oracle:thin:@(DESCRI

PTION=

(ADDRESS=(PROTOCOL=tcps)

(HOST=salesserver1)

(PORT=1521)) (SECURITY=

(SSL_SERVER_DN_MATCH=TRUE

)

(SSL_SERVER_CERT_DN=cn=sa

les,cn=OracleContext,dc=u

s,dc=example,dc=com))

(CONNECT_DATA=(SERVICE_NA

ME=sales.us.example.com))

)

jdbc:oracle:thin:@tcps://

salesserver1:1521/

sales.us.example.com?

ssl_server_cert_dn="cn=sa

les,cn=OracleContext,dc=u

s,dc=example,dc=com"

https_proxy

and

https_proxy_port

jdbc:oracle:thin:@(DESCRI

PTION=

(ADDRESS=(PROTOCOL=tcps)

(HOST=salesserver1)

(PORT=1521)

(https_proxy=www-

proxy.mycompany.com)

(https_proxy_port=80))

(CONNECT_DATA=(SERVICE_NA

ME=sales.us.example.com))

)

jdbc:oracle:thin:@tcps://

salesserver1:1521/

sales.us.example.com?

https_proxy=www-

proxy.mycompany.com&https

_proxy_port=80

connect_timeout jdbc:oracle:thin:@(DESCRI

PTION= (retry_count=3)

(connect_timeout=60)

(transport_connect_timeou

t=30)

(ADDRESS=(PROTOCOL=tcp)

(HOST=salesserver1)

(PORT=1521))

(CONNECT_DATA=(SERVICE_NA

ME=sales.us.example.com))

)

jdbc:oracle:thin:@tcps://

salesserver1:1521/

sales.us.example.com?

connect_timeout=60&

transport_connect_timeout

=30&retry_count=3

The list of supported keywords under

DESCRIPTION

is as follows:

•

ENABLE

•

FAILOVER

•

LOAD_BALANCE

•

RECV_BUF_SIZE

•

SEND_BUF_SIZE

•

SDU

•

SOURCE_ROUTE

•

RETRY_COUNT

•

RETRY_DELAY

•

CONNECT_TIMEOUT

Chapter 8

Database URLs and Database Specifiers

8-16

•

TRANSPORT_CONNECT_TIMEOUT

8.2.6 Support for Delay in Connection Retries

Starting from Oracle Database 12c Release 1 (12.1.0.2), there is a new connection attribute

RETRY_DELAY

, which specifies the delay between connection retries in seconds. The following

code snippet shows how to use this attribute:

(DESCRIPTION_LIST=

(DESCRIPTION=

(CONNECT_TIMEOUT=10)(RETRY_COUNT=3)(RETRY_DELAY=3)

(ADDRESS_LIST=

(ADDRESS=(PROTOCOL=tcp)(HOST=myhost1)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=myhost2)(PORT=1521)))

(CONNECT_DATA=(SERVICE_NAME=example1.com)))

(DESCRIPTION=

(CONNECT_TIMEOUT=60)(RETRY_COUNT=1)(RETRY_DELAY=5)

(ADDRESS_LIST=

(ADDRESS=(PROTOCOL=tcp)(HOST=myhost3)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=myhost4)(PORT=1521)))

(CONNECT_DATA=(SERVICE_NAME=example2.com))))

8.2.7 TNSNames Alias Syntax

You can find the available

TNSNAMES

entries listed in the

tnsnames.ora

file on the client

computer from which you are connecting. On Windows, this file is located in the

ORACLE_HOME\NETWORK\ADMIN

directory. On UNIX systems, you can find it in the

ORACLE_HOME

directory or the directory indicated in your

TNS_ADMIN

environment variable.

For example, if you want to connect to the database on host

myhost

as user

with password

that has a

TNSNAMES

entry of

MyHostString

, then write the following:

OracleDataSource ods = new OracleDataSource();

ods.setTNSEntryName("MyTNSAlias");

ods.setUser("HR");

ods.setPassword("hr");

ods.setDriverType("oci");

Connection conn = ods.getConnection();

The

oracle.net.tns_admin

system property must be set to the location of the

tnsnames.ora

file so that the JDBC Thin driver can locate the

tnsnames.ora

file. For example:

System.setProperty("oracle.net.tns_admin", "c:\\Temp");

String url = "jdbc:oracle:thin:@tns_entry";

Note:

When using

TNSNames

with the JDBC Thin driver, you must set the

oracle.net.tns_admin

property to the directory that contains your

tnsnames.ora

file.

java -Doracle.net.tns_admin=$ORACLE_HOME/network/admin

Chapter 8

Database URLs and Database Specifiers

8-17

8.2.8 LDAP Syntax

An example of database specifier using the Lightweight Directory Access Protocol

(LDAP) syntax is as follows:

"jdbc:oracle:thin:@ldap://ldap.example.com:7777/sales,cn=OracleContext,dc=com"

When using SSL, change this to:

"jdbc:oracle:thin:@ldaps://ldap.example.com:7777/sales,cn=OracleContext,dc=com"

Note:

The JDBC Thin driver can use LDAP over SSL to communicate with Oracle

Internet Directory if you substitute

ldaps:

for

ldap:

in the database specifier.

The LDAP server must be configured to use SSL. If it is not, then the

connection attempt will hang.

The JDBC Thin driver supports failover of a list of LDAP servers during the service

name resolution process, without the need for a hardware load balancer. Also, client-

side load balancing is supported for connecting to LDAP servers. A list of space

separated LDAP URLs syntax is used to support failover and load balancing.

When a list of LDAP URLs is specified, both failover and load balancing are enabled

by default. The

oracle.net.ldap_loadbalance

connection property can be used to

disable load balancing, and the

oracle.net.ldap_failover

connection property can

be used to disable failover.

An example, which uses failover, but with client-side load balancing disabled, is as

follows:

Properties prop = new Properties();

String url = "jdbc:oracle:thin:@ldap://ldap1.example.com:3500/

cn=salesdept,cn=OracleContext,dc=com/salesdb " +

"ldap://ldap2.example.com:3500/cn=salesdept,cn=OracleContext,dc=com/salesdb " +

"ldap://ldap3.example.com:3500/cn=salesdept,cn=OracleContext,dc=com/salesdb";

prop.put("oracle.net.ldap_loadbalance", "OFF" );

OracleDataSource ods = new OracleDataSource();

ods.setURL(url);

ods.setConnectionProperties(prop);

The JDBC Thin driver supports LDAP nonanonymous bind. A set of JNDI environment

properties, which contains authentication information, can be specified for a data

source. If an LDAP server is configured as not to allow anonymous bind, then

authentication information must be provided to connect to the LDAP server. The

following example shows a simple clear-text password authentication:

String url = "jdbc:oracle:thin:@ldap://ldap.example.com:7777/

sales,cn=salesdept,cn=OracleContext,dc=com";

Properties prop = new Properties();

prop.put("java.naming.security.authentication", "simple");

prop.put("java.naming.security.principal","cn=salesdept,cn=OracleContext,dc=com")

;

Chapter 8

Database URLs and Database Specifiers

8-18

prop.put("java.naming.security.credentials", "mysecret");

OracleDataSource ods = new OracleDataSource();

ods.setURL(url);

ods.setConnectionProperties(prop);

Since JDBC passes down the three properties to JNDI, the authentication mechanism

chosen by client is consistent with how these properties are interpreted by JNDI. For

example, if the client specifies authentication information without explicitly specifying the

java.naming.security.authentication

property, then the default authentication mechanism

is "simple".

Chapter 8

Database URLs and Database Specifiers

8-19

JDBC Client-Side Security Features

This chapter discusses support for IAM authentication for Autonomous Database, login

authentication, network encryption and integrity with respect to features of the Oracle

Advanced Security options in the JDBC OCI and the JDBC Thin drivers.

Note:

• This discussion is not relevant to the server-side internal driver because all

communication through server-side internal driver is completely internal to the

server.

• Using

SHA-1

(Secure Hash Algorithm 1) with the parameters

SQLNET.CRYPTO_CHECKSUM_TYPES_CLIENT

and

SQLNET.CRYPTO_CHECKSUM_TYPES_SERVER

is deprecated in this release, and can

be desupported in a future release. Using

SHA-1

ciphers with

DBMS_CRYPTO

also deprecated (

HASH_SH1

HMAC_SH1

). Instead of using

SHA1

, Oracle

recommends that you start using a stronger

SHA-2

cipher in place of the

SHA-1

cipher.

Oracle Advanced Security, previously known as the Advanced Networking Option (ANO) or

Advanced Security Option (ASO), provides industry standards-based network encryption,

network integrity, third-party authentication, single sign-on, and access authorization. Both the

JDBC OCI and JDBC Thin drivers support all the Oracle Advanced Security features.

9-1

Note:

If you want to use the security policy file for JDBC

ojdbc.policy

, then you

can download the file from the following link:

http://www.oracle.com/technetwork/index.html

The

ojdbc.policy

file contains the granted permissions that you need to run

your application in control environment of the Java Security Manager. You

can either use this file itself as your Java policy file, or get contents from this

file and add the content in your Java policy file. This file contains permissions

like:

• A few mandatory permissions that are always required, for example,

permission

java.util.PropertyPermission "user.name", "read";

• A few driver-specific permissions, for example, JDBC OCI driver needs

permission

java.lang.RuntimePermission "loadLibrary.ocijdbc12";

• A few feature-based permissions, for example, permissions related to

XA, XDB, FCF and so on

You can set the system properties mentioned in the file or direct values for

permissions as per your requirement.

This chapter contains the following sections:

• Support for Token-Based Authentication

• Support for Oracle Advanced Security

• Support for Login Authentication

• Support for Strong Authentication

• Support for Network Encryption and Integrity

• Support for SSL

• Support for Kerberos

• Support for RADIUS

• About Secure External Password Store

9.1 Support for Token-Based Authentication

In Oracle Database release 21c (21.6.0.0.1), the JDBC Thin drivers provide generic

support for OAuth 2.0, which also includes support for Azure Active Directory (Azure

AD).

While connecting to the database, the JDBC application provides a token to the

database. The database verifies the token with a public key that it requests from the

authentication service, and retrieves the corresponding user group membership

information to find the database schema and role mappings to complete the user

authorization to the database.

Additionally, in case of Oracle Cloud Infrastructure (OCI) Identity and Access

Management (IAM), the application sends a signed header, which proves that it

Chapter 9

Support for Token-Based Authentication

9-2

possesses a private key that is paired to a public key embedded in the token. If both the

token and the signature are valid, and there exists a mapping between the IAM user and a

database user, then access to the database is granted to the JDBC application.

The token-based authentication is supported in the following ways:

Using the File System

When a database token is available on the file system, for example, if you use the Oracle

Cloud Infrastructure Command-Line Interface (OCI CLI), then you can configure the JDBC

driver to use this token for connecting to the Database. You can use the

CONNECTION_PROPERTY_TOKEN_AUTHENTICATION

for this purpose, which can be specified in the

following ways:

• As an

ojdbc.properties

file

• As a JVM system property

• As a parameter in the query section of a connection string

• With a

Properties

object passed to

OracleDataSource.setConnectionProperties(Properties)

• As a parameter in the

SECURITY

section of an Oracle Net Descriptor

JDBC supports the following two types of connection strings, where you can specify this

parameter:

• As an Oracle Net descriptor, where you can specify the parameter as:

jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(HOST=dbhost)(PORT=1522)

(PROTOCOL=tcps))(SECURITY=(SSL_SERVER_DN_MATCH=ON)

(TOKEN_AUTH=OCI_TOKEN))(CONNECT_DATA=(SERVICE_NAME=my.example.com)))

• As a connection property, where you can specify the parameter as:

jdbc:oracle:thin:@tcps://dbhost:1522/my.example.com?

oracle.jdbc.tokenAuthentication=OCI_TOKEN&oracle.jdbc.tokenLocation

=”/path/to/my/token”

When

CONNECTION_PROPERTY_TOKEN_AUTHENTICATION

is set to

OCI_TOKEN

, then the

CONNECTION_PROPERTY_TOKEN_LOCATION

specifies the file system path, from where you can

obtain the access tokens. The default location is

$HOME/.oci/db-token/

. You can set this

property to a different value to specify a nondefault location. The path specified by this

property must be a directory containing files named

token

and

oci_db_key.pem

Chapter 9

Support for Token-Based Authentication

9-3

Note:

• If an Oracle Net Descriptor style URL includes the

TOKEN_LOCATION

parameter, then the value of that parameter takes precedence over a

value defined by

CONNECTION_PROPERTY_TOKEN_LOCATION

• The token file must contain a JSON Web Token (JWT) on a single line of

UTF-8 encoded text. The JWT format is specified by RFC 7519.

• The token location must also contain a private key file named

oci_db_key.pem

. The private key file must use the PEM format and

contain the base64 encoding of an RSA private key in the PKCS#8

encoding

You can also set the connection property

CONNECTION_PROPERTY_TOKEN_AUTHENTICATION

(

oracle.jdbc.tokenAuthentication

)

OAUTH

and the connection property

CONNECTION_PROPERTY_TOKEN_LOCATION

(

oracle.jdbc.tokenLocation

) to point to the bearer token on the file system. There is

no default location set in this case, so you must set the location to either of the

following:

• A directory, in which case, the driver loads a file named

token

• A fully qualified file name

You can perform this in the following ways:

• Configuring the

ojdbc.properties

file

# Enable the OAUTH authentication mode

oracle.jdbc.tokenAuthentication=OAUTH

# Specify the location of the Bearer token location

oracle.jdbc.tokenLocation=/home/user1/mytokens/jwtbearertoken

• Using the JDBC URL

jdbc:oracle:thin:@tcps://adb.mydomain.oraclecloud.com:1522/

xyz.adb.oraclecloud.com?

oracle.jdbc.tokenAuthentication=OAUTH&oracle.jdbc.tokenLocation=/

home/user/token

• Using the TNS format for a JDBC URL:

jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCPS)(PORT=1521)

(HOST=adb.mydomain.oraclecloud.com))(CONNECT_DATA=

(SERVICE_NAME=xyz.adb.oraclecloud.com))(SECURITY=(TOKEN_AUTH=OAUTH)

(TOKEN_LOCATION=/home/user1/mytokens/jwtbearertoken)))"

Using the oracle.jdbc.accessToken Connection Property

Set the

CONNECTION_PROPERTY_ACCESS_TOKEN

(

oracle.jdbc.accessToken

) to the

access token value. You can perform this in the following ways:

Chapter 9

Support for Token-Based Authentication

9-4

Note:

You must enclose the token value with double quotation marks ("") to escape the

equal signs (=) that may appear in the token value.

• Using the JDBC URL

jdbc:oracle:thin:@tcps://adb.mydomain.oraclecloud.com:1522/

xyz.adb.oraclecloud.com?oracle.jdbc.accessToken="ey...5c"

• Using the Descriptor URL

jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcps)(HOST=mydomain.com)

(PORT=5525))

(CONNECT_DATA=(SERVICE_NAME=myservice.com)))?

oracle.jdbc.accessToken="ey...5c"

• Configuring the

ojdbc.properties

File

# Enable the OAUTH authentication mode

oracle.jdbc.accessToken="ey...5c"

Or,

# Enable the OAUTH authentication mode

oracle.jdbc.accessToken=${DATABASE_ACCESS_TOKEN}

Where, the access token is the value of the

DATABASE_ACCESS_TOKEN

environment

variable.

Note:

You do not need to set

oracle.jdbc.tokenAuthentication=OAUTH

as the driver

automatically sets the

OAUTH

mode, when the access token is provided.

Using the OracleConnectionBuilder Interface

Call the

OracleConnectionBuilder.accessToken

method for authentication with a database

access token. This method accepts a token value that the application obtains from the

authentication service. If you pass a token using this method, then it overrides the connection

string setting of

TOKEN_AUTH=OCI_TOKEN

in case of OCI IAM, or

TOKEN_AUTH=OAUTH

in case of

Azure AD, which means that JDBC does not read the token from the file system as it typically

does. Instead, JDBC uses the

AccessToken

object provided to the

accessToken

method.

In case of OCI IAM, JDBC also generates a signature using the private key and sends it to

the Database along with the IAM database access token. First, the Database verifies the

token with the public signing key from IAM. Then, it verifies the JDBC-generated signature by

decrypting it with a public key that is embedded in the token. If the decrypted signature is

valid, then it proves that JDBC possesses the private key.

Chapter 9

Support for Token-Based Authentication

9-5

A single instance of the

OracleDataSource

class, configured with a single URL,

creates instances of the

OracleConnectionBuilder

interface. These instances support

traditional authentication with O5Logon, while also supporting token-based

authentication. The application then calls the methods to configure a user and a

password, or calls methods to configure a token. However, it is invalid to configure this

builder with both a token and with a user name or a password. If both the

accessToken

method and the

password

user

methods are invoked with non-null values, then a

SQLException

, indicating an invalid configuration, is thrown when creating a

connection with this builder.

Using the OracleDataSource Class

Call the

OracleCommonDataSource.setTokenSupplier(AccessToken accessToken)

method for authentication with a database access token. This method sets a supplier

function that generates an access token when creating a connection with this

DataSource

. The supplier function is invoked each time this

DataSource

creates a

connection. Instances of access tokens, which are generated by the supplier, must

represent a token type that is supported by Oracle Database for client authentication.

The supplier must be thread safe.

Note:

Use the

AccessToken.createJsonWebTokenCache(Supplier)

method to

create a thread safe Supplier that caches tokens from a user defined

Supplier.

It is invalid to configure this

DataSource

with both a token supplier and with a user

name or password. If you invoke the

setUser(String)

setPassword(String)

setConnectionProperties(java.util.Properties)

, or

setConnectionProperty(String, String)

methods to configure this

DataSource

with

a user name or a password, and also invoke the

setTokenSuppliersetTokenSupplier(AccessToken accessToken)

method to

configure a token supplier, then a

SQLException

indicating an invalid configuration is

thrown, when creating a connection with this

DataSource

The access tokens are ephemeral in nature and expire within an hour or less. So, use

the

Supplier

type that enables an instance of the

OracleDataSource

class to obtain a

newly generated token, each time it creates a connection. The

Supplier

can generate

the same token multiple times, until the expiration time of that token passes. After the

expiration time of a token is over, the

Supplier

must no longer generate that token,

and instead begin to generate a new token with a later expiration time.

See Also:

• Authenticating and Authorizing IAM Users for Oracle Autonomous

Databases

• Use Azure Active Directory (Azure AD) with Autonomous Database

• About TCP/IP with SSL Protocol

Chapter 9

Support for Token-Based Authentication

9-6

9.2 Support for Oracle Advanced Security

This section describes the following concepts:

• Overview of Oracle Advanced Security

• JDBC OCI Driver Support for Oracle Advanced Security

• JDBC Thin Driver Support for Oracle Advanced Security

9.2.1 Overview of Oracle Advanced Security

Oracle Advanced Security provides the following security features:

• Network Encryption

Sensitive information communicated over enterprise networks and the Internet can be

protected by using encryption algorithms, which transform information into a form that

can be deciphered only with a decryption key. For example, AES.

To ensure network integrity during transmission, Oracle Advanced Security generates a

cryptographically secure message digest. Starting from Oracle Database 12c Release 1

(12.1), the SHA-2 list of hashing algorithms are also supported and Oracle Advanced

Security uses the following hashing algorithms to generate the secure message digest

and includes it with each message sent across a network.

This protects the communicated data from attacks, such as data modification, deleted

packets, and replay attacks.

The following code snippet shows how to calculate the checksum using any of the

algorithms mentioned previously:

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_CHECKSUM_TYPES,

"( SHA1)");

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_CHECKSUM_LEVEL,

"REQUIRED");

• Strong Authentication

To ensure network security in distributed environments, it is necessary to authenticate the

user and check his credentials. Password authentication is the most common means of

authentication. Oracle Database enables strong authentication with Oracle authentication

adapters, which support various third-party authentication services, including SSL with

digital certificates. Oracle Database supports the following industry-standard

authentication methods:

– Kerberos

– Remote Authentication Dial-In User Service (RADIUS)

– Secure Sockets Layer (SSL)

See Also:

Oracle Database Security Guide

Chapter 9

Support for Oracle Advanced Security

9-7

9.2.2 JDBC OCI Driver Support for Oracle Advanced Security

If you are using the JDBC OCI driver, which presumes that you are running from a

computer with an Oracle client installation, then support for Oracle Advanced Security

and incorporated third-party features is fairly similar to the support provided by in any

Oracle client situation. Your use of Advanced Security features is determined by

related settings in the

sqlnet.ora

file on the client computer.

Note:

Starting from Oracle Database 12c Release 1 (12.1), Oracle recommends

you to use the configuration parameters present in the new XML

configuration file

oraaccess.xml

instead of the OCI-specific configuration

parameters present in the

sqlnet.ora

file. However, the configuration

parameters present in the

sqlnet.ora

file are still supported.

The JDBC OCI driver attempts to use external authentication if you try connecting to a

database without providing a password. The following are some examples using the

JDBC OCI driver to connect to a database without providing a password:

SSL Authentication

The following code snippet shows how to use SSL authentication to connect to the

database:

Example 9-1 Using SSL Authentication to Connect to the Database

import java.sql.*;

import java.util.Properties;

public class test

{

public static void main( String [] args ) throws Exception

{

String url = "jdbc:oracle:oci:@"

+"(DESCRIPTION=(ADDRESS=(PROTOCOL=tcps)(HOST=localhost)(PORT=5221))"

+"(CONNECT_DATA=(SERVICE_NAME=orcl)))";

Driver driver = new oracle.jdbc.OracleDriver();

Properties props = new Properties();

Connection conn = driver.connect( url, props );

conn.close();

}

Using a Data Source

The following code snippet shows how to use a data source to connect to the

database:

Example 9-2 Using a Data Source to Connect to the Database

import java.sql.*;

import javax.sql.*;

import java.util.Properties;

import oracle.jdbc.pool.*;

Chapter 9

Support for Oracle Advanced Security

9-8

public class testpool {

public static void main( String args ) throws Exception

{ String url = "jdbc:oracle:oci:@" +"(DESCRIPTION=(ADDRESS=(PROTOCOL=tcps)

(HOST=localhost)(PORT=5221))"

+"(CONNECT_DATA=(SERVICE_NAME=orcl)))";

OracleConnectionPoolDataSource ocpds = new OracleConnectionPoolDataSource();

ocpds.setURL(url);

PooledConnection pc = ocpds.getPooledConnection();

Connection conn = pc.getConnection();

}

Note:

The key exception to the preceding, with respect to Java, is that the Secure Sockets

Layer (SSL) protocol is supported by the Oracle JDBC OCI drivers only if you use

native threads in your application. This requires special attention, because green

threads are generally the default.

9.2.3 JDBC Thin Driver Support for Oracle Advanced Security

The JDBC Thin driver cannot assume the existence of an Oracle client installation or the

presence of the

sqlnet.ora

file. Therefore, it uses a Java approach to support Oracle

Advanced Security. Java classes that implement Oracle Advanced Security are included in

the

ojdbc8.jar

and

ojdbc11.jar

files. Security parameters for encryption and integrity,

usually set in the

sqlnet.ora

file, are set using a Java

Properties

object or through system

properties.

9.3 Support for Login Authentication

Basic login authentication through JDBC consists of user names and passwords, as with any

other means of logging in to an Oracle server. Specify the user name and password through

a Java properties object or directly through the

getConnection

method call. This applies

regardless of which client-side Oracle JDBC driver you are using, but is irrelevant if you are

using the server-side internal driver, which uses a special direct connection and does not

require a user name or password.

Starting with Oracle Database 12c Release 1 (12.1.0.2), the Oracle JDBC Thin driver

supports the

O7L_MR

client ability when you are running your application with a JDK such as

JDK 8, which supports the

PBKDF2-SHA2

algorithm. If you are running an application with JDK

7, then you must add a third-party security provider that supports the

PBKDF2-SHA2

algorithm,

otherwise the driver will not support the new

12a

password verifier that requires the

O7L_MR

client ability.

If you are using Oracle Database 12c Release 1 (12.1.0.2) with the

SQLNET.ALLOWED_LOGON_VERSION_SERVER

parameter set to

12a

, then keep the following points

in mind:

• You must also use the 12.1.0.2 Oracle JDBC Thin driver and JDK 8 or JDK 7 with a third-

party security provider that supports the

PBKDF2-SHA2

algorithm

Chapter 9

Support for Login Authentication

9-9

• If you use an earlier version of Oracle JDBC Thin driver, then you will get the

following error:

ORA-28040: No matching authentication protocol

• If you use the 12.1.0.2 Oracle JDBC Thin driver with JDK 7, then also you will get

the same error, if you do not add a third-party security provider that supports the

PBKDF2-SHA2

algorithm.

9.4 Support for Strong Authentication

Oracle Advanced Security enables Oracle Database users to authenticate externally.

External authentication can be with RADIUS, Kerberos, Certificate-Based

Authentication, Token Cards, and Smart Cards. This is called strong authentication.

Oracle JDBC drivers provide support for the following strong authentication methods:

• Kerberos

• RADIUS

• SSL (certificate-based authentication)

See Also:

Oracle Database Net Services Reference

9.5 Support for Network Encryption and Integrity

The section describes the support for network encryption and integrity.

Note:

• Starting with Oracle Database 21c, older encryption and hashing

algorithms are deprecated.

The deprecated algorithms for

DBMS_CRYPTO

and native network

encryption include MD4, MD5, DES, 3DES, and RC4-related algorithms

as well as 3DES for Transparent Data Encryption (TDE). Removing

older, less secure cryptography algorithms prevents accidental use of

these algorithms. To meet your security requirements, Oracle

recommends that you use more modern cryptography algorithms, such

as the Advanced Encryption Standard (AES).

• Oracle provides a patch that you can download to address necessary

security enhancements that affect native network encryption

environments in Oracle Database release 11.2 and later. This patch is

available in My Oracle Support note 2118136.2.

Chapter 9

Support for Strong Authentication

9-10

See Also:

Oracle Database Security Guide

This section describes the following concepts:

• Overview of JDBC Support for Data Encryption and Integrity

• JDBC OCI Driver Support for Encryption and Integrity

• JDBC Thin Driver Support for Encryption and Integrity

• Setting Encryption and Integrity Parameters in Java

9.5.1 Overview of JDBC Support for Network Encryption and Integrity

You can use Oracle Database and Oracle Advanced Security network encryption and

integrity features in your Java database applications, depending on related settings in the

server. When using the JDBC OCI driver, set parameters as you would in any Oracle client

situation. When using the Thin driver, set parameters through a Java properties object.

Encryption is enabled or disabled based on a combination of the client-side encryption-level

setting and the server-side encryption-level setting. Similarly, integrity is enabled or disabled

based on a combination of the client-side integrity-level setting and the server-side integrity-

level setting.

Encryption and integrity support the same setting levels,

REJECTED

ACCEPTED

REQUESTED

, and

REQUIRED

. Table 9-1 shows how these possible settings on the client-side and server-side

combine to either enable or disable the feature. By default, remote OS authentication

(through TCP) is disabled in the database for security reasons.

Table 9-1 Client/Server Negotiations for Encryption or Integrity

Client/Server Settings

Matrix

Client Rejected Client Accepted

(default)

Client

Requested

Client Required

Server Rejected

OFF OFF OFF connection fails

Server Accepted

(default)

OFF OFF ON ON

Server Requested

OFF ON ON ON

Server Required

connection fails ON ON ON

Table 9-1 shows, for example, that if encryption is requested by the client, but rejected by the

server, it is disabled. The same is true for integrity. As another example, if encryption is

accepted by the client and requested by the server, it is enabled. The same is also true for

integrity.

See Also:

Oracle Database Security Guide for more information about network encryption and

integrity features

Chapter 9

Support for Network Encryption and Integrity

9-11

Note:

The term checksum still appears in integrity parameter names, but is no

longer used otherwise. For all intents and purposes, checksum and integrity

are synonymous.

9.5.2 JDBC OCI Driver Support for Encryption and Integrity

If you are using the JDBC OCI driver, which presumes an Oracle-client setting with an

Oracle client installation, then you can enable or disable network encryption or integrity

and set related parameters as you would in any Oracle client situation, through

settings in the

sqlnet.ora

file on the client.

Note:

Starting from Oracle Database 12c Release 1 (12.1), Oracle recommends

you to use the configuration parameters present in the new XML

configuration file

oraaccess.xml

instead of the OCI-specific configuration

parameters present in the

sqlnet.ora

file. However, the configuration

parameters present in the

sqlnet.ora

file are still supported.

To summarize, the client parameters are shown in Table 9-2:

Table 9-2 OCI Driver Client Parameters for Encryption and Integrity

Parameter Description Parameter Name Possible Settings

Client encryption level

SQLNET.ENCRYPTION_CLIENT REJECTED ACCEPTED

REQUESTED

REQUIRED

Client encryption selected list

SQLNET.ENCRYPTION_TYPES_CLIENT AES128

AES192

AES256

Client integrity level

SQLNET.CRYPTO_CHECKSUM_CLIENT REJECTED ACCEPTED

REQUESTED

REQUIRED

Client integrity selected list

SQLNET.CRYPTO_CHECKSUM_TYPES_CLIENT SHA-1

9.5.3 JDBC Thin Driver Support for Encryption and Integrity

The JDBC Thin driver support for network encryption and integrity parameter settings

parallels the JDBC OCI driver support discussed in the preceding section. You can set

the corresponding parameters through a Java properties object that you can use while

opening a database connection.

The default value for the encryption and integrity level is

ACCEPTED

for both the server

side and the client side. This enables you to achieve the desired security level for a

connection pair by configuring only one side of a connection, either the server side or

the client side. This increases the efficiency of your program because if there are

multiple Oracle clients connecting to an Oracle Server, then you need to change the

Chapter 9

Support for Network Encryption and Integrity

9-12

encryption and integrity level to

REQUESTED

in the

sqlnet.ora

file only on the server side to

turn on encryption or integrity for all connections. This saves time and effort because you do

not have to change the settings for each client separately.

Table 9–3 lists the parameter information for the JDBC Thin driver. These parameters are

defined in the

oracle.jdbc.OracleConnection

interface.

Table 9-3 Thin Driver Client Parameters for Encryption and Integrity

Parameter Name Parameter

Type

Possible Settings

CONNECTION_PROPERTY_THIN_NET_ENCRYPTION_LEVEL String REJECTED ACCEPTED REQUESTED

REQUIRED

CONNECTION_PROPERTY_THIN_NET_ENCRYPTION_TYPES String AES256

AES192

AES128

CONNECTION_PROPERTY_THIN_NET_CHECKSUM_LEVEL String REJECTED ACCEPTED REQUESTED

REQUIRED

CONNECTION_PROPERTY_THIN_NET_CHECKSUM_TYPES String SHA1

Note:

• Oracle Advanced Security support for the Thin driver is incorporated directly

into the JDBC classes JAR file. So, there is no separate version for domestic

and export editions. Only parameter settings that are suitable for an export

edition are possible.

9.5.4 Setting Encryption and Integrity Parameters in Java

Use a Java properties object, that is, an instance of

java.util.Properties

, to set the

network encryption and integrity parameters supported by the JDBC Thin driver.

The following example instantiates a Java properties object, uses it to set each of the

parameters in Table 9-3, and then uses the properties object in opening a connection to the

database:

...

Properties prop = new Properties();

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_ENCRYPTION_LEVEL,

"REQUIRED");

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_ENCRYPTION_TYPES,

"( AES256 )");

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_CHECKSUM_LEVEL,

"REQUESTED");

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_CHECKSUM_TYPES,

"( SHA1 )");

OracleDataSource ods = new OracleDataSource();

ods.setConnectionProperties(prop);

ods.setURL("jdbc:oracle:thin:@localhost:5221:main");

Connection conn = ods.getConnection();

...

Chapter 9

Support for Network Encryption and Integrity

9-13

The parentheses around the values encryption type and checksum type allow for lists

of values. When multiple values are supplied, the server and the client negotiate to

determine which value is to be actually used.

Example

Example 9-3 is a complete class that sets network encryption and integrity parameters

before connecting to a database to perform a query.

Note:

In the example, the string

REQUIRED

is retrieved dynamically through the

functionality of the

AnoServices

and

Service

classes. You have the option of

retrieving the strings in this manner or including them in the software code as

shown in the previous examples.

Before running this example, you must turn on encryption in the

sqlnet.ora

file. For

example, the following lines will turn on AES256, AES192, and AES128 for the

encryption and SHA1 for the checksum:

SQLNET.ENCRYPTION_SERVER = ACCEPTED

SQLNET.CRYPTO_CHECKSUM_SERVER = ACCEPTED

SQLNET.CRYPTO_CHECKSUM_TYPES_SERVER = (SHA1)

SQLNET.ENCRYPTION_TYPES_SERVER = (AES256, AES192, AES128)

Example 9-3 Setting Network Encryption and Integrity Parameters

import java.sql.*;

import java.util.Properties;

import oracle.net.ano.AnoServices;

import oracle.jdbc.*;

import oracle.jdbc.pool.*;

public class DemoAESAndSHA1

{

static final String USERNAME= "HR";

static final String PASSWORD= "hr";

static final String URL =

"jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost)

(PORT=5221))"

+"(CONNECT_DATA=(SERVICE_NAME=orcl)))";

public static final void main(String[] argv)

{

DemoAESAndSHA1 demo = new DemoAESAndSHA1();

try

{

demo.run();

}catch(SQLException ex)

{

ex.printStackTrace();

}

Chapter 9

Support for Network Encryption and Integrity

9-14

void run() throws SQLException

{

OracleDataSource ods = new OracleDataSource();

Properties prop = new Properties();

// We require the connection to be encrypted with either AES256 or

AES192.

// If the database does not accept such a security level, then the

connection attempt will fail.

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_ENCRYPTION_LEV

EL, AnoServices.ANO_REQUIRED);

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_ENCRYPTION_TYP

ES, "( " + AnoServices.ENCRYPTION_AES256 + "," +

AnoServices.ENCRYPTION_AES192 + ")");

// We also require the use of the SHA1 algorithm for network integrity

checking.

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_CHECKSUM_LEVEL

, AnoServices.ANO_REQUIRED);

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_CHECKSUM_TYPES

, "( " + AnoServices.CHECKSUM_SHA1 + " )");

prop.setProperty("user", DemoAESAndSHA1.USERNAME);

prop.setProperty("password", DemoAESAndSHA1.PASSWORD);

ods.setConnectionProperties(prop);

ods.setURL(DemoAESAndSHA1.URL);

OracleConnection oraConn = (OracleConnection) ods.getConnection();

System.out.println("Connection created! Encryption algorithm is: " +

oraConn.getEncryptionAlgorithmName() + ", network integrity algorithm is: "

+ oraConn.getDataIntegrityAlgorithmName());

oraConn.close();

}

9.6 Support for SSL

This section describes the following topics:

• Overview of JDBC Support for SSL

• About Managing Certificates and Wallets

• About Keys and certificates containers

• Database Connectivity Over TLS Version 1.2 Using JDBC Thin and JKS

• Automatic SSL Connection Configuration

• Support for Key Store Service

Chapter 9

Support for SSL

9-15

9.6.1 Overview of JDBC Support for SSL

Oracle Database 19c provides support for the Secure Sockets Layer (SSL) protocol.

SSL is a widely used industry standard protocol that provides secure communication

over a network. SSL provides authentication, data encryption, and data integrity. It

provides a secure enhancement to the standard TCP/IP protocol, which is used for

Internet communication.

SSL uses digital certificates that comply with the X.509v3 standard for authentication

and a public and private key pair for encryption. SSL also uses secret key

cryptography and digital signatures to ensure privacy and integrity of data. When a

network connection over SSL is initiated, the client and server perform an SSL

handshake that includes the following steps:

• Client and server negotiate about the cipher suites to use. This includes deciding

on the encryption algorithms to be used for data transfer.

• Server sends its certificate to the client, and the client verifies that the certificate

was signed by a trusted certification authority (CA). This step verifies the identity of

the server.

• If client authentication is required, the client sends its own certificate to the server,

and the server verifies that the certificate was signed by a trusted CA.

• Client and server exchange key information using public key cryptography. Based

on this information, each generates a session key. All subsequent communications

between the client and the server is encrypted and decrypted by using this set of

session keys and the negotiated cipher suite.

Note:

In Oracle Database 11g Release 1 (11.1), SSL authentication is supported in

the thin driver. So, you do not need to provide a user name/password pair if

you are using SSL authentication.

SSL Terminology

The following terms are commonly used in the SSL context:

• Certificate: A certificate is a digitally signed document that binds a public key with

an entity. The certificate can be used to verify that the public key belongs to that

individual.

• Certification authority: A certification authority (CA), also known as certificate

authority, is an entity which issues digitally signed certificates for use by other

parties.

• Cipher suite: A cipher suite is a set of cryptographic algorithms and key sizes

used to encrypt data sent over an SSL-enabled network.

• Private key: A private key is a secret key, which is never transmitted over a

network. The private key is used to decrypt a message that has been encrypted

using the corresponding public key. It is also used to sign certificates. The

certificate is verified using the corresponding public key.

Chapter 9

Support for SSL

9-16

• Public key: A public key is an encryption key that can be made public or sent by ordinary

means such as an e-mail message. The public key is used for encrypting the message

sent over SSL. It is also used to verify a certificate signed by the corresponding private

key.

• Key Store or Wallet: A wallet is a password-protected container that is used to store

authentication and signing credentials, including private keys, certificates, and trusted

certificates required by SSL.

• Security Provider: A Java implementation that provides some functionality related to

security. A provider is responsible for decoding a key store file.

• Key Store Service (KSS): A component of Oracle Platform Security services. KSS

enables a key store to be referenced as a URI with

kss://

scheme (rather than a file

name).

Java Version of SSL

The Java Secure Socket Extension (JSSE) provides a framework and an implementation for

a Java version of the SSL and TLS protocols. JSSE provides support for data encryption,

server and client authentication, and message integrity. It abstracts the complex security

algorithms and handshaking mechanisms and simplifies application development by

providing a building block for application developers, which they can directly integrate into

their applications. JSSE is integrated into Java Development Kit (JDK) 1.4 and later, and

supports SSL version 2.0 and 3.0.

Oracle strongly recommends that you have a clear understanding of the JavaTM Secure

Socket Extension (JSSE) framework before using SSL in the Oracle JDBC drivers.

The JSSE standard application programming interface (API) is available in the

javax.net

javax.net.ssl

, and

javax.security.cert

packages. These packages provide classes for

creating and configuring sockets, server sockets, SSL sockets, and SSL server sockets. The

packages also provide a class for secure HTTP connections, a public key certificate API

compatible with JDK1.1-based platforms, and interfaces for key and trust managers.

SSL works the same way, as in any networking environment, in Oracle Database 18c.

Note:

In order to use JSSE in your program, you must have clear understanding of

JavaTM Secure Socket Extension (JSSE) framework.

9.6.2 About Managing Certificates and Wallets

To establish an SSL connection with a JDBC client, Thin or OCI, Oracle database server

sends its certificate, which is stored in its wallet. The client may or may not need a certificate

or wallet depending on the server configuration.

The Oracle JDBC Thin driver uses the JSSE framework to create an SSL connection. It uses

the default provider (SunJSSE) to create an SSL context. However you can provide your own

provider.

You do not need a certificate for the client, unless the

SSL_CLIENT_AUTHENTICATION

parameter is set on the server.

Chapter 9

Support for SSL

9-17

9.6.3 About Keys and certificates containers

Java clients can use multiple types of containers such as Oracle wallets, JKS,

PKCS12, and so on, as long as a provider is available. For Oracle wallets, OraclePKI

provider must be used because the PKCS12 support provided by SunJSSE provider

does not support all the features of PKCS12. In order to use OraclePKI provider, the

following JARs are required:

•

oraclepki.jar

•

osdt_cert.jar

•

osdt_core.jar

All these JAR files should be under

$ORACLE_HOME/jlib directory

9.6.4 Database Connectivity Over TLS Version 1.2 Using JDBC Thin

and JKS

This section describes the steps to configure the Oracle JDBC thin driver to connect to

the Database using SSL v1.2.

• Always use the latest update of the JDK

Use the latest update of either JDK 11 or JDK 8 because the updated versions

include bug fixes that are required for using SSL version 1.2.

• Install the JCE files

Install the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction

Policy Files because irrespective of the JDK version that you use, the strong

cipher suites (for example

TLS_RSA_WITH_AES_256_CBC_SHA256

) are not enabled

without them.

• Use JKS files or wallets

Note:

Starting from Oracle Database Release 18c, you can specify TLS

configuration properties in a new configuration file called

ojdbc.properties

. The use of this file eases the connectivity to

Database services on Cloud.

See Also:

Oracle Database JDBC Java API Reference

After performing all the preceding steps, if you run into more issues, then you can turn

on tracing to diagnose the problems using -

Djavax.net.debug=all

option.

9.6.5 Automatic SSL Connection Configuration

Chapter 9

Support for SSL

9-18

Starting from Oracle Database Release 18c, you can use default values or programmatic

logic for resolving the connection configuration values without manually adding or updating

the security provider. You can resolve the configuration values in the following two ways:

• Provider Resolution

• Automatic Key Store Type (KSS) Resolution

9.6.5.1 Provider Resolution

For certain key store types, the JDBC driver can resolve the provider implementation that is

used to load the key store. For these types, it is not necessary to register the provider with

Java security. As long as the provider implementation is on the

CLASSPATH

, the driver can

instantiate the security provider.

The following key store types map to a known provider:

• SSO:

oracle.security.pki.OraclePKIProvider

• KSS:

oracle.security.jps.internal.keystore.provider.FarmKeyStoreProvider

The driver attempts to resolve the provider only if there is no provider registered for the

specified type.

If the

oraclepki.jar

file is on the CLASSPATH, then the driver can automatically load the

Oracle PKI Provider in the following way:

java –cp oraclepki.jar:ojdbc8.jar –D javax.net.ssl.keyStore=/path/to/wallet/

cwallet.sso MyApp

Similarly, for a specified value of the

oracle.net.wallet_location

connection property, the

driver can automatically load the Oracle PKI Provider in the following way:

java –cp .:oraclepki.jar:ojdbc8.jar –D oracle.net.wallet_location=file:/

path/to/wallet/cwallet.sso MyApp

Note:

For PKCS12 types created by the orapki tool (The

ewallet.p12

file), you may still

need to register the

OraclePKIProvider

with Java security because the PKCS12

file created by the orapki tool includes the ASN1 Key Bag element (Type Code:

1.2.840.113549.1.12.10.1.1). The Sun PKCS12 implementation does not support

the Key Bag type and throws an error when attempting to read the

ewallet.p12

file.

For HotSpot and Open JDK users, the Sun Provider comes bundled as the PKCS12

provider. This means that the PKCS12 provider will already have a registered

provider, and the driver will make no attempt to override this.

9.6.5.2 Automatic Key Store Type (KSS) Resolution

Chapter 9

Support for SSL

9-19

The JDBC driver can resolve common key store types based on the value of the

javax.net.ssl.keyStore

and

javax.net.ssl.trustStore

properties, eliminating the

need to specify the type using these properties.

Key Store or Trust Store with a Recognized File Extension

A key store or trust store with a recognized file extension maps to the following types:

• File extension

.jks

resolves to

javax.net.ssl.keyStoreType

as JKS:

java –cp ojdbc8.jar –D javax.net.ssl.keyStore=/path/to/keystore/

keystore.jks MyApp

• File extension

.sso

resolves to

javax.net.ssl.keyStoreType

as SSO:

java –cp ojdbc8.jar –D

javax.net.ssl.keyStore=/path/to/keystore/keystore.sso MyApp

• File extension

.p12

resolves to

javax.net.ssl.keyStoreType

as PKCS12:

java –cp ojdbc8.jar –D

javax.net.ssl.keyStore=/path/to/keystore/keystore.p12 MyApp

• File extension

.pfx

resolves to

javax.net.ssl.keyStoreType

as PKCS12:

java –cp ojdbc8.jar –D

javax.net.ssl.keyStore=/path/to/keystore/keystore.pfx MyApp

Key Store or Trust Store with a URI

If the key store or the trust store is a URI with a

kss://

scheme, this maps to type

KSS:

java –cp ojdbc8.jar –D

javax.net.ssl.keyStore=kss://MyStripe/MyKeyStore MyApp

Note:

You can set the

javax.net.ssl.trustStoreType

and

javax.net.ssl.keyStoreType

properties for overriding the default type

resolution.

9.6.6 Support for Default SSL Context

For applications that require finer control over the TLS configuration, you can configure

the JDBC driver to use the

SSLContext

returned by the

SSLContext.getDefault

method. Use one of the following methods for the driver to use the default

SSLContext

•

javax.net.ssl.keyStore=NONE

•

javax.net.ssl.trustStore=NONE

Chapter 9

Support for SSL

9-20

You can use the default

SSLContext

to support key store types that are not file-based.

Common examples of such key store types include hardware-based smart cards. Key store

types that require programmatic call to the

load(KeyStore.LoadStoreParameter)

method

also belong to this category.

See Also:

• https://docs.oracle.com/javase/8/docs/api/javax/net/ssl/

SSLContext.html#getDefault--

• https://docs.oracle.com/javase/8/docs/api/java/security/KeyStore.html#load-

java.security.KeyStore.LoadStoreParameter-

9.6.7 Support for Key Store Service

This release of Oracle Database introduces support for Key Store Service (KSS) in the JDBC

driver. So, if you have configured a Key Store Service in a WebLogic server, then JDBC

applications can now integrate with the existing Key Store Service configuration.

The driver can load the key stores that are managed by the Key Store Service. If the value of

the

javax.net.ssl.keyStore

property or the

javax.net.ssl.trustStore

property is a URI

with

kss://

scheme, then the driver loads the key store from Key Store Service.

For permission-based protection, the following permission must be granted to the ojdbc JAR

file:

permission KeyStoreAccessPermission

"stripeName=*,keystoreName=*,alias=*", "read";

This permission grants access to every key store. For limiting the scope of access, you can

replace the asterisk wild cards (*) with a specific application stripe and a key store name. The

driver does not load the key store as a privileged action, which means that the

KeyStoreAccessPermission

must also be granted to the application code base.

9.7 Support for Kerberos

This section discusses the following topics:

• Overview of JDBC Support for Kerberos

• Configuring Windows to Use Kerberos

• Configuring Oracle Database to Use Kerberos

• Code Example for Using Kerberos

9.7.1 Overview of JDBC Support for Kerberos

Kerberos is a network authentication protocol that provides the tools of authentication and

strong cryptography over the network. Kerberos helps you secure your information systems

across your entire enterprise by using secret-key cryptography. The Kerberos protocol uses

strong cryptography so that a client or a server can prove its identity to its server or client

Chapter 9

Support for Kerberos

9-21

across an insecure network connection. After a client and server have used Kerberos

to prove their identity, they can also encrypt all of their communications to assure

privacy and data integrity as they go about their business.

The Kerberos architecture is centered around a trusted authentication service called

the key distribution center, or KDC. Users and services in a Kerberos environment are

referred to as principals; each principal shares a secret, such as a password, with the

KDC. A principal can be a user such as

or a database server instance.

Starting from 12c Release 1, Oracle Database supports cross-realm authentication for

Kerberos. If you add the referred realm appropriately in the

domain_realms

section of

the kerberos configuration file, then being in one particular realm, you can access the

services of another realm.

Starting from Release 19c, Oracle Database supports Kerberos Constrained

Delegation. This feature added a new method

OracleConnectionBuilder

gssCredential(GSSCredential credential)

in the

oracle.jdbc.OracleConnectionBuilder

interface. This method accepts the

GSSCredential of the user and then delegates it during the Kerberos authentication in

the driver.

See Also:

Oracle Database JDBC Java API Reference

9.7.2 Configuring Windows to Use Kerberos

A good Kerberos client providing

klist, kinit,

and other tools, can be found at the

following link:

http://web.mit.edu/kerberos/dist/index.html

This client also provides a nice GUI.

You need to make the following changes to configure Kerberos on your Windows

machine:

1. Right-click the My Computer icon on your desktop.

2. Select Properties. The System Properties dialog box is displayed.

3. Select the Advanced tab.

4. Click Environment Variables. The Environment Variables dialog box is displayed.

5. Click New to add a new user variable. The New User Variable dialog box is

displayed.

6. Enter

KRB5CCNAME

in the Variable name field.

7. Enter

FILE:C:\Documents and Settings\<user_name>\krb5cc

in the Variable

value field.

8. Click OK to close the New User Variable dialog box.

9. Click OK to close the Environment Variables dialog box.

10. Click OK to close the System Properties dialog box.

Chapter 9

Support for Kerberos

9-22

Note:

C:\WINDOWS\krb5.ini

file has the same content as

krb5.conf

file.

9.7.3 Configuring Oracle Database to Use Kerberos

Perform the following steps to configure Oracle Database to use Kerberos:

1. Use the following command to connect to the database:

SQL> connect system

Enter password: password

2. Use the following commands to create a user

[email protected]

that is identified

externally:

SQL> create user "[email protected]" identified externally;

SQL> grant create session to "[email protected]";

3. Use the following commands to connect to the database as

sysdba

and dismount it:

SQL> connect / as sysdba

SQL> shutdown immediate;

4. Add the following line to

$T_WORK/t_init1.ora

file:

OS_AUTHENT_PREFIX=""

5. Use the following command to restart the database:

SQL> startup pfile=t_init1.ora

6. Modify the

sqlnet.ora

file to include the following lines:

names.directory_path = (tnsnames)

#Kerberos

sqlnet.authentication_services = (beq,kerberos5)

sqlnet.authentication_kerberos5_service = dbji

sqlnet.kerberos5_conf = /home/Jdbc/Security/kerberos/krb5.conf

sqlnet.kerberos5_keytab = /home/Jdbc/Security/kerberos/dbji.oracleserver

sqlnet.kerberos5_conf_mit = true

sqlnet.kerberos_cc_name = /tmp/krb5cc_5088

# logging (optional):

trace_level_server=16

trace_directory_server=/scratch/sqlnet/

7. Use the following commands to verify that you can connect through SQL*Plus:

> kinit client

> klist

Ticket cache: FILE:/tmp/krb5cc_5088

Default principal: [email protected]

Valid starting Expires Service principal

06/22/06 07:13:29 06/22/06 17:13:29 krbtgt/[email protected]

Kerberos 4 ticket cache: /tmp/tkt5088

klist: You have no tickets cached

> sqlplus '/@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracleserver.mydomain.com)

Chapter 9

Support for Kerberos

9-23

(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=orcl)))'

9.7.4 Code Example for Using Kerberos

This following example demonstrates the new Kerberos authentication feature that is

part of Oracle Database 12c Release 1 (12.1) JDBC thin driver. This demo covers two

scenarios:

• In the first scenario, the OS maintains the user name and credentials. The

credentials are stored in the cache and the driver retrieves the credentials before

trying to authenticate to the server. This scenario is in the module

connectWithDefaultUser()

Note:

1. Before you run this part of the demo, use the following command to

verify that you have valid credentials:

> /usr/kerberos/bin/kinit client

where, the password is welcome.

2. Use the following command to list your tickets:

> /usr/kerberos/bin/klist

• The second scenario covers the case where the application wants to control the

user credentials. This is the case of the application server where multiple web

users have their own credentials. This scenario is in the module

connectWithSpecificUser().

Note:

To run this demo, you need to have a working setup, that is, a Kerberos

server up and running, and an Oracle database server that is configured

to use Kerberos authentication. You then need to change the URLs used

in the example to compile and run it.

Example 9-4 Using Kerberos Authentication to Connect to the Database

import com.sun.security.auth.module.Krb5LoginModule;

import java.io.IOException;

import java.security.PrivilegedExceptionAction;

import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.HashMap;

import java.util.Properties;

import javax.security.auth.Subject;

import javax.security.auth.callback.Callback;

import javax.security.auth.callback.CallbackHandler;

Chapter 9

Support for Kerberos

9-24

import javax.security.auth.callback.PasswordCallback;

import javax.security.auth.callback.UnsupportedCallbackException;

import oracle.jdbc.OracleConnection;

import oracle.jdbc.OracleDriver;

import oracle.net.ano.AnoServices;

public class KerberosJdbcDemo

{

String url ="jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)"+

"(HOST=oracleserver.mydomain.com)(PORT=5221))(CONNECT_DATA=" +

"(SERVICE_NAME=orcl)))";

public static void main(String[] arv)

{

/* If you see the following error message [Mechanism level: Could not load

* configuration file c:\winnt\krb5.ini (The system cannot find the path

* specified] it's because the JVM cannot locate your kerberos config file.

* You have to provide the location of the file. For example, on Windows,

* the MIT Kerberos client uses the config file: C\WINDOWS\krb5.ini:

// System.setProperty("java.security.krb5.conf","C:\\WINDOWS\\krb5.ini");

System.setProperty("java.security.krb5.conf","/home/Jdbc/Security/kerberos/

krb5.conf");

KerberosJdbcDemo kerberosDemo = new KerberosJdbcDemo();

try

{

System.out.println("Attempt to connect with the default user:");

kerberosDemo.connectWithDefaultUser();

}

catch (Exception e)

{

e.printStackTrace();

}

try

{

System.out.println("Attempt to connect with a specific user:");

kerberosDemo.connectWithSpecificUser();

}

catch (Exception e)

{

e.printStackTrace();

}

void connectWithDefaultUser() throws SQLException

{

OracleDriver driver = new OracleDriver();

Properties prop = new Properties();

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_AUTHENTICATION_SERVICES,

"("+AnoServices.AUTHENTICATION_KERBEROS5+")");

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_AUTHENTICATION_KRB5_MUTU

AL,

"true");

/* If you get the following error [Unable to obtain Princpal Name for

* authentication] although you know that you have the right TGT in your

Chapter 9

Support for Kerberos

9-25

* credential cache, then it's probably because the JVM can't locate your

* cache.

* Note that the default location on windows is "C:\Documents and

Settings\krb5cc_username".

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_AUTHENTICATION_KRB

5_CC_NAME,

On linux:

> which kinit

/usr/kerberos/bin/kinit

> ls -l /etc/krb5.conf

lrwxrwxrwx 1 root root 47 Jun 22 06:56 /etc/krb5.conf -> /home/

Jdbc/Security/kerberos/krb5.conf

> kinit client

Password for [email protected]:

> klist

Ticket cache: FILE:/tmp/krb5cc_5088

Default principal: [email protected]

Valid starting Expires Service principal

11/02/06 09:25:11 11/02/06 19:25:11 krbtgt/[email protected]

Kerberos 4 ticket cache: /tmp/tkt5088

klist: You have no tickets cached

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_AUTHENTICATION_KRB

5_CC_NAME,

"/tmp/krb5cc_5088");

Connection conn = driver.connect(url,prop);

String auth = ((OracleConnection)conn).getAuthenticationAdaptorName();

System.out.println("Authentication adaptor="+auth);

printUserName(conn);

conn.close();

}

void connectWithSpecificUser() throws Exception

{

Subject specificSubject = new Subject();

// This first part isn't really meaningful to the sake of this demo. In

// a real world scenario, you have a valid "specificSubject" Subject that

// represents a web user that has valid Kerberos credentials.

Krb5LoginModule krb5Module = new Krb5LoginModule();

HashMap sharedState = new HashMap();

HashMap options = new HashMap();

options.put("doNotPrompt","false");

options.put("useTicketCache","false");

options.put("principal","[email protected]");

krb5Module.initialize(specificSubject,newKrbCallbackHandler(),sharedState,options

Chapter 9

Support for Kerberos

9-26

);

boolean retLogin = krb5Module.login();

krb5Module.commit();

if(!retLogin)

throw new Exception("Kerberos5 adaptor couldn't retrieve credentials (TGT) from

the cache");

// to use the TGT from the cache:

// options.put("useTicketCache","true");

// options.put("doNotPrompt","true");

// options.put("ticketCache","C:\\Documents and Settings\\user\\krb5cc");

// krb5Module.initialize(specificSubject,null,sharedState,options);

// Now we have a valid Subject with Kerberos credentials. The second scenario

// really starts here:

// execute driver.connect(...) on behalf of the Subject 'specificSubject':

Connection conn =

(Connection)Subject.doAs(specificSubject, new PrivilegedExceptionAction()

{

public Object run()

{

Connection con = null;

Properties prop = new Properties();

prop.setProperty(AnoServices.AUTHENTICATION_PROPERTY_SERVICES,

"(" + AnoServices.AUTHENTICATION_KERBEROS5 + ")");

try

{

OracleDriver driver = new OracleDriver();

con = driver.connect(url, prop);

} catch (Exception except)

{

except.printStackTrace();

}

return con;

}

});

String auth = ((OracleConnection)conn).getAuthenticationAdaptorName();

System.out.println("Authentication adaptor="+auth);

printUserName(conn);

conn.close();

}

void printUserName(Connection conn) throws SQLException

{

Statement stmt = null;

try

{

stmt = conn.createStatement();

ResultSet rs = stmt.executeQuery("select user from dual");

while(rs.next())

System.out.println("User is:"+rs.getString(1));

rs.close();

}

finally

{

if(stmt != null)

stmt.close();

}

Chapter 9

Support for Kerberos

9-27

}

class KrbCallbackHandler implements CallbackHandler

{

public void handle(Callback[] callbacks) throws IOException,

UnsupportedCallbackException

{

for (int i = 0; i < callbacks.length; i++)

{

if (callbacks[i] instanceof PasswordCallback)

{

PasswordCallback pc = (PasswordCallback)callbacks[i];

System.out.println("set password to 'welcome'");

pc.setPassword((new String("welcome")).toCharArray());

} else

{

throw new UnsupportedCallbackException(callbacks[i],

"Unrecognized Callback");

}

9.8 Support for RADIUS

This section describes the following concepts:

• Overview of JDBC Support for RADIUS

• Configuring Oracle Database to Use RADIUS

• Code Example for Using RADIUS

9.8.1 Overview of JDBC Support for RADIUS

Oracle Database 11g Release 1 introduced support for Remote Authentication Dial-In

User Service (RADIUS). RADIUS is a client/server security protocol that is most widely

known for enabling remote authentication and access. Oracle Advanced Security uses

this standard in a client/server network environment to enable use of any

authentication method that supports the RADIUS protocol. RADIUS can be used with

a variety of authentication mechanisms, including token cards and smart cards.

9.8.2 Configuring Oracle Database to Use RADIUS

Perform the following steps to configure Oracle Database to use RADIUS:

1. Use the following command to connect to the database:

SQL> connect system

Enter password: password

2. Use the following commands to create a new user

aso

from within a database:

SQL> create user aso identified externally;

SQL> grant create session to aso;

3. Use the following commands to connect to the database as

sysdba

and dismount

it:

Chapter 9

Support for RADIUS

9-28

SQL> connect / as sysdba

SQL> shutdown immediate;

4. Add the following lines to the

t_init1.ora

file:

os_authent_prefix = ""

Note:

Once the test is over, you need to revert the preceding changes made to the

t_init1.ora file.

5. Use the following command to restart the database:

SQL> startup pfile=?/work/t_init1.ora

6. Modify the

sqlnet.ora

file so that it contains only these lines:

sqlnet.authentication_services = ( beq, radius)

sqlnet.radius_authentication = <RADUIUS_SERVER_HOST_NAME>

sqlnet.radius_authentication_port = 1812

sqlnet.radius_authentication_timeout = 120

sqlnet.radius_secret=/home/Jdbc/Security/radius/radius_key

# logging (optional):

trace_level_server=16

trace_directory_server=/scratch/sqlnet/

7. Use the following command to verify that you can connect through SQL*Plus:

>sqlplus 'aso/1234@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)

(HOST=oracleserver.mydomain.com)(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=orcl)))'

9.8.3 Code Example for Using RADIUS

This example demonstrates the new RADIUS authentication feature that is a part of Oracle

Database 12c Release 1 (12.1) JDBC thin driver. You need to have a working setup, that is, a

RADIUS server up and running, and an Oracle database server that is configured to use

RADIUS authentication. You then need to change the URLs given in the example to compile

and run it.

Example 9-5 Using RADIUS Authentication to Connect to the Database

import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Properties;

import oracle.jdbc.OracleConnection;

import oracle.jdbc.OracleDriver;

import oracle.net.ano.AnoServices;

public class RadiusJdbcDemo

{

String url ="jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)"+

"(HOST=oracleserver.mydomain.com)(PORT=5221))(CONNECT_DATA=" +

"(SERVICE_NAME=orcl)))";

public static void main(String[] arv)

{

RadiusJdbcDemo radiusDemo = new RadiusJdbcDemo();

Chapter 9

Support for RADIUS

9-29

try

{

radiusDemo.connect();

}

catch (Exception e)

{

e.printStackTrace();

}

* This method attempts to logon to the database using the RADIUS

* authentication protocol.

* It should print the following output to stdout:

* -----------------------------------------------------

* Authentication adaptor=RADIUS

* User is:ASO

* -----------------------------------------------------

void connect() throws SQLException

{

OracleDriver driver = new OracleDriver();

Properties prop = new Properties();

prop.setProperty(OracleConnection.CONNECTION_PROPERTY_THIN_NET_AUTHENTICATION_SER

VICES,

"("+AnoServices.AUTHENTICATION_RADIUS+")");

// The user "aso" needs to be properly setup on the radius server with

// password "1234".

prop.setProperty("user","aso");

prop.setProperty("password","1234");

Connection conn = driver.connect(url,prop);

String auth = ((OracleConnection)conn).getAuthenticationAdaptorName();

System.out.println("Authentication adaptor="+auth);

printUserName(conn);

conn.close();

}

void printUserName(Connection conn) throws SQLException

{

Statement stmt = null;

try

{

stmt = conn.createStatement();

ResultSet rs = stmt.executeQuery("select user from dual");

while(rs.next())

System.out.println("User is:"+rs.getString(1));

rs.close();

}

finally

{

if(stmt != null)

stmt.close();

}

Chapter 9

Support for RADIUS

9-30

9.9 Secure External Password Store

For large-scale deployments where applications use password credentials to connect to

databases, you can use a client-side Oracle wallet to store such credentials. An Oracle wallet

is a secure software container that is used to store authentication and sign-in credentials.

Storing database password credentials in a client-side Oracle wallet eliminates the need to

embed user names and passwords in application code, batch jobs, or scripts. This reduces

the risk of exposing passwords in the scripts and application code, and simplifies

maintenance because you do not need to change your code each time user names and

passwords change. In addition, if you do not have to change the application code, then it also

becomes easier to enforce password management policies for these user accounts.

You can set the

oracle.net.wallet_location

connection property to specify the wallet

location. The JDBC driver can then retrieve the user name and password pair from this

wallet.

Note:

When an Oracle wallet is opened in a JDBC application, for security reasons, the

wallet file permissions are changed to make it accessible only to the wallet owner

(creator).

See Also:

• Oracle Database Administrator's Guide for more information about configuring

your client to use secure external password store and for information about

managing credentials in it

• Oracle Database Security Guide for more information about managing the

secure external password store for password credentials

Chapter 9

Secure External Password Store

9-31

Proxy Authentication

Oracle Java Database Connectivity (JDBC) provides proxy authentication, also called N-tier

authentication. This feature is supported through both the JDBC Oracle Call Interface (OCI)

driver and the JDBC Thin driver. This chapter contains the following sections:

• About Proxy Authentication

• Types of Proxy Connections

• Creating Proxy Connections

• Closing a Proxy Session

• Caching Proxy Connections

• Limitations of Proxy Connections

Note:

Oracle Database supports proxy authentication functionality in three tiers only. It

does not support it across multiple middle tiers.

10.1 About Proxy Authentication

Proxy authentication is the process of using a middle tier for user authentication. You can

design a middle tier server to proxy clients in a secure fashion by using the following three

forms of proxy authentication:

• The middle tier server authenticates itself with the database server and a client. In this

case, an application user or another application, authenticates itself with the middle tier

server. Client identities can be maintained all the way through to the database.

• The client, that is, a database user, is not authenticated by the middle tier server. The

client's identity and database password are passed through the middle tier server to the

database server for authentication.

• The client, that is, a global user, is authenticated by the middle tier server, and passes

either a Distinguished name (DN) or a Certificate through the middle tier for retrieving the

client's user name.

Note:

Operations done on behalf of a client by a middle tier server can be audited.

In all cases, an administrator must authorize the middle tier server to proxy a client, that is, to

act on behalf of the client. Suppose, the middle tier server initially connects to the database

10-1

as user

and activates a proxy connection as user

jeff

, and then issues the

following statement to authorize the middle tier server to proxy a client:

ALTER USER jeff GRANT CONNECT THROUGH HR;

You can also:

• Specify roles that the middle tier is permitted to activate when connecting as the

client. For example,

CREATE ROLE role1;

GRANT SELECT ON employees TO role1;

ALTER USER jeff GRANT CONNECT THROUGH HR ROLE role1;

The role clause limits the access only to those database objects that are

mentioned in the list of the roles. The list of roles can be empty.

• Find the users who are currently authorized to connect through a middle tier by

querying the

PROXY_USERS

data dictionary view.

• Disallow a proxy connection by using the

REVOKE CONNECT THROUGH

clause of

ALTER USER

statement.

Note:

In case of proxy authentication, a JDBC connection to the database creates

a database session during authentication, and then other sessions can be

created during the life time of the connection.

You need to use the different fields and methods present in the

oracle.jdbc.OracleConnection

interface to set up the different types of proxy

connections.

10.2 Types of Proxy Connections

You can create proxy connections using any one of the following options:

•

USER NAME

This is done by supplying the user name or the password or both. The SQL

statement for specifying authentication using password is:

ALTER USER jeff GRANT CONNECT THROUGH HR AUTHENTICATED USING password;

In this case,

jeff

is the user name and

is the proxy for

jeff

The password option exists for additional security. Having no

authenticated

clause implies default authentication, which is using only the user name without

the password. The SQL statement for specifying default authentication is:

ALTER USER jeff GRANT CONNECT THROUGH HR

•

DISTINGUISHED NAME

This is a global name in lieu of the password of the user being proxied for. An

example of the corresponding SQL statement using a distinguished name is:

Chapter 10

Types of Proxy Connections

10-2

CREATE USER jeff IDENTIFIED GLOBALLY AS

'CN=jeff,OU=americas,O=oracle,L=redwoodshores,ST=ca,C=us';

The string that follows the

identified globally as

clause is the distinguished name. It

is then necessary to authenticate using this distinguished name. The corresponding SQL

statement to specify authentication using distinguished name is:

ALTER USER jeff GRANT CONNECT THROUGH HR AUTHENTICATED USING DISTINGUISHED NAME;

•

CERTIFICATE

This is a more encrypted way of passing the credentials of the user, who is to be proxied,

to the database. The certificate contains the distinguished name encoded in it. One way

of generating the certificate is by creating a wallet and then decoding the wallet to get the

certificate. The wallet can be created using

runutl mkwallet

. It is then necessary to

authenticate using the generated certificate. The SQL statement for specifying

authentication using certificate is:

ALTER USER jeff GRANT CONNECT THROUGH HR AUTHENTICATED USING CERTIFICATE;

Note:

The use of certificates for proxy authentication will be desupported in future

Oracle Database releases.

Note:

• All the options can be associated with roles.

• When opening a new proxied connection, a new session is started on the

Database server. If you start a global transaction and then call the

openProxySession

method, then, at this point, you are no longer a part of the

global transaction and instead it is like you are in a freshly created JDBC

connection. Typically, this never happens because the

openProxySession

method is called prior to creating or resuming a global transaction. In such a

case, you are still a part of the global transaction.

10.3 Creating Proxy Connections

A user, say

jeff

, has to connect to the database through another user, say

. The proxy

user,

, should have an active authenticated connection. A proxy session is then created on

this active connection, with the driver issuing a command to the server to create a session for

the user,

jeff

. The server returns the new session ID, and the driver sends a session switch

command to switch to this new session.

The JDBC OCI and Thin driver switch sessions in the same manner. The drivers permanently

switch to the new session,

jeff

. As a result, the proxy session,

, is not available until the

new session,

jeff

, is closed.

Chapter 10

Creating Proxy Connections

10-3

Note:

You can use the

isProxySession

method from the

oracle.jdbc.OracleConnection

interface to check if the current session

associated with your connection is a proxy session. This method returns

true

if the current session associated with the connection is a proxy session.

A new proxy session is opened by using the following method from the

oracle.jdbc.OracleConnection

interface:

void openProxySession(int type, java.util.Properties prop) throws

SQLExceptionOpens

Where,

type

is the type of the proxy session and can have the following values:

•

OracleConnection.PROXYTYPE_USER_NAME

This type is used for specifying the user name.

•

OracleConnection.PROXYTYPE_DISTINGUISHED_NAME

This type is used for specifying the distinguished name of the user.

•

OracleConnection.PROXYTYPE_CERTIFICATE

This type is used for specifying the proxy certificate.

prop

is the property value of the proxy session and can have the following values:

•

PROXY_USER_NAME

This property value should be used with the type

OracleConnection.PROXYTYPE_USER_NAME

. The value should be a

java.lang.String

•

PROXY_DISTINGUISHED_NAME

This property value should be used with the type

OracleConnection.PROXYTYPE_DISTINGUISHED_NAME

. The value should be a

java.lang.String

•

PROXY_CERTIFICATE

This property value should be used with the type

OracleConnection.PROXYTYPE_CERTIFICATE

. The value is a

bytep[]

array that

contains the certificate.

•

PROXY_ROLES

This property value can be used with the following types:

–

OracleConnection.PROXYTYPE_USER_NAME

–

OracleConnection.PROXYTYPE_DISTINGUISHED_NAME

–

OracleConnection.PROXYTYPE_CERTIFICATE

The value should be a

java.lang.String

•

PROXY_SESSION

Chapter 10

Creating Proxy Connections

10-4

This property value is used with the

method to close the proxy session.

•

PROXY_USER_PASSWORD

This property value should be used with the type

OracleConnection.PROXYTYPE_USER_NAME

. The value should be a

java.lang.String

The following code snippet shows the use of the

openProxySession

method:

java.util.Properties prop = new java.util.Properties();

prop.put(OracleConnection.PROXY_USER_NAME, "jeff");

String[] roles = {"role1", "role2"};

prop.put(OracleConnection.PROXY_ROLES, roles);

conn.openProxySession(OracleConnection.PROXYTYPE_USER_NAME, prop);

10.4 Closing a Proxy Session

You can close the proxy session opened with the

OracleConnection.openProxySession

method by passing the

OracleConnection.PROXY_SESSION

parameter to the

OracleConnection.close

method in the following way:

OracleConnection.close

(OracleConnection.PROXY_SESSION);

This is similar to closing a proxy session on a non-cached connection. The standard

method must be called explicitly to close the connection itself. If the

method is called

directly, without closing the proxy session, then both the proxy session and the connection

are closed. This can be achieved in the following way:

OracleConnection.close(OracleConnection.INVALID_CONNECTION);

10.5 Caching Proxy Connections

Proxy connections, like standard connections, can be cached. Caching proxy connections

enhances the performance. To cache a proxy connection, you need to create a connection

using one of the

getConnection

methods on a cache enabled

OracleDataSource

object.

A proxy connection may be cached in the connection cache using the connection attributes

feature of the connection cache. Connection attributes are name/value pairs that are user-

defined and help tag a connection before returning it to the connection cache for reuse. When

the tagged connection is retrieved, it can be directly used without having to do a round-trip to

create or close a proxy session. Universal Connection Pool supports caching of any user/

password authenticated connection. Therefore, any user authenticated proxy connection can

be cached and retrieved.

It is recommended that proxy connections should not be closed without applying the

connection attributes. If a proxy connection is closed without applying the connection

attributes, the connection is returned to the connection cache for reuse, but cannot be

retrieved. The connection caching mechanism does not remember or reset session state.

A proxy connection can be removed from the connection cache by closing the connection

directly.

Chapter 10

Closing a Proxy Session

10-5

10.6 Limitations of Proxy Connections

Closing a proxy connection automatically closes every SQL Statement created by the

proxy connection, during the proxy session or prior to the proxy session. This may

cause unexpected consequences on application pooling or statement caching. The

following code samples explain this limitation of proxy connections:

Example 1

....

public void displayName(String N) // Any function using the Proxy feature

{

Properties props = new Properties();

props.put("PROXY_USER_NAME", proxyUser);

c.openProxySession(OracleConnection.PROXYTYPE_USER_NAME, props);

.......

c.close(OracleConnection.PROXY_SESSION);

}

public static void main (String args[]) throws SQLException

{

............

PreparedStatement pstmt = conn.prepareStatement("SELECT first_name FROM

EMPLOYEES WHERE employee_id = ?");

pstmt.setInt(1, 205);

ResultSet rs = pstmt.executeQuery();

while (rs.next())

{

displayName(rs.getString(1));

if (rs.isClosed() // The ResultSet is already closed while closing the

connection!

{

throw new Exception("Your ResultSet has been prematurely closed!

Your Statement object is also dead now.");

}

In the preceding example, when you close the proxy connection in the

displayName

method, then the

PreparedStatement

object and the

ResultSet

object also get closed.

So, if you do not check the status of the

ResultSet

object inside loop, then the loop

will fail when the

method is called for the second time.

Example 2

....

PreparedStatement pstmt = conn.prepareStatement("SELECT first_name FROM

EMPLOYEES WHERE employee_id = ?");

pstmt.setString(1, "205");

ResultSet rs = pstmt.executeQuery();

while (rs.next())

{

....

}

Properties props = new Properties();

props.put("PROXY_USER_NAME", proxyUser);

Chapter 10

Limitations of Proxy Connections

10-6

conn.openProxySession(OracleConnection.PROXYTYPE_USER_NAME, props);

.......

conn.close(OracleConnection.PROXY_SESSION);

// Try to use the PreparedStatement again

pstmt.setString(1, "28960");

// This line of code will fail because the Statement is already closed while closing

the connection!

rs = pstmt.executeQuery();

In the preceding example, the

PreparedStatement

object and the

ResultSet

object work fine

before opening the proxy connection. But, if you try to execute the same

PreparedStatement

object after closing the proxy connection, then the statement fails.

Chapter 10

Limitations of Proxy Connections

10-7

Part IV

Data Access and Manipulation

This part provides a chapter that discusses about accessing and manipulating Oracle data. It

also includes chapters that provide information about Java Database Connectivity (JDBC)

support for user-defined object types, large object (LOB) and binary file (BFILE) locators and

data, object references, and Oracle collections, such as nested tables. This part also

provides chapters that discuss the result set functionality in JDBC, JDBC row sets, and

globalization support provided by Oracle JDBC drivers.

Part IV contains the following chapters:

• Accessing and Manipulating Oracle Data

• Java Streams in JDBC

• Working with Oracle Object Types

• Working with LOBs and BFILEs

• Using Oracle Object References

• Working with Oracle Collections

• Result Set

• JDBC RowSets

• Globalization Support

Accessing and Manipulating Oracle Data

This chapter describes Oracle extensions (

oracle.sql.*

formats) and compares them to

standard Java formats (

java.sql.*

). Using Oracle extensions involves casting your result

sets and statements to

OracleResultSet

OracleStatement

OraclePreparedStatement

, and

OracleCallableStatement

, as appropriate, and using the

getOracleObject

setOracleObject

getXXX

, and

setXXX

methods of these classes, where

XXX

corresponds to

the types in the

oracle.sql

package.

This chapter covers the following topics:

• Data Type Mappings

• Data Conversion Considerations

• Result Set and Statement Extensions

• Comparison of Oracle get and set Methods to Standard JDBC

• Using Result Set Metadata Extensions

• About Using SQL CALL and CALL INTO Statements

11.1 Data Type Mappings

The Oracle JDBC drivers support standard JDBC types as well as Oracle-specific data types.

This section documents standard and Oracle-specific SQL-Java default type mappings. This

section contains the following topics:

• Table of Mappings

• Notes Regarding Mappings

11.1.1 Table of Mappings

The following table shows the default mappings between SQL data types, JDBC type codes,

standard Java types, and Oracle extended types.

The SQL Data Types column lists the SQL types that exist in Oracle Database 12c Release 1

(12.1). The JDBC Type Codes column lists data type codes supported by the JDBC standard

and defined in the

java.sql.Types

class or by Oracle in the

oracle.jdbc.OracleTypes

class. For standard type codes, the codes are identical in these two classes.

The Standard Java Types column lists standard types defined in the Java language. The

Oracle Extension Java Types column lists the

oracle.sql.*

Java types that correspond to

each SQL data type in the database. These are Oracle extensions that let you retrieve all

SQL data in the form of an

oracle.sql.*

Java type.

11-1

Note:

In general, the Oracle JDBC drivers are optimized to manipulate SQL data

using the standard JDBC types. In a few specialized cases, it may be

advantageous to use the Oracle extension classes that are available in the

oracle.sql

package. But, Oracle strongly recommends to use the standard

JDBC types instead of Oracle extensions, whenever possible.

Table 11-1 Default Mappings Between SQL Types and Java Types

SQL Data Types JDBC Type Codes Standard Java Types Oracle Extension Java

Types

CHAR java.sql.Types.CHAR java.lang.String oracle.sql.CHAR

VARCHAR2 java.sql.Types.VARCHAR java.lang.String oracle.sql.CHAR

LONG java.sql.Types.LONGVARCHAR java.lang.String oracle.sql.CHAR

NUMBER java.sql.Types.NUMERIC java.math.BigDecimal oracle.sql.NUMBER

NUMBER java.sql.Types.DECIMAL java.math.BigDecimal oracle.sql.NUMBER

NUMBER java.sql.Types.BIT boolean oracle.sql.NUMBER

NUMBER java.sql.Types.TINYINT byte oracle.sql.NUMBER

NUMBER java.sql.Types.SMALLINT short oracle.sql.NUMBER

NUMBER java.sql.Types.INTEGER int oracle.sql.NUMBER

NUMBER java.sql.Types.BIGINT long oracle.sql.NUMBER

NUMBER java.sql.Types.REAL float oracle.sql.NUMBER

NUMBER java.sql.Types.FLOAT double oracle.sql.NUMBER

NUMBER java.sql.Types.DOUBLE double oracle.sql.NUMBER

RAW java.sql.Types.BINARY byte[] oracle.sql.RAW

RAW java.sql.Types.VARBINARY byte[] oracle.sql.RAW

LONGRAW java.sql.Types.LONGVARBINARY byte[] oracle.sql.RAW

DATE java.sql.Types.DATE java.sql.Date oracle.sql.DATE

DATE java.sql.Types.TIME java.sql.Time oracle.sql.DATE

TIMESTAMP java.sql.Types.TIMESTAMP javal.sql.Timestamp oracle.sql.TIMESTAMP

BLOB java.sql.Types.BLOB java.sql.Blob oracle.jdbc.OracleBlo

CLOB java.sql.Types.CLOB java.sql.Clob oracle.jdbc.OracleClo

user-defined

object

java.sql.Types.STRUCT java.sql.Struct oracle.jdbc.OracleStr

uct

user-defined

reference

java.sql.Types.REF java.sql.Ref oracle.jdbc.OracleRef

user-defined

collection

java.sql.Types.ARRAY java.sql.Array oracle.jdbc.OracleArr

ROWID java.sql.Types.ROWID java.sql.RowId oracle.sql.ROWID

Chapter 11

Data Type Mappings

11-2

Table 11-1 (Cont.) Default Mappings Between SQL Types and Java Types

SQL Data Types JDBC Type Codes Standard Java Types Oracle Extension Java

Types

NCLOB java.sql.Types.NCLOB java.sql.NClob oracle.sql.NCLOB

NCHAR java.sql.Types.NCHAR java.lang.String oracle.sql.CHAR

BFILE oracle.jdbc.OracleTypes.BFILE

(ORACLE EXTENSION)

oracle.sql.BFILE

REF CURSOR oracle.jdbc.OracleTypes.CURSO

(ORACLE EXTENSION)

java.sql.ResultSet oracle.jdbc.OracleRes

ultSet

TIMESTAMP oracle.jdbc.OracleTypes.TIMES

TAMP

(ORACLE EXTENSION)

java.sql.Timestamp oracle.sql.TIMESTAMP

TIMESTAMP WITH

TIME ZONE

oracle.jdbc.OracleTypes.TIMES

TAMPTZ

(ORACLE EXTENSION)

java.sql.Timestamp oracle.sql.TIMESTAMPT

TIMESTAMP WITH

LOCAL TIME

ZONE

oracle.jdbc.OracleTypes.TIMES

TAMPLTZ

(ORACLE EXTENSION)

java.sql.Timestamp oracle.sql.TIMESTAMPL

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.BLOB

class is deprecated and replaced with the

oracle.jdbc.OracleBlob

interface.

Starting from Oracle Database 12c Release 1, the

oracle.sql.CLOB

class is deprecated and is replaced with the

oracle.jdbc.OracleClob

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.STRUCT

class is deprecated and replaced with the

oracle.jdbc.OracleStruct

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.REF

class is deprecated and replaced with the

oracle.jdbc.OracleRef

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.ARRAY

class is deprecated and replaced with the

oracle.jdbc.OracleArray

interface.

Note:

For database versions, such as 8.1.7, which do not support the

TIMESTAMP

data

type,

TIMESTAMP

is mapped to

DATE

Related Topics

• Standard Types Versus Oracle Types

• Supported SQL-JDBC Data Type Mappings

11.1.2 Notes Regarding Mappings

This section provides further details regarding mappings for

NUMBER

and user-defined types.

Chapter 11

Data Type Mappings

11-3

NUMBER Types

For the different type codes that an Oracle

NUMBER

value can correspond to, call the

getter routine that is appropriate for the size of the data for mapping to work properly.

For example, call

getByte

to get a Java

tinyint

value for an item x, where -128 < x <

128.

User-Defined Types

User-defined types, such as objects, object references, and collections, map by default

to weak Java types, such as

java.sql.Struct

, but alternatively can map to strongly

typed custom Java classes. Custom Java classes can implement one of two

interfaces:

• The standard

java.sql.SQLData

• The Oracle-specific

oracle.jdbc.OracleData

Related Topics

• About Mapping Oracle Objects

• About Creating and Using Custom Object Classes for Oracle Objects

11.2 Data Conversion Considerations

When JDBC programs retrieve SQL data into Java, you can use standard Java types,

or you can use types of the

oracle.sql

package. This section covers the following

topics:

• Standard Types Versus Oracle Types

• About Converting SQL NULL Data

• About Testing for NULLs

11.2.1 Standard Types Versus Oracle Types

The Oracle data types in

oracle.sql

store data in the same bit format as used by the

database. In versions of the Oracle JDBC drivers prior to Oracle Database 10g, the

Oracle data types were generally more efficient. Starting from Oracle Database 10g,

the JDBC drivers were substantially updated. As a result, in most cases the standard

Java types are preferred to the data types in

oracle.sql.*

. In particular,

java.lang.String

is much more efficient than

oracle.sql.CHAR

In general, Oracle recommends that you use the Java standard types. The exceptions

to this are:

• Use the

oracle.jdbc.OracleData

rather than the

java.sql.SqlData

if the

OracleData

functionality better suits your needs.

• Use

oracle.sql.NUMBER

rather than

java.lang.Double

if you need to retain the

exact values of floating point numbers. Oracle

NUMBER

is a decimal representation

and Java

Double

and

Float

are binary representations. Conversion from one

format to the other can result in slight variations in the actual value represented.

Additionally, the range of values that can be represented using the two formats is

different.

Chapter 11

Data Conversion Considerations

11-4

Use

oracle.sql.NUMBER

rather than

java.math.BigDecimal

when performance is critical

and you are not manipulating the values, just reading and writing them.

• Use

oracle.sql.DATE

oracle.sql.TIMESTAMP

if you are using a JDK version earlier

than JDK 6. Use

java.sql.Date

java.sql.Timestamp

if you are using JDK 6 or a later

version.

Note:

Due to a bug in all versions of Java prior to JDK 6, construction of

java.lang.Date

and

java.lang.Timestamp

objects is slow, especially in

multithreaded environments. This bug is fixed in JDK 6.

• Use

oracle.sql.CHAR

only when you have data from some external source, which has

been represented in an Oracle character set encoding. In all other cases, you should use

java.lang.String

•

STRUCT

ARRAY

BLOB

CLOB

REF

, and

ROWID

are all the implementation classes of the

corresponding JDBC standard interface types. So, there is no benefit of using the Oracle

extension types as they are identical to the JDBC standard types.

•

BFILE

TIMESTAMPTZ

, and

TIMESTAMPLTZ

have no representation in the JDBC standard.

You must use these Oracle extensions.

• In all other cases, you should use the standard JDBC type rather than the Oracle

extensions.

Note:

If you convert an

oracle.sql

data type to a Java standard data type, then the

benefits of using the

oracle.sql

data type are lost.

11.2.2 About Converting SQL NULL Data

Java represents a SQL

NULL

datum by the Java value

null

. Java data types fall into two

categories: primitive types, such as

byte

int

, and

float

, and object types, such as class

instances. The primitive types cannot represent

null

. Instead, they store

null

as the value

zero, as defined by the JDBC specification. This can lead to ambiguity when you try to

interpret your results.

In contrast, Java object types can represent

null

. The Java language defines an object

container type corresponding to every primitive type that can represent

null

. The object

container types must be used as the targets for SQL data to detect SQL

NULL

without

ambiguity.

11.2.3 About Testing for NULLs

You cannot use a relational operator to compare

NULL

values with each other or with other

values. For example, the following

SELECT

statement does not return any row even if the

COMMISSION_PCT

column contains one or more

NULL

values.

Chapter 11

Data Conversion Considerations

11-5

PreparedStatement pstmt = conn.prepareStatement(

"SELECT * FROM EMPLOYEES WHERE COMMISSION_PCT = ?");

pstmt.setNull(1, java.sql.Types.VARCHAR);

The next example shows how to compare values for equality when some return values

might be

NULL

. The following code returns all the

FIRST_NAME

from the

EMPLOYEES

table

that are

NULL

, if there is no value of 205 for

COMM

PreparedStatement pstmt = conn.prepareStatement("SELECT FIRST_NAME FROM

EMPLOYEES

WHERE COMMISSION_PCT =? OR ((COMM IS NULL) AND (? IS NULL))");

pstmt.setBigDecimal(1, new BigDecimal(205));

pstmt.setNull(2, java.sql.Types.VARCHAR);

11.3 Result Set and Statement Extensions

The

Statement

object returns a

java.sql.ResultSet

. If you want to apply only

standard JDBC methods to the object, then keep it as a

ResultSet

type. However, if

you want to use the Oracle extensions on the object, then you must cast it to

OracleResultSet

. All of the Oracle Result Set extensions are in the

oracle.jdbc.OracleResultSet

interface and all the

Statement

extensions are in the

oracle.jdbc.OracleStatement

interface.

For example, assuming you have a standard

Statement

object

stmt

, do the following if

you want to use only standard JDBC

ResultSet

methods:

ResultSet rs = stmt.executeQuery("SELECT * FROM employees");

If you need the extended functionality provided by the Oracle extensions to JDBC, you

can select the results into a standard

ResultSet

variable and then cast that variable to

OracleResultSet

later.

Key extensions to the result set and statement classes include the

getOracleObject

and

setOracleObject

methods, used to access and manipulate data in

oracle.sql.*

formats.

11.4 Comparison of Oracle get and set Methods to Standard

JDBC

This section describes

get

and

set

methods, particularly the JDBC standard

getObject

and

setObject

methods and the Oracle-specific

getOracleObject

and

setOracleObject

methods, and how to access data in

oracle.sql.*

format compared

with Java format.

You can use the standard

getXXX

methods for all Oracle SQL types.

This section covers the following topics:

• Standard getObject Method

• Oracle getOracleObject Method

• Summary of getObject and getOracleObject Return Types

• Other getXXX Methods

• Data Types For Returned Objects from getObject and getXXX

Chapter 11

Result Set and Statement Extensions

11-6

• The setObject and setOracleObject Methods

• Other setXXX Methods

Note:

You cannot qualify a column name with a table name and pass it as a parameter to

the

getXXX

method. For example:

ResultSet rset = stmt.executeQuery("SELECT employees.department_id,

department.department_id FROM employees, department");

rset.getInt("employees.department_id");

The

getInt

method in the preceding code will throw an exception. To uniquely

identify the columns in the

getXXX

method, you can either use column index or

specify column aliases in the query and use these aliases in the

getXXX

method.

11.4.1 Standard getObject Method

The standard

getObject

method of a result set or callable statement has a return type of

java.lang.Object

. The class of the object returned is based on its SQL type, as follows:

• For SQL data types that are not Oracle-specific, the

getObject

method returns the

default Java type corresponding to the SQL type of the column, following the mapping in

the JDBC specification.

• For Oracle-specific data types,

getObject

returns an object of the appropriate

oracle.sql.*

class, such as

oracle.sql.ROWID

• For Oracle database objects,

getObject

returns a Java object of the class specified in

your type map. Type maps specify a mapping from database named types to Java

classes. The

getObject(parameter_index)

method uses the default type map of the

connection. The

getObject(parameter_index, map)

enables you to pass in a type map.

If the type map does not provide a mapping for a particular Oracle object, then

getObject

returns an

oracle.sql.OracleStruct

object.

11.4.2 Oracle getOracleObject Method

If you want to retrieve data from a result set or callable statement as an

oracle.sql.*

object,

then you must follow a special process. For an

OracleResultSet

object, you must cast the

Result Set to

oracle.jdbc.OracleResultSet

and then call

getOracleObject

instead of

getObject

. The same applies to

CallableStatement

and

oracle.jdbc.OracleCallableStatement

The return type of

getOracleObject

oracle.sql.Datum

. The actual returned object is an

instance of the appropriate

oracle.sql.*

class. The method signature is:

public oracle.sql.Datum getOracleObject(int

arameter_index)

When you retrieve data into a

Datum

variable, you can use the standard Java

instanceof

operator to determine which

oracle.sql.*

type it really is.

Chapter 11

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11-7

Example: Using getOracleObject with a Result Set

The following example creates a table that contains a column of

CHAR

data and a

column containing a

BFILE

locator. A

SELECT

statement retrieves the contents of the

table as a result set. The

getOracleObject

then retrieves the

CHAR

data into the

char_datum

variable and the

BFILE

locator into the

bfile_datum

variable. Note that

because

getOracleObject

returns a

Datum

object, the return values must be cast to

CHAR

and

BFILE

, respectively.

stmt.execute ("CREATE TABLE bfile_table (x VARCHAR2 (30), b BFILE)");

stmt.execute

("INSERT INTO bfile_table VALUES ('one', BFILENAME ('TEST_DIR', 'file1'))");

ResultSet rset = stmt.executeQuery ("SELECT * FROM bfile_table");

while (rset.next ())

{

CHAR char_datum = (CHAR) ((OracleResultSet)rset).getOracleObject (1);

BFILE bfile_datum = (BFILE) ((OracleResultSet)rset).getOracleObject (2);

...

}

Example: Using getOracleObject in a Callable Statement

The following example prepares a call to the procedure

myGetDate

, which associates a

character string with a date. The program passes "

HR"

to the prepared call and

registers the

DATE

type as an output parameter. After the call is run,

getOracleObject

retrieves the date associated with

"HR"

. Note that because

getOracleObject

returns a

Datum

object, the results are cast to

DATE

OracleCallableStatement cstmt = (OracleCallableStatement)conn.prepareCall

("begin myGetDate (?, ?); end;");

cstmt.setString (1, "HR");

cstmt.registerOutParameter (2, Types.DATE);

cstmt.execute ();

DATE date = (DATE) ((OracleCallableStatement)cstmt).getOracleObject (2);

...

11.4.3 Summary of getObject and getOracleObject Return Types

The following table lists the underlying return types for the

getObject

and

getOracleObject

methods for each Oracle SQL type.

Keep in mind the following when you use these methods:

•

getObject

always returns data into a

java.lang.Object

instance

•

getOracleObject

always returns data into an

oracle.sql.Datum

instance

You must cast the returned object to use any special functionality.

Chapter 11

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11-8

Table 11-2 getObject and getOracleObject Return Types

Oracle SQL Type getObject Underlying Return Type getOracleObject Underlying Return

Type

CHAR String oracle.sql.CHAR

VARCHAR2 String oracle.sql.CHAR

NCHAR String oracle.sql.CHAR

LONG String oracle.sql.CHAR

NUMBER java.math.BigDecimal oracle.sql.NUMBER

RAW byte[] oracle.sql.RAW

LONGRAW byte[] oracle.sql.RAW

DATE java.sql.Date oracle.sql.DATE

TIMESTAMP java.sql.Timestamp

oracle.sql.TIMESTAMP

TIMESTAMP WITH

TIME ZONE

oracle.sql.TIMESTAMPTZ oracle.sql.TIMESTAMPTZ

TIMESTAMP WITH

LOCAL TIME ZONE

oracle.sql.TIMESTAMPLTZ oracle.sql.TIMESTAMPLTZ

BINARY_FLOAT java.lang.Float oracle.sql.BINARY_FLOAT

BINARY_DOUBLE java.lang.Double oracle.sql.BINARY_DOUBLE

INTERVAL DAY TO

SECOND

oracle.sql.INTERVALDS oracle.sql.INTERVALDS

INTERVAL YEAR

TO MONTH

oracle.sql.INTERVALYM oracle.sql.INTERVALYM

ROWID oracle.sql.ROWID oracle.sql.ROWID

REF CURSOR java.sql.ResultSet

(not supported)

BLOB oracle.jdbc.OracleBlob

oracle.jdbc.OracleBlob

CLOB oracle.jdbc.OracleClob

oracle.jdbc.OracleClob

NCLOB java.sql.NClob oracle.sql.NCLOB

BFILE oracle.sql.BFILE oracle.sql.BFILE

Oracle object class specified in type map

oracle.sql.OracleStruct

(if no

type map entry)

oracle.jdbc.OracleStruct

Oracle object

reference

oracle.jdbc.OracleRef

collection (varray or

nested table)

oracle.jdbc.OracleArray

oracle.sql.ARRAY

ResultSet.getObject

returns

java.sql.Timestamp

only if the

oracle.jdbc.J2EE13Compliant

connection property is set to

TRUE

, else the method returns

oracle.sql.TIMESTAMP

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.BLOB

class is deprecated and replaced

with the

oracle.jdbc.OracleBlob

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.CLOB

class is deprecated and replaced

with the

oracle.jdbc.OracleClob

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.STRUCT

class is deprecated and

replaced with the

oracle.jdbc.OracleStruct

interface.

Chapter 11

Comparison of Oracle get and set Methods to Standard JDBC

11-9

Starting from Oracle Database 12c Release 1, the

oracle.sql.REF

class is deprecated and is

replaced with the

oracle.jdbc.OracleRef

interface.

Starting from Oracle Database 12c Release 1, the

oracle.sql.ARRAY

class is deprecated and

replaced with the

oracle.jdbc.OracleArray

interface.

Note:

The

ResultSet.getObject

method returns

java.sql.Timestamp

for the

TIMESTAMP

SQL type, only when the connection property

oracle.jdbc.J2EE13Compliant

is set to

TRUE

. This property has to be set

when the connection is obtained. If this connection property is not set or if it

is set after the connection is obtained, then the

ResultSet.getObject

method returns

oracle.sql.TIMESTAMP

for the

TIMESTAMP

SQL type.

The

oracle.jdbc.J2EE13Compliant

connection property can also be set

without changing the code in the following ways:

• Including the

ojdbc6dms.jar

ojdbc7dms.jar

files in the

CLASSPATH

These files set

oracle.jdbc.J2EE13Compliant

TRUE

by default. These

are specific to the Oracle Application Server release and are not

available as part of the general JDBC release. They are located

$ORACLE_HOME/jdbc/lib

• Setting the system property by calling the

java

command with the flag

Doracle.jdbc.J2EE13Compliant=true

. For example,

java -Doracle.jdbc.J2EE13Compliant=true ...

When the

J2EE13Compliant

is set to

TRUE

the action is as in Table B-3 of the

JDBC specification.

Related Topics

• Supported SQL-JDBC Data Type Mappings

11.4.4 Other getXXX Methods

Standard JDBC provides a

getXXX

for each standard Java type, such as

getByte

getInt

getFloat

, and so on. Each of these returns exactly what the method name

implies.

In addition, the

OracleResultSet

and

OracleCallableStatement

interfaces provide a

full complement of

getXXX

methods corresponding to all the

oracle.sql.*

types. Each

getXXX

method returns an

oracle.sql.XXX

object. For example,

getROWID

returns an

oracle.sql.ROWID

object.

There is no performance advantage in using the specific

getXXX

methods. However,

they do save you the trouble of casting, because the return type is specific to the

object being returned.

This section covers the following topics:

• Return Types of getXXX Methods

• Special Notes about getXXX Methods

Chapter 11

Comparison of Oracle get and set Methods to Standard JDBC

11-10

11.4.4.1 Return Types of getXXX Methods

Refer to the JDBC Javadoc to know the return types for each

getXXX

method and also which

are Oracle extensions under Java Development Kit (JDK) 6. You must cast the returned

object to

OracleResultSet

OracleCallableStatement

to use methods that are Oracle

extensions.

11.4.4.2 Special Notes about getXXX Methods

This section provides additional details about some

getXXX

methods.

getBigDecimal

JDBC 2.0 simplified method signatures for the

getBigDecimal

method. The previous input

signatures were:

(int columnIndex, int scale) or (String columnName, int scale)

The simplified input signature is:

(int columnIndex) or (String columnName)

The

scale

parameter, used to specify the number of digits to the right of the decimal, is no

longer necessary. The Oracle JDBC drivers retrieve numeric values with full precision.

getBoolean

Because there is no

BOOLEAN

database type, when you use

getBoolean

a data type

conversion always occurs. The

getBoolean

method is supported only for numeric columns.

When applied to these columns,

getBoolean

interprets any zero value as

false

and any

other value as

true

. When applied to any other sort of column,

getBoolean

raises the

exception

java.lang.NumberFormatException

11.4.5 Data Types For Returned Objects from getObject and getXXX

The return type of

getObject

java.lang.Object

. The returned value is an instance of a

subclass of

java.lang.Object

. Similarly, the return type of

getOracleObject

oracle.sql.Datum

, and the class of the returned value is a subclass of

oracle.sql.Datum

You typically cast the returned object to the appropriate class to use particular methods and

functionality of that class.

In addition, you have the option of using a specific

getXXX

method instead of the generic

getObject

getOracleObject

methods. The

getXXX

methods enable you to avoid casting,

because the return type of

getXXX

corresponds to the type of object returned. For example,

the return type of

getCLOB

oracle.sql.CLOB

, as opposed to

java.lang.Object

Example of Casting Return Values

This example assumes that you have fetched data of the

NUMBER

type as the first column of a

result set. Because you want to manipulate the

NUMBER

data without losing precision, cast

your result set to

OracleResultSet

and use

getOracleObject

to return the

NUMBER

data in

oracle.sql.*

format. If you do not cast your result set, then you have to use

getObject

which returns your numeric data into a Java

Float

and loses some of the precision of your

SQL data.

Chapter 11

Comparison of Oracle get and set Methods to Standard JDBC

11-11

The

getOracleObject

method returns an

oracle.sql.NUMBER

object into an

oracle.sql.Datum

return variable unless you cast the output. Cast the

getOracleObject

output to

oracle.sql.NUMBER

if you want to use a

NUMBER

return

variable and any of the special functionality of that class.

NUMBER x = (NUMBER)ors.getOracleObject(1);

11.4.6 The setObject and setOracleObject Methods

Just as there is a standard

getObject

and Oracle-specific

getOracleObject

in result

sets and callable statements, there are also standard

setObject

and Oracle-specific

setOracleObject

methods in

OraclePreparedStatement

and

OracleCallableStatement

. The

setOracleObject

methods take

oracle.sql.*

input

parameters.

To bind standard Java types to a prepared statement or callable statement, use the

setObject

method, which takes a

java.lang.Object

as input. The

setObject

method

does support a few of the

oracle.sql.*

types. However, the method has been

implemented so that you can enter instances of the

oracle.sql.*

classes that

correspond to the following JDBC standard types:

Blob

Clob

Struct

Ref

, and

Array

To bind

oracle.sql.*

types to a prepared statement or callable statement, use the

setOracleObject

method, which takes a subclass of

oracle.sql.Datum

as input. To

use

setOracleObject

, you must cast your prepared statement or callable statement to

OraclePreparedStatement

OracleCallableStatement

Example of Using setObject and setOracleObject

For a prepared statement, the

setOracleObject

method binds the

oracle.sql.CHAR

data represented by the

charVal

variable to the prepared statement. To bind the

oracle.sql.*

data, the prepared statement must be cast to

OraclePreparedStatement

. Similarly, the

setObject

method binds the Java

String

data represented by the variable

strVal

PreparedStatement ps= conn.prepareStatement("

ext_of_prepared_statement");

((OraclePreparedStatement)ps).setOracleObject(1,charVal);

ps.setObject(2,strVal);

11.4.7 Other setXXX Methods

As with the

getXXX

methods, there are several specific

setXXX

methods. Standard

setXXX

methods are provided for binding standard Java types, and Oracle-specific

setXXX

methods are provided for binding Oracle-specific types.

Similarly, there are two forms of the

setNull

method:

•

void setNull(int parameterIndex, int sqlType)

This is specified in the standard

java.sql.PreparedStatement

interface. This

signature takes a parameter index and a SQL type code defined by the

java.sql.Types

oracle.jdbc.OracleTypes

class. Use this signature to set an

object other than a

REF

ARRAY

, or

STRUCT

NULL

•

void setNull(int parameterIndex

int sqlType, String sql_type_name

)

Chapter 11

Comparison of Oracle get and set Methods to Standard JDBC

11-12

With JDBC 2.0, this signature is also specified in the standard

java.sql.PreparedStatement

interface. This method takes a SQL type name in addition

to a parameter index and a SQL type code. Use this method when the SQL type code is

java.sql.Types.REF

ARRAY

, or

STRUCT

. If the type code is other than

REF

ARRAY

, or

STRUCT

, then the given SQL type name is ignored.

Similarly, the

registerOutParameter

method has a signature for use with

REF

ARRAY

, or

STRUCT

data:

void registerOutParameter

(int parameterIndex, int sqlType, String sql_type_name)

Binding Oracle-specific types using the appropriate

setXXX

methods, instead of the methods

used for binding standard Java types, may offer some performance advantage.

This section covers the following topics:

• Input Data Binding

• Method setFixedCHAR for Binding CHAR Data into WHERE Clauses

11.4.7.1 Input Data Binding

There are three way to bind data for input:

• Direct binding where the data itself is placed in a bind buffer

• Stream binding where the data is streamed

• LOB binding where a temporary lob is created, the data placed in the LOB using the LOB

APIs, and the bytes of the LOB locator are placed in the bind buffer

The three kinds of binding have some differences in performance and have an impact on

batching. Direct binding is fast and batching is fine. Stream binding is slower, may require

multiple round trips, and turns batching off. LOB binding is very slow and requires many

round trips. Batching works, but might be a bad idea. They also have different size limits,

depending on the type of the SQL statement.

For SQL parameters, the length of standard parameter types, such as

RAW

and

VARCHAR2

, is

fixed by the size of the target column. For PL/SQL parameters, the size is limited to a fixed

number of bytes, which is 32766.

In Oracle Database 10g release 2, certain changes were made to the

setString

setCharacterStream

setAsciiStream

setBytes

, and

setBinaryStream

methods of

PreparedStatement

. The original behavior of these APIs were:

•

setString

: Direct bind of characters

•

setCharacterStream

: Stream bind of characters

•

setAsciiStream

: Stream bind of bytes

•

setBytes

: Direct bind of bytes

•

setBinaryStream

: Stream bind of bytes

Starting from Oracle Database 10g Release 2, automatic switching between binding modes,

based on the data size and on the type of the SQL statement is provided.

setBytes and setBinaryStream

For SQL, direct bind is used for size up to 2000 and stream bind for larger.

Chapter 11

Comparison of Oracle get and set Methods to Standard JDBC

11-13

For PL/SQL direct bind is used for size up to 32766 and LOB bind is used for larger.

setString, setCharacterStream, and setAsciiStream

For SQL, direct bind is used up to 32766 Java characters and stream bind is used for

larger. This is independent of character set.

For PL/SQL, you must be careful about the byte size of the character data in the

database character set or the national character set depending on the setting of the

form of use parameter. Direct bind is used for data where the byte length is less than

32766 and LOB bind is used for larger.

For fixed length character sets, multiply the length of the Java character data by the

fixed character size in bytes and compare that to the restrictive values. For variable

length character sets, there are three cases based on the Java character length, as

follows:

• If character length is less than 32766 divided by the maximum character size, then

direct bind is used.

• If character length is greater than 32766 divided by the minimum character size,

then LOB bind is used.

• If character length is in between and if the actual length of the converted bytes is

less than 32766, then direct bind is used, else LOB bind is used.

Note:

When a PL/SQL procedure is embedded in a SQL statement, the binding

action is different.

The server-side internal driver has the following additional limitations:

•

setString

setCharacterStream

, and

setASCIIStream

APIs are not supported for

SQL CLOB columns when the data size in characters is over 32767 bytes

•

setBytes

and

setBinaryStream

APIs are not supported for SQL BLOB columns

when the data size is over 32767 bytes

Note:

Do not use these APIs with the server-side internal driver, without careful

checking of the data size in client code.

Related Topics

• Data Interface for LOBs

The data interface for LOBs includes a set of Java and OCI APIs that are

extended to work with LOB data types.

Chapter 11

Comparison of Oracle get and set Methods to Standard JDBC

11-14

See Also:

JDBC Release Notes for further discussion and possible workarounds

11.4.7.2 Method setFixedCHAR for Binding CHAR Data into WHERE Clauses

CHAR

data in the database is padded to the column width. This leads to a limitation in using

the

setCHAR

method to bind character data into the

WHERE

clause of a

SELECT

statement. The

character data in the

WHERE

clause must also be padded to the column width to produce a

match in the

SELECT

statement. This is especially troublesome if you do not know the column

width.

To remedy this, Oracle has added the

setFixedCHAR

method to the

OraclePreparedStatement

class. This method runs a non-padded comparison.

Note:

• Remember to cast your prepared statement object to

OraclePreparedStatement

to use the

setFixedCHAR

method.

• There is no need to use

setFixedCHAR

for an

INSERT

statement. The database

always automatically pads the data to the column width as it inserts it.

Example

The following example demonstrates the difference between the

setCHAR

and

setFixedCHAR

methods.

/* Schema is :

create table my_table (col1 char(10));

insert into my_table values ('JDBC');

PreparedStatement pstmt = conn.prepareStatement

("select count(*) from my_table where col1 = ?");

pstmt.setString (1, "JDBC"); // Set the Bind Value

runQuery (pstmt); // This will print " No of rows are 0"

CHAR ch = new CHAR("JDBC ", null);

((OraclePreparedStatement)pstmt).setCHAR(1, ch); // Pad it to 10 bytes

runQuery (pstmt); // This will print "No of rows are 1"

((OraclePreparedStatement)pstmt).setFixedCHAR(1, "JDBC");

runQuery (pstmt); // This will print "No of rows are 1"

void runQuery (PreparedStatement ps)

{

// Run the Query

ResultSet rs = pstmt.executeQuery ();

while (rs.next())

System.out.println("No of rows are " + rs.getInt(1));

Chapter 11

Comparison of Oracle get and set Methods to Standard JDBC

11-15

rs.close();

rs = null;

}

11.5 Using Result Set Metadata Extensions

The

oracle.jdbc.OracleResultSetMetaData

interface is JDBC 2.0-compliant but

does not implement the

getSchemaName

and

getTableName

methods because Oracle

Database does not make this feasible.

The following code snippet uses several of the methods in the

OracleResultSetMetadata

interface to retrieve the number of columns from the

EMPLOYEES

table and the numerical type and SQL type name of each column:

DatabaseMetaData dbmd = conn.getMetaData();

ResultSet rset = dbmd.getTables("", "HR", "EMPLOYEES", null);

while (rset.next())

{

OracleResultSetMetaData orsmd = ((OracleResultSet)rset).getMetaData();

int numColumns = orsmd.getColumnCount();

System.out.println("Num of columns = " + numColumns);

for (int i=0; i<numColumns; i++)

{

System.out.print ("Column Name=" + orsmd.getColumnName (i+1));

System.out.print (" Type=" + orsmd.getColumnType (i + 1) );

System.out.println (" Type Name=" + orsmd.getColumnTypeName (i + 1));

}

The program returns the following output:

Num of columns = 5

Column Name=TABLE_CAT Type=12 Type Name=VARCHAR2

Column Name=TABLE_SCHEM Type=12 Type Name=VARCHAR2

Column Name=TABLE_NAME Type=12 Type Name=VARCHAR2

Column Name=TABLE_TYPE Type=12 Type Name=VARCHAR2

Column Name=TABLE_REMARKS Type=12 Type Name=VARCHAR2

11.6 About Using SQL CALL and CALL INTO Statements

You can use the CALL statement to execute a routine from within SQL in the following

two ways:

Note:

A routine is a procedure or a function that is standalone or is defined within a

type or package. You must have

EXECUTE

privilege on the standalone routine

or on the type or package in which the routine is defined.

• By issuing a call to the routine itself by name or by using the

routine_clause

• By using an

object_access_expression

inside the type of an expression

Chapter 11

Using Result Set Metadata Extensions

11-16

You can specify one or more arguments to the routine, if the routine takes arguments. You

can use positional, named, or mixed notation for argument.

CALL INTO Statement

The

INTO

clause applies only to calls to functions. You can use the following types of

variables with this clause:

• Host variable

• Indicator variable

See Also:

Oracle Database SQL Language Reference for more information

PL/SQL Blocks

The basic unit in PL/SQL is a block. All PL/SQL programs are made up of blocks, which can

be nested within each other. A PL/SQL block has three parts: a declarative part, an

executable part, and an exception-handling part. You get the following advantages by using

PL/SQL blocks in your application:

• Better performance

• Higher productivity

• Full portability

• Tight integration with Oracle

• Tight security

Chapter 11

About Using SQL CALL and CALL INTO Statements

11-17

Java Streams in JDBC

This chapter describes how the Oracle Java Database Connectivity (JDBC) drivers handle

Java streams for several data types. Data streams enable you to read

LONG

column data of

up to 2 gigabytes (GB).

This chapter covers the following topics:

• Overview of Java Streams

• About Streaming LONG or LONG RAW Columns

• About Streaming CHAR_ VARCHAR_ or RAW Columns

• About Streaming LOBs and External Files

• Relation Between Data Streaming and Multiple Columns

• Relation Between Streaming and Row Prefetching

• Closing a Stream

• Notes and Precautions on Streams

12.1 Overview of Java Streams

Oracle JDBC drivers support the manipulation of data streams in either direction between

server and client. The drivers support all stream conversions: binary, ASCII, and Unicode.

Following is a brief description of each type of stream:

• Binary

Used for

RAW

bytes of data, and corresponds to the

getBinaryStream

method

• ASCII

Used for ASCII bytes in ISO-Latin-1 encoding, and corresponds to the

getAsciiStream

method

• Unicode

Used for Unicode bytes with the

UTF-16

encoding, and corresponds to the

getUnicodeStream

method

The

getBinaryStream

getAsciiStream

, and

getUnicodeStream

methods return the bytes of

data in an

InputStream

object.

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

CONNECTION_PROPERTY_STREAM_CHUNK_SIZE

is deprecated and the driver does not

use it internally for setting the stream chunk size.

12-1

See Also:

Working with LOBs and BFILEs

12.2 About Streaming LONG or LONG RAW Columns

This section covers the following topics:

• Overview of Streaming LONG or LONG RAW Columns

• LONG RAW Data Conversions

• LONG Data Conversions

• Examples:Streaming LONG RAW Data

• About Avoiding Streaming for LONG or LONG RAW

12.2.1 Overview of Streaming LONG or LONG RAW Columns

When a query selects one or more

LONG

RAW

columns, the JDBC driver

transfers these columns to the client in streaming mode. In streaming mode, the JDBC

driver does not read the column data from the network for

LONG

LONG RAW

columns,

until required. The column data remains in the network communications channel until

your code calls a

getXXX

method to read the column data. Even after the call, the

column data is read only as needed to populate return value from the getXXX call.

Because the column data remains in the communications channel, the streaming

mode interferes with all other use of the connection. Any use of the connection, other

than reading the column data, will discard the column data from the channel. While the

streaming mode makes efficient use of memory and minimizes network round trips, it

interferes with many other database operations.

Note:

Oracle recommends avoiding

LONG

and

LONG RAW

columns. Use

LOB

instead.

To access the data in a

LONG

column, you can get the column as a Java

InputStream

object and use the

read

method of the

InputStream

object. As an alternative, you can

get the data as a

String

byte

array. In this case, the driver will do the streaming for

you.

You can get

LONG

and

LONG

RAW

data with any of the three stream types. The driver

performs conversions for you, depending on the character set of the database and the

driver.

Chapter 12

About Streaming LONG or LONG RAW Columns

12-2

Note:

Do not create tables with

LONG

columns. Use large object (LOB) columns,

CLOB

NCLOB

, and

BLOB

, instead.

LONG

columns are supported only for backward

compatibility. Oracle recommends that you convert existing

LONG

columns to

LOB

columns.

LOB

columns are subject to far fewer restrictions than

LONG

columns.

12.2.2 LONG RAW Data Conversions

A call to

getBinaryStream

returns

RAW

data. A call to

getAsciiStream

converts the

RAW

data

to hexadecimal and returns the ASCII representation. A call to

getUnicodeStream

converts

the

RAW

data to hexadecimal and returns the Unicode characters.

12.2.3 LONG Data Conversions

When you get

LONG

data with

getAsciiStream

, the drivers assume that the underlying data in

the database uses an

US7ASCII

WE8ISO8859P1

character set. If the assumption is true, then

the drivers return bytes corresponding to ASCII characters. If the database is not using an

US7ASCII

WE8ISO8859P1

character set, a call to

getAsciiStream

returns meaningless

information.

When you get

LONG

data with

getUnicodeStream

, you get a stream of Unicode characters in

the

UTF-16

encoding. This applies to all underlying database character sets that Oracle

supports.

When you get

LONG

data with

getBinaryStream

, there are two possible cases:

• If the driver is JDBC OCI and the client character set is not

US7ASCII

WE8ISO8859P1

then a call to

getBinaryStream

returns

UTF-8

. If the client character set is

US7ASCII

WE8ISO8859P1

, then the call returns a

US7ASCII

stream of bytes.

• If the driver is JDBC Thin and the database character set is not

US7ASCII

WE8ISO8859P1

, then a call to

getBinaryStream

returns

UTF-8

. If the server-side character

set is

US7ASCII

WE8ISO8859P1

, then the call returns a

US7ASCII

stream of bytes.

Note:

Receiving

LONG

RAW

columns as a stream requires you to pay special

attention to the order in which you retrieve columns from the database.

The following table summarizes

LONG

and

LONG

RAW

data conversions for each stream type.

Chapter 12

About Streaming LONG or LONG RAW Columns

12-3

Table 12-1 LONG and LONG RAW Data Conversions

Data

type

BinaryStream AsciiStream UnicodeStrea

LONG

Bytes representing characters in

Unicode

UTF-8

. The bytes can

represent characters in

US7ASCII

WE8ISO8859P1

if the database

character set is

US7ASCII

WE8ISO8859P1

Bytes representing

characters in ISO-Latin-1

(

WE8ISO8859P1

) encoding

Bytes

representing

characters in

Unicode

UTF-16

encoding

LONG

RAW

unchanged data ASCII representation of

hexadecimal bytes

Unicode

representation

of hexadecimal

bytes

Related Topics

• Globalization Support

• Relation Between Data Streaming and Multiple Columns

12.2.4 Examples:Streaming LONG RAW Data

One of the features of a

getXXXStream

method is that it enables you to fetch data

incrementally. In contrast,

getBytes

fetches all the data in one call. This section

contains two examples of getting a stream of binary data. The first version uses the

getBinaryStream

method to obtain

LONG

RAW

data, and the second version uses the

getBytes

method.

Getting a LONG RAW Data Column with getBinaryStream

This example writes the contents of a

LONG

RAW

column to a file on the local file system.

In this case, the driver fetches the data incrementally.

The following code creates the table that stores a column of

LONG

RAW

data associated

with the name LESLIE:

-- SQL code:

create table streamexample (NAME varchar2 (256), GIFDATA long raw);

insert into streamexample values ('LESLIE', '00010203040506070809');

The following Java code snippet writes the data from the

LONG

RAW

column into a file

called

leslie.gif:

ResultSet rset = stmt.executeQuery

("select GIFDATA from streamexample where NAME='LESLIE'");

// get first row

if (rset.next())

{

// Get the GIF data as a stream from Oracle to the client

InputStream gif_data = rset.getBinaryStream (1);

try

{

FileOutputStream file = null;

file = new FileOutputStream ("leslie.gif");

Chapter 12

About Streaming LONG or LONG RAW Columns

12-4

int chunk;

while ((chunk = gif_data.read()) != -1)

file.write(chunk);

}

catch (Exception e)

{

String err = e.toString();

System.out.println(err);

}

finally

{

if file != null()

file.close();

}

In this example, the

InputStream

object returned by the call to

getBinaryStream

reads the

data directly from the database connection.

Getting a LONG RAW Data Column with getBytes

This example gets the content of the

GIFDATA

column with

getBytes

instead of

getBinaryStream

. In this case, the driver fetches all the data in one call and stores it in a byte

array. The code snippet is as follows:

ResultSet rset2 = stmt.executeQuery

("select GIFDATA from streamexample where NAME='LESLIE'");

// get first row

if (rset2.next())

{

// Get the GIF data as a stream from Oracle to the client

byte[] bytes = rset2.getBytes(1);

try

{

FileOutputStream file = null;

file = new FileOutputStream ("leslie2.gif");

file.write(bytes);

}

catch (Exception e)

{

String err = e.toString();

System.out.println(err);

}

finally

{

if file != null()

file.close();

}

Because a

LONG RAW

column can contain up to 2 gigabytes of data, the

getBytes

example

can use much more memory than the

getBinaryStream

example. Use streams if you do not

know the maximum size of the data in your

LONG

LONG RAW

columns.

Chapter 12

About Streaming LONG or LONG RAW Columns

12-5

12.2.5 About Avoiding Streaming for LONG or LONG RAW

Note:

Starting from Oracle Database 12c Release 1 (12.1), this method is

deprecated.

The JDBC driver automatically streams any

LONG

and

LONG RAW

columns. However,

there may be situations where you want to avoid data streaming. For example, if you

have a very small

LONG

column, then you may want to avoid returning the data

incrementally and, instead, return the data in one call.

To avoid streaming, use the

defineColumnType

method to redefine the type of the

LONG

column. For example, if you redefine the

LONG

LONG RAW

column as

VARCHAR

VARBINARY

type, then the driver will not automatically stream the data.

If you redefine column types with

defineColumnType

, then you must declare the types

of the columns in the query. If you do not declare the types of the columns, then

executeQuery

will fail. In addition, you must cast the

Statement

object to

oracle.jdbc.OracleStatement

As an added benefit, using

defineColumnType

saves the OCI driver a database round-

trip when running the query. Without

defineColumnType

, these JDBC drivers must

request the data types of the column types. The JDBC Thin driver derives no benefit

from

defineColumnType

, because it always uses the minimum number of round-trips.

Using the example from the previous section, the

Statement

object

stmt

is cast to

OracleStatement

and the column containing

LONG RAW

data is redefined to be of the

type

VARBINARAY

. The data is not streamed. Instead, it is returned in a byte array. The

code snippet is as follows:

//cast the statement stmt to an OracleStatement

oracle.jdbc.OracleStatement ostmt =

(oracle.jdbc.OracleStatement)stmt;

//redefine the LONG column at index position 1 to VARBINARY

ostmt.defineColumnType(1, Types.VARBINARY);

// Do a query to get the images named 'LESLIE'

ResultSet rset = ostmt.executeQuery

("select GIFDATA from streamexample where NAME='LESLIE'");

// The data is not streamed here

rset.next();

byte [] bytes = rset.getBytes(1);

Chapter 12

About Streaming LONG or LONG RAW Columns

12-6

12.3 About Streaming CHAR, VARCHAR, or RAW Columns

Note:

Starting from Oracle Database 12c Release 1 (12.1), this method is deprecated..

If you use the

defineColumnType

Oracle extension to redefine a

CHAR

VARCHAR

, or

RAW

column as a

LONGVARCHAR

LONGVARBINARY

, then you can get the column as a stream. The

program will behave as if the column were actually of type

LONG

LONG RAW

. Note that there

is not much point to this, because these columns are usually short.

If you try to get a

CHAR

VARCHAR

, or

RAW

column as a data stream without redefining the

column type, then the JDBC driver will return a Java

InputStream

, but no real streaming

occurs. In the case of these data types, the JDBC driver fully fetches the data into an in-

memory buffer during a call to the

executeQuery

method or the

method. The

getXXXStream

entry points return a stream that reads data from this buffer.

12.4 About Streaming LOBs and External Files

The term large object (LOB) refers to a data item that is too large to be stored directly in a

database table. Instead, a locator is stored in the database table, which points to the location

of the actual data. External files are managed similarly. The JDBC drivers can support the

following types through the use of streams:

• Binary large object (BLOB)

For unstructured binary data

• Character large object (CLOB)

For character data

• National Character large object (NCLOB)

For national character data

• Binary file (BFILE)

For external files

LOBs and BFILEs behave differently from the other types of streaming data described in this

chapter. Instead of storing the actual data in the table, a locator is stored. The actual data can

be manipulated using this locator, including reading and writing the data as a stream. Even

when streaming, only the chunk of data (defined by a size) is streamed across the network.

By contrast, when streaming a

LONG

RAW

, the entire data is streamed across the

network.

Streaming BLOBs, CLOBs, and NCLOBs

When a query fetches one or more

BLOB

CLOB

, or

NCLOB

columns, the JDBC driver transfers

the data to the client. This data can be accessed as a stream. To manipulate

BLOB

CLOB

, or

NCLOB

data from JDBC, use methods in the Oracle extension classes

oracle.sql.BLOB

oracle.sql.CLOB

and

oracle.sql.NCLOB

. These classes provide specific functionality, such

as reading from the

BLOB

CLOB

, or

NCLOB

into an input stream, writing from an output stream

Chapter 12

About Streaming CHAR, VARCHAR, or RAW Columns

12-7

into a

BLOB

CLOB

, or

NCLOB

, determining the length of a

BLOB

CLOB

, or

NCLOB

, and

closing a

BLOB

CLOB

, or

NCLOB

Note:

Starting from Oracle Database 12c Release 1 (12.1), the concrete classes in

the

oracle.sql

package are deprecated and replaced with the interfaces in

the

oracle.jdbc

package. Oracle recommends you to use the methods

available in the

java.sql

package, where possible, for standard compatibility

and methods available in the

oracle.jdbc

package for Oracle specific

extensions. Refer to MoS Note 1364193.1 for more information about these

interfaces.

See Also:

"Data Interface for LOBs"

Streaming BFILEs

An external file, or BFILE, is used to store a locator to a file outside the database. The

file can be stored somewhere on the file system of the data server. The locator points

to the actual location of the file.

When a query fetches one or more

BFILE

columns, the JDBC driver transfers the file to

the client as required. The data can be accessed as a stream To manipulate BFILE

data from JDBC, use methods in the Oracle extension class

oracle.sql.BFILE

. This

class provides specific functionality, such as reading from the BFILE into an input

stream, writing from an output stream into a BFILE, determining the length of a BFILE,

and closing a BFILE.

12.5 Relation Between Data Streaming and Multiple

Columns

If a query fetches multiple columns and one of the columns contains a data stream,

then the contents of the columns following the stream column are not available until

the stream has been read, and the stream column is no longer available once any

following column is read. Any attempt to read a column beyond a streaming column

closes the streaming column.

Streaming Example with Multiple Columns

Consider the following code:

ResultSet rset = stmt.executeQuery

("select DATECOL, LONGCOL, NUMBERCOL from TABLE");

while rset.next()

{

//get the date data

java.sql.Date date = rset.getDate(1);

Chapter 12

Relation Between Data Streaming and Multiple Columns

12-8

// get the streaming data

InputStream is = rset.getAsciiStream(2);

// Open a file to store the gif data

FileOutputStream file = new FileOutputStream ("ascii.dat");

// Loop, reading from the ascii stream and

// write to the file

int chunk;

while ((chunk = is.read ()) != -1)

file.write(chunk);

// Close the file

file.close();

//get the number column data

int n = rset.getInt(3);

}

The incoming data for each row has the following shape:

As you process each row of the result set, you must complete any processing of the stream

column before reading the number column.

Bypassing Streaming Data Columns

There may be situations where you want to avoid reading a column that contains streaming

data. If you do not want to read such data, then call the

method of the stream object.

This method discards the stream data and enables the driver to continue reading data from

all the columns that contain non-streaming data and follow the column containing streaming

data. Even though you are intentionally discarding the stream, it is a good programming

practice to retrieve the columns in the same order as in the

SELECT

statement.

In the following example, the stream data in the

LONG

column is discarded and the data from

only the

DATE

and

NUMBER

column is recovered:

ResultSet rset = stmt.executeQuery

("select DATECOL, LONGCOL, NUMBERCOL from TABLE");

while rset.next()

{

//get the date

java.sql.Date date = rset.getDate(1);

// access the stream data and discard it with close()

InputStream is = rset.getAsciiStream(2);

is.close();

// get the number column data

int n = rset.getInt(3);

}

Related Topics

• About Streaming Data Precautions

• About Streaming LOBs and External Files

Chapter 12

Relation Between Data Streaming and Multiple Columns

12-9

12.6 Closing a Stream

You can discard the data from a stream at any time by calling the

method. It is a

good programming practice to close the stream when you no longer need it. For

example:

...

InputStream is = rset.getAsciiStream(2);

is.close();

Note:

Closing a stream has little performance effect on a LONG or LONG RAW

column. All of the data still move across the network and the driver must read

the bits from the network.

Related Topics

• Relation Between Data Streaming and Multiple Columns

• About Streaming Data Precautions

12.7 Notes and Precautions on Streams

This section discusses several cautionary issues regarding the use of streams:

• About Streaming Data Precautions

• About Using Streams to Avoid Limits on setBytes and setString

• Relation Between Streaming and Row Prefetching

12.7.1 About Streaming Data Precautions

This section describes some of the precautions you must take to ensure that you do

not accidentally discard or lose your stream data. The drivers automatically discard

stream data if you perform any JDBC operation that communicates with the database,

other than reading the current stream. Two common precautions are:

• Use the stream data after you access it.

To recover the data from a column containing a data stream, it is not enough to

fetch the column. You must immediately process the contents of the column.

Otherwise, the contents will be discarded when you fetch the next column.

• Call the stream column in the same order as in the

SELECT

statement.

If your query fetches multiple columns, the database sends each row as a set of

bytes representing the columns in the

SELECT

order. If one of the columns contains

stream data, then the database sends the entire data stream before proceeding to

the next column.

If you do not use the order as in the

SELECT

statement to access data, then you

can lose the stream data. That is, if you bypass the stream data column and

Chapter 12

Closing a Stream

12-10

access data in a column that follows it, then the stream data will be lost. For example, if

you try to access the data for the

NUMBER

column before reading the data from the stream

data column, then the JDBC driver first reads then discards the streaming data

automatically. This can be very inefficient if the

LONG

column contains a large amount of

data.

If you try to access the

LONG

column later in the program, then the data will not be

available and the driver will return a "

Stream Closed

" error.

The later point is illustrated in the following example:

ResultSet rset = stmt.executeQuery

("select DATECOL, LONGCOL, NUMBERCOL from TABLE");

while rset.next()

{

int n = rset.getInt(3); // This discards the streaming data

InputStream is = rset.getAsciiStream(2);

// Raises an error: stream closed.

}

If you get the stream but do not use it before you get the

NUMBER

column, then the stream still

closes automatically:

ResultSet rset = stmt.executeQuery

("select DATECOL, LONGCOL, NUMBERCOL from TABLE");

while rset.next()

{

InputStream is = rset.getAsciiStream(2); // Get the stream

int n = rset.getInt(3);

// Discards streaming data and closes the stream

}

int c = is.read(); // c is -1: no more characters to read-stream closed

12.7.2 About Using Streams to Avoid Limits on setBytes and setString

Starting from Oracle Database 12c, the size limit of the data that is used with the

setBytes

and

setString

methods, have been increased significantly. Any Java

byte

array can be

passed to

setBytes

, and any Java

String

can be passed to

setString

. The JDBC driver

automatically switches to using

setBinaryStream

setCharacterStream

or to using

setBytesForBlob

setStringForClob

, depending on the size of the data, whether the

statement is SQL or PL/SQL, and the driver used.

There are some limitation with earlier versions of Oracle Database and in the server-side

internal driver.

Related Topics

• Data Interface for LOBs

The data interface for LOBs includes a set of Java and OCI APIs that are extended to

work with LOB data types.

12.7.3 Relation Between Streaming and Row Prefetching

If the JDBC driver encounters a column containing a data stream, then row fetch size is set

back to one. Row fetch size is an Oracle performance enhancement that enables multiple

rows of data to be retrieved with each trip to the database.

Chapter 12

Notes and Precautions on Streams

12-11

Working with Oracle Object Types

This chapter describes the Java Database Connectivity (JDBC) support for user-defined

object types. It discusses functionality of the generic, weakly typed

oracle.sql.STRUCT

class,

as well as how to map to custom Java classes that implement either the JDBC standard

SQLData

interface or the Oracle-specific

OracleData

interface.

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.STRUCT

class

is deprecated and replaced with the

oracle.jdbc.OracleStruct

interface, which is

a part of the

oracle.jdbc

package. Oracle strongly recommends you to use the

methods available in the

java.sql

package, where possible, for standard

compatibility and methods available in the

oracle.jdbc

package for Oracle specific

extensions. Refer to MoS Note 1364193.1 for more information about the

oracle.jdbc.OracleStruct

interface.

The following topics are covered:

• About Mapping Oracle Objects

• About Using the Default STRUCT Class for Oracle Objects

• About Creating and Using Custom Object Classes for Oracle Objects

• Object-Type Inheritance

• About Describing an Object Type

Related Topics

• About Using PL/SQL Types

13.1 About Mapping Oracle Objects

Oracle object types provide support for composite data structures in the database. For

example, you can define a

Person

type that has the attributes

name

CHAR

type,

phoneNumber

CHAR

type, and

employeeNumber

NUMBER

type.

Oracle provides tight integration between its Oracle object features and its JDBC functionality.

You can use a standard, generic JDBC type to map to Oracle objects, or you can customize

the mapping by creating custom Java type definition classes.

13-1

Note:

In this book, Java classes that you create to map to Oracle objects will be

referred to as custom Java classes or, more specifically, custom object

classes. This is as opposed to custom references classes, which are Java

classes that map to object references, and custom collection classes,

which are Java classes that map to Oracle collections.

Custom object classes can implement either a standard JDBC interface or an Oracle

extension interface to read and write data. JDBC materializes Oracle objects as

instances of particular Java classes. Two main steps in using JDBC to access Oracle

objects are:

1. Creating the Java classes for the Oracle objects

2. Populating these classes. You have the following options:

• Let JDBC materialize the object as a

STRUCT

object.

• Explicitly specify the mappings between Oracle objects and Java classes.

This includes customizing your Java classes for object data. The driver then

must be able to populate instances of the custom object classes that you

specify. This imposes a set of constraints on the Java classes. To satisfy these

constraints, you can define your classes to implement either the JDBC

standard

java.sql.SQLData

interface or the Oracle extension

oracle.jdbc.OracleData

interface.

Note:

When you use the

SQLData

interface, you must use a Java type map to

specify your SQL-Java mapping, unless weakly typed

java.sql.Struct

objects will suffice.

13.2 About Using the Default STRUCT Class for Oracle

Objects

This section covers the following topics:

• Overview of Using the Struct Class

• Retrieving STRUCT Objects and Attributes

• About Creating STRUCT Objects

• Binding STRUCT Objects into Statements

• STRUCT Automatic Attribute Buffering

Chapter 13

About Using the Default STRUCT Class for Oracle Objects

13-2

13.2.1 Overview of Using the Struct Class

If you choose not to supply a custom Java class for your SQL-Java mapping for an Oracle

object, then Oracle JDBC materializes the object as an object that implements the

java.sql.Struct

interface.

You would typically want to use

STRUCT

objects, instead of custom Java objects, in situations

where you do not know the actual SQL type. For example, your Java application might be a

tool to manipulate arbitrary object data within the database, as opposed to being an end-user

application. You can select data from the database into

STRUCT

objects and create

STRUCT

objects for inserting data into the database.

STRUCT

objects completely preserve data,

because they maintain the data in SQL format. Using

STRUCT

objects is more efficient and

more precise in situations where you do not need the information in an application specific

form.

13.2.2 Retrieving STRUCT Objects and Attributes

This section discusses how to retrieve and manipulate Oracle objects and their attributes,

using either Oracle-specific features or JDBC 2.0 standard features.

Note:

The JDBC driver seamlessly handles embedded objects, that is,

STRUCT

objects that

are attributes of

STRUCT

objects, in the same way that it typically handles objects.

When the JDBC driver retrieves an attribute that is an object, it follows the same

rules of conversion by using the type map, if it is available, or by using default

mapping.

Retrieving an Oracle Object as a java.sql.Struct Object

Alternatively, in the preceding example, you can use standard JDBC functionality, such as

getObject

, to retrieve an Oracle object from the database as an instance of

java.sql.Struct

. The

getObject

method returns a

java.lang.Object

, so, you must cast the

output of the method to

Struct

. For example:

ResultSet rs= stmt.executeQuery("SELECT * FROM struct_table");

java.sql.Struct jdbcStruct = (java.sql.Struct)rs.getObject(1);

Retrieving Attributes as oracle.sql Types

If you want to retrieve Oracle object attributes from a

STRUCT

Struct

instance as

oracle.sql

types, then use the

getOracleAttributes

method of the

oracle.sql.STRUCT

class, as follows:

oracle.sql.Datum[] attrs = oracleSTRUCT.getOracleAttributes();

or:

oracle.sql.Datum[] attrs = ((oracle.sql.STRUCT)jdbcStruct).getOracleAttributes();

Chapter 13

About Using the Default STRUCT Class for Oracle Objects

13-3

Retrieving Attributes as Standard Java Types

If you want to retrieve Oracle object attributes as standard Java types from a

STRUCT

Struct

instance, use the standard

getAttributes

method:

Object[] attrs = jdbcStruct.getAttributes();

Note:

Oracle JDBC drivers cache array and structure descriptors. This provides

enormous performance benefits. However, it means that if you change the

underlying type definition of a structure type in the database, the cached

descriptor for that structure type will become stale and your application will

receive a

SQLException

exception.

13.2.3 About Creating STRUCT Objects

For information about creating STRUCT objects, refer to "Package oracle.sql".

Note:

If you have already fetched from the database a

STRUCT

of the appropriate

SQL object type, then the easiest way to get a

STRUCT

descriptor is to call

getDescriptor

on one of the fetched

STRUCT

objects. Only one

STRUCT

descriptor is needed for any one SQL object type.

13.2.4 Binding STRUCT Objects into Statements

To bind an

oracle.sql.STRUCT

object to a prepared statement or callable statement,

you can either use the standard

setObject

method (specifying the type code), or cast

the statement object to an Oracle statement type and use the Oracle extension

setOracleObject

method. For example:

PreparedStatement ps= conn.prepareStatement("text_of_prepared_statement");

Struct mySTRUCT = conn.createStruct (...);

ps.setObject(1, mySTRUCT, Types.STRUCT);

or:

PreparedStatement ps= conn.prepareStatement("text_of_prepared_statement");

Struct mySTRUCT = conn.createStruct (...);

((OraclePreparedStatement)ps).setOracleObject(1, mySTRUCT);

13.2.5 STRUCT Automatic Attribute Buffering

Oracle JDBC driver furnishes public methods to enable and disable buffering of

STRUCT

attributes.

Chapter 13

About Using the Default STRUCT Class for Oracle Objects

13-4

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.STRUCT

class

is deprecated and replaced with the

oracle.jdbc.OracleStruct

interface, which is

a part of the

oracle.jdbc

package. Oracle strongly recommends you to use the

methods available in the

java.sql

package, where possible, for standard

compatibility and methods available in the

oracle.jdbc

package for Oracle specific

extensions. Refer to MoS Note 1364193.1 for more information about the

oracle.jdbc.OracleStruct

interface.

The following methods are included with the

oracle.sql.STRUCT

class:

•

public void setAutoBuffering(boolean enable)

•

public boolean getAutoBuffering()

The

setAutoBuffering(boolean)

method enables or disables auto-buffering. The

getAutoBuffering

method returns the current auto-buffering mode. By default, auto-buffering

is disabled.

It is advisable to enable auto-buffering in a JDBC application when the

STRUCT

attributes are

accessed more than once by the

getAttributes

and

getArray

methods, presuming the

ARRAY

data is able to fit into the Java Virtual Machine (JVM) memory without overflow.

Note:

Buffering the converted attributes may cause the JDBC application to consume a

significant amount of memory.

When you enable auto-buffering, the

oracle.sql.STRUCT

object keeps a local copy of all the

converted attributes. This data is retained so that subsequent access of this information does

not require going through the data format conversion process.

Related Topics

• ARRAY Automatic Element Buffering

13.3 About Creating and Using Custom Object Classes for

Oracle Objects

This section covers the following topics:

• Overview of Creating and Using Custom Object Classes

• Relative Advantages of OracleData versus SQLData

• About Type Maps for SQLData Implementations

• About Creating Type Map and Defining Mappings for a SQLData Implementation

• About Reading and Writing Data with a SQLData Implementation

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-5

• About the OracleData Interface

• About Reading and Writing Data with an OracleData Implementation

• Additional Uses of OracleData

13.3.1 Overview of Creating and Using Custom Object Classes

If you want to create custom object classes for your Oracle objects, then you must

define entries in the type map that specify the custom object classes that the drivers

instantiate for the corresponding Oracle objects.

You must also provide a way to create and populate instances of the custom object

class from the Oracle object and its attribute data. The driver must be able to read

from a custom object class and write to it. In addition, the custom object class can

provide

getXXX

and

setXXX

methods corresponding to the attributes of the Oracle

object, although this is not necessary. To create and populate the custom classes and

provide these read/write capabilities, you can choose between the following interfaces:

• The JDBC standard

SQLData

interface

• The

OracleData

and

OracleDataFactory

interfaces provided by Oracle

The custom object class you create must implement one of these interfaces. The

OracleData

interface can also be used to implement the custom reference class

corresponding to the custom object class. However, if you are using the

SQLData

interface, then you can use only weak reference types in Java, such as

java.sql.Ref

oracle.sql.REF

. The

SQLData

interface is for mapping SQL objects only.

As an example, assume you have an Oracle object type,

EMPLOYEE

, in the database

that consists of two attributes:

Name

, which is of the

CHAR

type and

EmpNum

, which is of

the

NUMBER

type. You use the type map to specify that the

EMPLOYEE

object should map

to a custom object class that you call

JEmployee

. You can implement either the

SQLData

OracleData

interface in the

JEmployee

class.

Related Topics

• Object-Type Inheritance

13.3.2 Relative Advantages of OracleData versus SQLData

In deciding which of the two interface implementations to use, you need to consider

the advantages of

OracleData

and

SQLData

The

SQLData

interface is for mapping SQL objects only. The

OracleData

interface is

more flexible, enabling you to map SQL objects as well as any other SQL type for

which you want to customize processing. You can create an

OracleData

implementation from any data type found in Oracle Database. This could be useful, for

example, for serializing

RAW

data in Java.

Advantages of the OracleData Interface

The advantages of the

OracleData

interface are:

• It does not require an entry in the type map for the Oracle object.

• It has awareness of Oracle extensions.

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-6

• You can construct an

OracleData

from an

oracle.sql.STRUCT

. This is more efficient

because it avoids unnecessary conversions to native Java types.

• You can obtain the corresponding JDBC object from

OracleData

, using the

toJDBCObject

method.

Advantages of SQLData

SQLData

is a JDBC standard that makes your code portable.

13.3.3 About Type Maps for SQLData Implementations

If you use the

SQLData

interface in a custom object class, then you must create type map

entries that specify the custom object class to use in mapping the Oracle object type to Java.

You can either use the default type map of the connection object or a type map that you

specify when you retrieve the data from the result set. The

getObject

method of the

ResultSet

interface has a signature that lets you specify a type map. You can use either of

the following:

rs.getObject(int columnIndex);

rs.getObject(int columnIndex, Map map);

When using a SQLData implementation, if you do not include a type map entry, then the

object maps to the

oracle.jdbc.OracleStruct

interface by default.

OracleData

implementations, by contrast, have their own mapping functionality so that a type map entry

is not required. When using an

OracleData

implementation, use the Oracle

getObject(int

columnindex, OracleDataFactory factory)

method.

The type map relates a Java class to the SQL type name of an Oracle object. This one-to-

one mapping is stored in a hash table as a keyword-value pair. When you read data from an

Oracle object, the JDBC driver considers the type map to determine which Java class to use

to materialize the data from the Oracle object type. When you write data to an Oracle object,

the JDBC driver gets the SQL type name from the Java class by calling the

getSQLTypeName

method of the

SQLData

interface. The actual conversion between SQL and Java is performed

by the driver.

The attributes of the Java class that corresponds to an Oracle object can use either Java

native types or Oracle native types to store attributes.

Related Topics

• About Creating and Using Custom Object Classes for Oracle Objects

13.3.4 About Creating Type Map and Defining Mappings for a SQLData

Implementation

This section covers the following topics:

• Overview of Creating a Type Map and Defining Mappings

• Adding Entries to an Existing Type Map

• Creating a New Type Map

• About Materializing Object Types not Specified in the Type Map

Chapter 13

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13-7

13.3.4.1 Overview of Creating a Type Map and Defining Mappings

When using a

SQLData

implementation, the JDBC applications programmer is

responsible for providing a type map, which must be an instance of a class that

implements the standard

java.util.Map

interface.

You have the option of creating your own class to accomplish this, but the standard

java.util.Hashtable

class meets the requirement.

Hashtable

and other classes used for type maps implement a

put

method that takes

keyword-value pairs as input, where each key is a fully qualified SQL type name and

the corresponding value is an instance of a specified Java class.

A type map is associated with a connection instance. The standard

java.sql.Connection

interface and the Oracle-specific

oracle.jdbc.OracleConnection

interface include a

getTypeMap

method. Both return a

Map

object.

13.3.4.2 Adding Entries to an Existing Type Map

When a connection instance is first established, the default type map is empty. You

must populate it.

Perform the following general steps to add entries to an existing type map:

1. Use the

getTypeMap

method of your

OracleConnection

object to return the type

map object of the connection. The

getTypeMap

method returns a

java.util.Map

object. For example, presuming an

OracleConnection

instance

oraconn

java.util.Map myMap = oraconn.getTypeMap();

Note:

If the type map in the

OracleConnection

instance has not been

initialized, then the first call to

getTypeMap

returns an empty map.

2. Use the

put

method of the type map to add map entries. The

put

method takes

two arguments: a SQL type name string and an instance of a specified Java class

that you want to map to.

myMap.put(sqlTypeName, classObject);

The

sqlTypeName

is a string that represents the fully qualified name of the SQL

type in the database. The

classObject

is the Java class object to which you want

to map the SQL type. Get the class object with the

Class.forName

method, as

follows:

myMap.put(sqlTypeName, Class.forName(className));

For example, if you have a

PERSON

SQL data type defined in the

CORPORATE

database schema, then map it to a

Person

Java class defined as

Person

with this

statement:

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-8

myMap.put("CORPORATE.PERSON", Class.forName("Person"));

oraconn.setTypeMap(newMap);

The map has an entry that maps the

PERSON

SQL data type in the

CORPORATE

database to

the

Person

Java class.

Note:

SQL type names in the type map must be all uppercase, because that is how

Oracle Database stores SQL names.

13.3.4.3 Creating a New Type Map

Perform the following general steps to create a new type map. This example uses an

instance of

java.util.Hashtable

, which extends

java.util.Dictionary

and implements

java.util.Map

1. Create a new type map object.

Hashtable newMap = new Hashtable();

2. Use the

put

method of the type map object to add entries to the map. For example, if you

have an

EMPLOYEE

SQL type defined in the

CORPORATE

database, then you can map it to

Employee

class object defined by

Employee.java

, as follows:

newMap.put("CORPORATE.EMPLOYEE", class.forName("Employee"));

3. When you finish adding entries to the map, you must use the

setTypeMap

method of the

OracleConnection

object to overwrite the existing type map of the connection. For

example:

oraconn.setTypeMap(newMap);

In this example, the

setTypeMap

method overwrites the original map of the

oraconn

connection object with

newMap

Note:

The default type map of a connection instance is used when mapping is

required but no map name is specified, such as for a result set

getObject

call

that does not specify the map as input.

13.3.4.4 About Materializing Object Types not Specified in the Type Map

If you do not provide a type map with an appropriate entry when using a

getObject

call, then

the JDBC driver will materialize an Oracle object as an instance of the

oracle.jdbc.OracleStruct

interface. If the Oracle object type contains embedded objects

and they are not present in the type map, then the driver will materialize the embedded

objects as instances of

oracle.jdbc.OracleStruct

as well. If the embedded objects are

present in the type map, then a call to the

getAttributes

method will return embedded

objects as instances of the specified Java classes from the type map.

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-9

13.3.5 About Reading and Writing Data with a SQLData

Implementation

This section describes how to read data from an Oracle object or write data to an

Oracle object if your corresponding Java class implements

SQLData

Reading SQLData Objects from a Result Set

The following text summarizes the steps to read data from an Oracle object into your

Java application when you choose the

SQLData

implementation for your custom object

class.

These steps assume you have already defined the Oracle object type, created the

corresponding custom object class, updated the type map to define the mapping

between the Oracle object and the Java class, and defined a statement object

stmt

1. Query the database to read the Oracle object into a JDBC result set.

ResultSet rs = stmt.executeQuery("SELECT emp_col FROM personnel");

The

PERSONNEL

table contains one column,

EMP_COL

, of SQL type

EMP_OBJECT

. This

SQL type is defined in the type map to map to the Java class

Employee

2. Use the

getObject

method of Oracle result set to populate an instance of your

custom object class with data from one row of the result set. The

getObject

method returns the user-defined

SQLData

object because the type map contains an

entry for

Employee

if (rs.next())

Employee emp = (Employee)rs.getObject(1);

Note that if the type map did not have an entry for the object, then the

getObject

method will return an

oracle.jdbc.OracleStruct

object. Cast the output to type

OracleStruct

because the

getObject

method signature returns the generic

java.lang.Object

type.

if (rs.next())

OracleStruct empstruct = (OracleStruct)rs.getObject(1);

The

getObject

method calls

readSQL

, which, in turn, calls

readXXX

from the

SQLData

interface.

Note:

If you want to avoid using the defined type map, then use the

getSTRUCT

method. This method always returns a

STRUCT

object, even if there is a

mapping entry in the type map.

3. If you have

get

methods in your custom object class, then use them to read data

from your object attributes. For example, if

EMPLOYEE

has the attributes

EmpName

type

CHAR

and

EmpNum

of type

NUMBER

, then provide a

getEmpName

method that

returns a Java

String

and a

getEmpNum

method that returns an

int

value. Then

call them in your Java application, as follows:

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-10

String empname = emp.getEmpName();

int empnumber = emp.getEmpNum();

Retrieving SQLData Objects from a Callable Statement OUT Parameter

Consider you have a

CallableStatement

instance,

, that calls a PL/SQL function

GETEMPLOYEE

. The program passes an employee number to the function. The function returns

the corresponding

Employee

object. To retrieve this object you do the following:

1. Prepare a

CallableStatement

to call the

GETEMPLOYEE

function, as follows:

CallableStatement ocs = conn.prepareCall("{ ? = call GETEMPLOYEE(?) }");

2. Declare the

empnumber

as the input parameter to

GETEMPLOYEE

. Register the

SQLData

object as the

OUT

parameter, with the type code

OracleTypes.STRUCT

. Then, run the

statement. This can be done as follows:

cs.setInt(2, empnumber);

cs.registerOutParameter(1, OracleTypes.STRUCT, "EMP_OBJECT");

cs.execute();

3. Use the

getObject

method to retrieve the employee object.

Employee emp = (Employee)cs.getObject(1);

If there is no type map entry, then the

getObject

method will return a

java.sql.Struct

object.

Struct emp = cs.getObject(1);

Passing SQLData Objects to a Callable Statement as an IN Parameter

Suppose you have a PL/SQL function

addEmployee(?)

that takes an

Employee

object as an

parameter and adds it to the

PERSONNEL

table. In this example,

emp

is a valid

Employee

object.

1. Prepare an

CallableStatement

to call the

addEmployee(?)

function.

CallableStatement cs =

conn.prepareCall("{ call addEmployee(?) }");

2. Use

setObject

to pass the

emp

object as an

parameter to the callable statement.

Then, call the statement.

cs.setObject(1, emp);

cs.execute();

Writing Data to an Oracle Object Using a SQLData Implementation

The following text describes the steps in writing data to an Oracle object from your Java

application when you choose the

SQLData

implementation for your custom object class.

This description assumes you have already defined the Oracle object type, created the

corresponding Java class, and updated the type map to define the mapping between the

Oracle object and the Java class.

1. If you have

set

methods in your custom object class, then use them to write data from

Java variables in your application to attributes of your Java data type object.

emp.setEmpName(empname);

emp.setEmpNum(empnumber);

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-11

2. Prepare a statement that updates an Oracle object in a row of a database table, as

appropriate, using the data provided in your Java data type object.

PreparedStatement pstmt = conn.prepareStatement

("INSERT INTO PERSONNEL VALUES (?)");

3. Use the

setObject

method of the prepared statement to bind your Java data type

object to the prepared statement.

pstmt.setObject(1, emp);

4. Run the statement, which updates the database.

pstmt.executeUpdate();

13.3.6 About the OracleData Interface

You can create a custom object class that implements the

oracle.jdbc.OracleData

and the

oracle.jdbc.OracleDataFactory

interfaces to make an Oracle object and its

attribute data available to Java applications. The

OracleData

and

OracleDataFactory

interfaces are Oracle-specific and are not a part of the JDBC standard.

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

OracleData

and the

OracleDataFactory

interfaces replace the

ORAData

and the

ORADataFactory

interfaces.

Understanding the OracleData Interface Features

The

OracleData

interface has the following advantages:

• It supports Oracle extensions to the standard JDBC types.

• It does not require a type map to specify the names of the Java custom classes

you want to create.

• It provides better performance.

OracleData

works directly with

Datum

types, the

internal format the driver uses to hold Oracle objects.

The

OracleData

and the

OracleDataFactory

interfaces perform the following:

• The

toJDBCObject

method of the

OracleData

class transforms the data into an

oracle.jdbc.*

representation.

•

OracleDataFactory

specifies a

create

method equivalent to a constructor for the

custom object class. It creates and returns an

OracleData

instance. The JDBC

driver uses the

create

method to return an instance of the custom object class to

your Java application. It takes as input a

java.lang.Object

object and an integer

indicating the corresponding SQL type code as specified in the

OracleTypes

class.

OracleData

and

OracleDataFactory

have the following definitions:

package oracle.jdbc;

import java.sql.Connection;

import java.sql.SQLException;

public interface OracleData

{

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-12

public Object toJDBCObject(Connection conn) throws SQLException;

}

package oracle.jdbc;

import java.sql.SQLException;

public interface OracleDataFactory

{

public OracleData create(Object jdbcValue, int sqlType) throws SQLException;

}

Where

conn

represents the Connection object,

jdbcValue

represents an object of type

java.lang.object

that is to be used to initialize the Object being created, and

sqlType

represents the SQL type of the specified

Datum

object.

Retrieving and Inserting Object Data

The JDBC drivers provide the following methods to retrieve and insert object data as

instances of

OracleData

You can retrieve the object data in one of the following ways:

• Use the following

getObject

method of the Oracle-specific

OracleResultSet

interface:

ors.getObject(int col_index, OracleDataFactory factory

);

This method takes as input the column index of the data in your result set and an

OracleDataFactory

instance. For example, you can implement a

getOracleDataFactory

method in your custom object class to produce the

OracleDataFactory

instance to input

to the

getObject

method. The type map is not required when using Java classes that

implement

OracleData

• Use the standard

getObject(index, map)

method specified by the

ResultSet

interface

to retrieve data as instances of

OracleData

. In this case, you must have an entry in the

type map that identifies the factory class to be used for the given object type and its

corresponding SQL type name.

You can insert object data in one of the following ways:

• Use the following

setObject

method of the Oracle-specific

OraclePreparedStatement

class:

setObject(int bind_index, Object custom_object);

This method takes as input the parameter index of the bind variable and an instance of

OracleData

as the name of the object containing the variable.

• Use the standard

setObject

method specified by the

PreparedStatement

interface. You

can also use this method, in its different forms, to insert

OracleData

instances without

requiring a type map.

The following sections describe the

getObject

and

setObject

methods.

To continue the example of an Oracle object

EMPLOYEE

, you might have something like the

following in your Java application:

OracleData obj = ors.getObject(1, Employee.getOracleDataFactory());

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-13

In this example,

ors

is an instance of the

OracleResultSet

interface,

getObject

is a

method in the

OracleResultSet

interface used to retrieve an

OracleData

object, and

the

EMPLOYEE

is in column 1 of the result set. The

static

Employee.getOracleDataFactory

method will return an

OracleDataFactory

to the

JDBC driver. The JDBC driver will call

create(

) from this object, returning to your Java

application an instance of the

Employee

class populated with data from the result set.

Note:

•

OracleData

and

OracleDataFactory

are defined as separate interfaces

so that different Java classes can implement them if you wish.

• To use the

OracleData

interface, your custom object classes must import

oracle.jdbc.*

13.3.7 About Reading and Writing Data with an OracleData

Implementation

This section describes how to read data from an Oracle object or write data to an

Oracle object if your corresponding Java class implements

OracleData

Reading Data from an Oracle Object Using an OracleData Implementation

The following text summarizes the steps in reading data from an Oracle object into

your Java application. These steps apply whether you implement

OracleData

manually or use Oracle JVM Web Service Call-Out utility to produce your custom

object classes.

These steps assume you have already defined the Oracle object type, created the

corresponding custom object class or had Oracle JVM Web Service Call-Out utility

create it for you, and defined a statement object

stmt

1. Query the database to read the Oracle object into a result set, casting it to an

Oracle result set.

OracleResultSet ors = (OracleResultSet)stmt.executeQuery

("SELECT Emp_col FROM PERSONNEL");

Where

PERSONNEL

is a one-column table. The column name is

Emp_col

of type

Employee_object

2. Use the

getObject

method of Oracle result set to populate an instance of your

custom object class with data from one row of the result set. The

getObject

method returns a

java.lang.Object

object, which you can cast to your specific

custom object class.

if (ors.next())

Employee emp = (Employee)ors.getObject(1,

Employee.getOracleDataFactory());

or:

if (ors.next())

Object obj = ors.getObject(1, Employee.getOracleDataFactory());

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-14

This example assumes that

Employee

is the name of your custom object class and

ors

the name of your

OracleResultSet

instance.

For example, if the SQL type name for your object is

EMPLOYEE

, then the corresponding

Java class is

Employee

, which will implement

OracleData

. The corresponding Factory

class is

EmployeeFactory

, which will implement

OracleDataFactory

Use this statement to declare the

EmployeeFactory

entry for your type map:

map.put ("EMPLOYEE", Class.forName ("EmployeeFactory"));

Then use the form of

getObject

where you specify the map object:

Employee emp = (Employee) rs.getObject (1, map);

If the default type map of the connection already has an entry that identifies the factory

class to be used for the given object type and its corresponding SQL type name, then you

can use this form of

getObject

Employee emp = (Employee) rs.getObject (1);

3. If you have

get

methods in your custom object class, then use them to read data from

your object attributes into Java variables in your application. For example, if

EMPLOYEE

has

EmpName

of type

CHAR

and

EmpNum

of type

NUMBER

, provide a

getEmpName

method that

returns a Java

String

and a

getEmpNum

method that returns an integer. Then call them in

your Java application as follows:

String empname = emp.getEmpName();

int empnumber = emp.getEmpNum();

Writing Data to an Oracle Object Using an OracleData Implementation

The following text summarizes the steps in writing data to an Oracle object from your Java

application. These steps apply whether you implement

OracleData

manually or use Oracle

JVM Web Service Call-Out utility to produce your custom object classes.

These steps assume you have already defined the Oracle object type and created the

corresponding custom object class.

Note:

The type map is not used when you are performing database

INSERT

and

UPDATE

operations.

1. If you have

set

methods in your custom object class, then use them to write data from

Java variables in your application to attributes of your Java data type object.

emp.setEmpName(empname);

emp.setEmpNum(empnumber);

2. Write an Oracle prepared statement that updates an Oracle object in a row of a database

table, as appropriate, using the data provided in your Java data type object.

OraclePreparedStatement opstmt = conn.prepareStatement

("UPDATE PERSONNEL SET Employee = ? WHERE Employee.EmpNum = 28959);

This assumes

conn

is your

Connection

object.

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-15

3. Use the

setObject

method of the

OraclePreparedStatement

interface to bind your

Java data type object to the prepared statement.

opstmt.setObject(1,emp);

The

setObject

method calls the

toJDBCObject

method of the custom object class

instance to retrieve an

oracle.jdbc.OracleStruct

object that can be written to

the database.

Note:

You can use your Java data type objects as either

OUT

bind

variables.

13.3.8 Additional Uses of OracleData

The

OracleData

interface offers far more flexibility than the

SQLData

interface. The

SQLData

interface is designed to let you customize the mapping of only Oracle object

types to Java types of your choice. Implementing the

SQLData

interface lets the JDBC

driver populate fields of a custom Java class instance from the original SQL object

data, and the reverse, after performing the appropriate conversions between Java and

SQL types.

The

OracleData

interface goes beyond supporting the customization of Oracle object

types to Java types. It lets you provide a mapping between Java object types and any

SQL type supported by the

oracle.sql

package.

You may find it useful to provide custom Java classes to wrap

oracle.sql.*

types and

then implement customized conversions or functionality as well. The following are

some possible scenarios:

• Performing encryption and decryption or validation of data

• Performing logging of values that have been read or are being written

• Parsing character columns, such as character fields containing URL information,

into smaller components

• Mapping character strings into numeric constants

• Making data into more desirable Java formats, such as mapping a

DATE

field to

java.util.Date

format

• Customizing data representation, for example, data in a table column is in feet but

you want it represented in meters after it is selected

• Serializing and deserializing Java objects

For example, use

OracleData

to store instances of Java objects that do not

correspond to a particular SQL object type in the database in columns of SQL type

RAW

. The

create

method in

OracleDataFactory

would have to implement a conversion

from an object of type

oracle.sql.RAW

to the desired Java object. The

toJDBCObject

method in

OracleData

would have to implement a conversion from the Java object to

oracle.sql.RAW

object. You can also achieve this using Java serialization.

Chapter 13

About Creating and Using Custom Object Classes for Oracle Objects

13-16

Upon retrieval, the JDBC driver transparently retrieves the raw bytes of data in the form of an

oracle.sql.RAW

and calls the

create

method of

OracleDataFactory

to convert the

oracle.sql.RAW

object to the desired Java class.

When you insert the Java object into the database, you can simply bind it to a column of type

RAW

to store it. The driver transparently calls the

OracleData

toJDBCObject

method to convert

the Java object to an

oracle.sql.RAW

object. This object is then stored in a column of type

RAW

in the database.

Support for the

OracleData

interfaces is also highly efficient because the conversions are

designed to work using

oracle.sql.*

formats, which happen to be the internal formats used

by the JDBC drivers. Moreover, the type map, which is necessary for the

SQLData

interface, is

not required when using Java classes that implement

OracleData

Related Topics

• About the OracleData Interface

13.4 Object-Type Inheritance

Object-type inheritance allows a new object type to be created by extending another object

type. The new object type is then a subtype of the object type from which it extends. The

subtype automatically inherits all the attributes and methods defined in the supertype. The

subtype can add attributes and methods and overload or override methods inherited from the

supertype.

Object-type inheritance introduces substitutability. Substitutability is the ability of a slot

declared to hold a value of type

in addition to any subtype of type

. Oracle JDBC drivers

handle substitutability transparently.

A database object is returned with its most specific type without losing information. For

example, if the

STUDENT_T

object is stored in a

PERSON_T

slot, Oracle JDBC driver returns a

Java object that represents the

STUDENT_T

object.

This section covers the following topics:

• About Creating Subtypes

• About Implementing Customized Classes for Subtypes

• About Retrieving Subtype Objects

• Creating Subtype Objects

• Sending Subtype Objects

• Accessing Subtype Data Fields

• Inheritance Metadata Methods

13.4.1 About Creating Subtypes

Create custom object classes if you want to have Java classes that explicitly correspond to

the Oracle object types. If you have a hierarchy of object types, you may want a

corresponding hierarchy of Java classes.

The most common way to create a database subtype in JDBC is to run a SQL

CREATE TYPE

command using the

execute

method of the

java.sql.Statement

interface. For example, you

want to create a type inheritance hierarchy as depicted in the following figure:

Chapter 13

Object-Type Inheritance

13-17

Figure 13-1 Type Inheritance Hierarchy

PERSON_T

PA RTTIMESTUDENT_T

STUDENT_T

The JDBC code for this can be as follows:

Statement s = conn.createStatement();

s.execute ("CREATE TYPE Person_T (SSN NUMBER, name VARCHAR2(30),

address VARCHAR2(255))");

s.execute ("CREATE TYPE Student_T UNDER Person_t (deptid NUMBER,

major VARCHAR2(100))");

s.execute ("CREATE TYPE PartTimeStudent_t UNDER Student_t (numHours NUMBER)");

In the following code, the

foo

member procedure in type

is overloaded and the

member procedure

overwrites the copy it inherits from type

CREATE TYPE T AS OBJECT (...,

MEMBER PROCEDURE foo(x NUMBER),

MEMBER PROCEDURE Print(),

...

NOT FINAL;

CREATE TYPE ST UNDER T (...,

MEMBER PROCEDURE foo(x DATE), <-- overload "foo"

OVERRIDING MEMBER PROCEDURE Print(), <-- override "print"

STATIC FUNCTION bar(...) ...

...

);

Once the subtypes have been created, they can be used as both columns of a base

table as well as attributes of an object type.

See Also:

Oracle Database Object-Relational Developer's Guide

13.4.2 About Implementing Customized Classes for Subtypes

In most cases, a customized Java class represents a database object type. When you

create a customized Java class for a subtype, the Java class can either mirror the

database object type hierarchy or not.

Chapter 13

Object-Type Inheritance

13-18

You can use either the

OracleData

SQLData

solution in creating classes to map to the

hierarchy of object types.

This section covers the following topics:

• About Using OracleData for Type Inheritance Hierarchy

• About UsingSQLData for Type Inheritance Hierarchy

13.4.2.1 About Using OracleData for Type Inheritance Hierarchy

Oracle recommends customized mappings, where Java classes implement the

oracle.sql.OracleData

interface.

OracleData

mapping requires the JDBC application to

implement the

OracleData

and

OracleDataFactory

interfaces. The class implementing the

OracleDataFactory

interface contains a factory method that produces objects. Each object

represents a database object.

The hierarchy of the class implementing the

OracleData

interface can mirror the database

object type hierarchy. For example, the Java classes mapping to

PERSON_T

and

STUDENT_T

are as follows:

Person.java using OracleData

Code for the

Person.java

class which implements the

OracleData

and

OracleDataFactory

interfaces:

public static OracleDataFactory getOracleDataFactory()

{

return _personFactory;

}

public Person () {}

public Person(NUMBER ssn, CHAR name, CHAR address)

{

this.ssn = ssn;

this.name = name;

this.address = address;

}

public Object toJDBCObject(OracleConnection c) throws SQLException

{

Object [] attributes = { ssn, name, address };

Struct struct = c.createStruct("HR.PERSON_T", attributes);

return struct;

}

public OracleData create(Object jdbcValue, int sqlType) throws SQLException

{

if (d == null) return null;

Object [] attributes = ((STRUCT) d).getOracleAttributes();

return new Person((NUMBER) attributes[0],

(CHAR) attributes[1],

(CHAR) attributes[2]);

}

Student.java extending Person.java

Code for the

Student.java

class, which extends the

Person.java

class:

Chapter 13

Object-Type Inheritance

13-19

class Student extends Person

{

static final Student _studentFactory = new Student ();

public NUMBER deptid;

public CHAR major;

public static OracleDataFactory getOracleDataFactory()

{

return _studentFactory;

}

public Student () {}

public Student (NUMBER ssn, CHAR name, CHAR address,

NUMBER deptid, CHAR major)

{

super (ssn, name, address);

this.deptid = deptid;

this.major = major;

}

public Object toJDBCObject(OracleConnection c) throws SQLException

{

Object [] attributes = { ssn, name, address, deptid, major };

Struct struct = c.createStruct("HR.STUDENT_T", attributes);

return struct;

}

public OracleData create(Object jdbcValue, int sqlType) throws SQLException

{

if (d == null) return null;

Object [] attributes = ((STRUCT) d).getOracleAttributes();

return new Student((NUMBER) attributes[0],

(CHAR) attributes[1],

(CHAR) attributes[2],

(NUMBER) attributes[3],

(CHAR) attributes[4]);

}

Customized classes that implement the

OracleData

interface do not have to mirror the

database object type hierarchy. For example, you could have declared the

Student

class without a superclass. In this case,

Student

would contain fields to hold the

inherited attributes from

PERSON_T

as well as the attributes declared by

STUDENT_T

OracleDataFactory Implementation

The JDBC application uses the factory class in querying the database to return

instances of

Person

or its subclasses, as in the following example:

ResultSet rset = stmt.executeQuery ("select person from tab1");

while (rset.next())

{

rset.getOracleData(1,Person.getOracleDataFactory());

...

}

Chapter 13

Object-Type Inheritance

13-20

A class implementing the

OracleDataFactory

interface should be able to produce instances

of the associated custom object type, as well as instances of any subtype, or at least all the

types you expect to support.

In the following example, the

PersonFactory.getOracleDataFactory

method returns a

factory that can handle

PERSON_T

STUDENT_T

, and

PARTTIMESTUDENT_T

objects, by returning

person

student

, or

parttimestudent

Java instances.

class PersonFactory implements OracleDataFactory

{

static final PersonFactory _factory = new PersonFactory ();

public static OracleDataFactory getOracleDataFactory()

{

return _factory;

}

public OracleData create(Object jdbcValue, int sqlType) throws SQLException

{

STRUCT s = (STRUCT) jdbcValue;

if (s.getSQLTypeName ().equals ("HR.PERSON_T"))

return Person.getOracleDataFactory ().create (jdbcValue, sqlType);

else if (s.getSQLTypeName ().equals ("HR.STUDENT_T"))

return Student.getOracleDataFactory ().create(jdbcValue, sqlType);

else if (s.getSQLTypeName ().equals ("HR.PARTTIMESTUDENT_T"))

return ParttimeStudent.getOracleDataFactory ().create(jdbcValue, sqlType);

else

return null;

}

The following example assumes a table

tabl1

, such as the following:

CREATE TABLE tabl1 (idx NUMBER, person PERSON_T);

INSERT INTO tabl1 VALUES (1, PERSON_T (1000, 'HR', '100 Oracle Parkway'));

INSERT INTO tabl1 VALUES (2, STUDENT_T (1001, 'Peter', '200 Oracle Parkway', 101,

'CS'));

INSERT INTO tabl1 VALUES (3, PARTTIMESTUDENT_T (1002, 'David', '300 Oracle Parkway',

102, 'EE'));

13.4.2.2 About UsingSQLData for Type Inheritance Hierarchy

The customized classes that implement the

java.sql.SQLData

interface can mirror the

database object type hierarchy. The

readSQL

and

writeSQL

methods of a subclass typically

call the corresponding superclass methods to read or write the superclass attributes before

reading or writing the subclass attributes. For example, the Java classes mapping to

PERSON_T

and

STUDENT_T

are as follows:

Person.java using SQLData

Code for the

Person.java

class, which implements the

SQLData

interface:

import java.sql.*;

public class Person implements SQLData

{

private String sql_type;

public int ssn;

public String name;

public String address;

Chapter 13

Object-Type Inheritance

13-21

public Person () {}

public String getSQLTypeName() throws SQLException { return sql_type; }

public void readSQL(SQLInput stream, String typeName) throws SQLException

{

sql_type = typeName;

ssn = stream.readInt();

name = stream.readString();

address = stream.readString();

}

public void writeSQL(SQLOutput stream) throws SQLException

{

stream.writeInt (ssn);

stream.writeString (name);

stream.writeString (address);

}

Student.java extending Student.java

Code for the

Student.java

class, which extends the

Person.java

class:

import java.sql.*;

public class Student extends Person

{

private String sql_type;

public int deptid;

public String major;

public Student () { super(); }

public String getSQLTypeName() throws SQLException { return sql_type; }

public void readSQL(SQLInput stream, String typeName) throws SQLException

{

super.readSQL (stream, typeName); // read supertype attributes

sql_type = typeName;

deptid = stream.readInt();

major = stream.readString();

}

public void writeSQL(SQLOutput stream) throws SQLException

{

super.writeSQL (stream); // write supertype

// attributes

stream.writeInt (deptid);

stream.writeString (major);

}

Although not required, it is recommended that the customized classes, which

implement the

SQLData

interface, mirror the database object type hierarchy. For

example, you could have declared the

Student

class without a superclass. In this

case,

Student

would contain fields to hold the inherited attributes from

PERSON_T

well as the attributes declared by

STUDENT_T

Chapter 13

Object-Type Inheritance

13-22

Student.java using SQLData

Code for the

Student.java

class, which does not extend the

Person.java

class, but

implements the SQLData interface directly:

import java.sql.*;

public class Student implements SQLData

{

private String sql_type;

public int ssn;

public String name;

public String address;

public int deptid;

public String major;

public Student () {}

public String getSQLTypeName() throws SQLException { return sql_type; }

public void readSQL(SQLInput stream, String typeName) throws SQLException

{

sql_type = typeName;

ssn = stream.readInt();

name = stream.readString();

address = stream.readString();

deptid = stream.readInt();

major = stream.readString();

}

public void writeSQL(SQLOutput stream) throws SQLException

{

stream.writeInt (ssn);

stream.writeString (name);

stream.writeString (address);

stream.writeInt (deptid);

stream.writeString (major);

}

13.4.3 About Retrieving Subtype Objects

In a typical JDBC application, a subtype object is returned as one of the following:

• A query result

• A PL/SQL

OUT

parameter

• A type attribute

You can use either the default mapping or the

SQLData

mapping or the

OracleData

mapping

to retrieve a subtype.

Using Default Mapping

By default, a database object is returned as an instance of the

oracle.jdbc.OracleStruct

interface. This instance may represent an object of either the declared type or subtype of the

declared type. If the

OracleStruct

interface represents a subtype object in the database,

then it contains the attributes of its supertype as well as those defined in the subtype.

Chapter 13

Object-Type Inheritance

13-23

Oracle JDBC driver returns database objects in their most specific type. The JDBC

application can use the

getSQLTypeName

method of the

OracleStruct

interface to

determine the SQL type of the

STRUCT

object. The following code shows this:

// tab1.person column can store PERSON_T, STUDENT_T and PARTIMESTUDENT_T objects

ResultSet rset = stmt.executeQuery ("select person from tab1");

while (rset.next())

{

oracle.sql.STRUCT s = (oracle.sql.STRUCT) rset.getObject(1);

if (s != null)

System.out.println (s.getSQLTypeName()); // print out the type name which

// may be HR.PERSON_T, HR.STUDENT_T or HR.PARTTIMESTUDENT_T

}

Using SQLData Mapping

With

SQLData

mapping, the JDBC driver returns the database object as an instance of

the class implementing the

SQLData

interface.

To use

SQLData

mapping in retrieving database objects, do the following:

1. Implement the container classes that implement the

SQLData

interface for the

desired object types.

2. Populate the connection type map with entries that specify what custom Java type

corresponds to each Oracle object type.

3. Use the

getObject

method to access the SQL object values.

The JDBC driver checks the type map for an entry match. If one exists, then the

driver returns the database object as an instance of the class implementing the

SQLData

interface.

The following code shows the whole SQLData customized mapping process:

// The JDBC application developer implements Person.java for PERSON_T,

// Student.java for STUDENT_T

// and ParttimeStudent.java for PARTTIMESTUDEN_T.

Connection conn = ...; // make a JDBC connection

// obtains the connection typemap

java.util.Map map = conn.getTypeMap ();

// populate the type map

map.put ("HR.PERSON_T", Class.forName ("Person"));

map.put ("HR.STUDENT_T", Class.forName ("Student"));

map.put ("HR.PARTTIMESTUDENT_T", Class.forName ("ParttimeStudent"));

// tab1.person column can store PERSON_T, STUDENT_T and PARTTIMESTUDENT_T

objects

ResultSet rset = stmt.executeQuery ("select person from tab1");

while (rset.next())

{

// "s" is instance of Person, Student or ParttimeStudent

Object s = rset.getObject(1);

if (s != null)

{

if (s instanceof Person)

System.out.println ("This is a Person");

else if (s instanceof Student)

Chapter 13

Object-Type Inheritance

13-24

System.out.println ("This is a Student");

else if (s instanceof ParttimeStudent)

System.out.pritnln ("This is a PartimeStudent");

else

System.out.println ("Unknown type");

}

The JDBC drivers check the connection type map for each call to the following:

•

getObject

method of the

java.sql.ResultSet

and

java.sql.CallableStatement

interfaces

•

getAttribute

method of the

java.sql.Struct

interface

•

getArray

method of the

java.sql.Array

interface

•

getValue

method of the

oracle.sql.REF

interface

Using OracleData Mapping

With

OracleData

mapping, the JDBC driver returns the database object as an instance of the

class implementing the

OracleData

interface.

Oracle JDBC driver needs to be informed of what Java class is mapped to the Oracle object

type. The following are the two ways to inform Oracle JDBC drivers:

• The JDBC application uses the

getObject(int idx, OracleDataFactory f)

method to

access database objects. The second parameter of the

getObject

method specifies an

instance of the factory class that produces the customized class. The

getObject

method

is available in the

OracleResultSet

and

OracleCallableStatement

interfaces.

• The JDBC application populates the connection type map with entries that specify what

custom Java type corresponds to each Oracle object type. The

getObject

method is

used to access the Oracle object values.

The second approach involves the use of the standard

getObject

method. The following

code example demonstrates the first approach:

// tab1.person column can store both PERSON_T and STUDENT_T objects

ResultSet rset = stmt.executeQuery ("select person from tab1");

while (rset.next())

{

Object s = rset.getObject(1, PersonFactory.getOracleDataFactory());

if (s != null)

{

if (s instanceof Person)

System.out.println ("This is a Person");

else if (s instanceof Student)

System.out.println ("This is a Student");

else if (s instanceof ParttimeStudent)

System.out.pritnln ("This is a PartimeStudent");

else

System.out.println ("Unknown type");

}

Chapter 13

Object-Type Inheritance

13-25

13.4.4 Creating Subtype Objects

There are cases where JDBC applications create database subtype objects with JDBC

drivers. These objects are sent either to the database as bind variables or are used to

exchange information within the JDBC application.

With customized mapping, the JDBC application creates either

SQLData

-based or

OracleData

-based objects, depending on the approach you choose, to represent

database subtype objects. With default mapping, the JDBC application creates

STRUCT

objects to represent database subtype objects. All the data fields inherited from the

supertype as well as all the fields defined in the subtype must have values. The

following code demonstrates this:

Connection conn = ... // make a JDBC connection

...

Object[] attrs = {

new Integer(1234), "HR", "500 Oracle Parkway", // data fields defined in

// PERSON_T

new Integer(102), "CS", // data fields defined in

// STUDENT_T

new Integer(4) // data fields defined in

// PARTTIMESTUDENT_T

};

Struct s = conn.createStruct("HR.PARTTIMESTUDENT", attrs);

is initialized with data fields inherited from

PERSON_T

and

STUDENT_T

, and data fields

defined in

PARTTIMESTUDENT_T

13.4.5 Sending Subtype Objects

In a typical JDBC application, a Java object that represents a database object is sent

to the databases as one of the following:

• A data manipulation language (DML) bind variable

• A PL/SQL

parameter

• An object type attribute value

The Java object can be an instance of the

STRUCT

class or an instance of the class

implementing either the

SQLData

OracleData

interface. Oracle JDBC driver will

convert the Java object into the linearized format acceptable to the database SQL

engine. Binding a subtype object is the same as binding a standard object.

13.4.6 Accessing Subtype Data Fields

While the logic to access subtype data fields is part of the customized class, this logic

for default mapping is defined in the JDBC application itself. The database objects are

returned as instances of the

oracle.jdbc.OracleStruct

class. The JDBC application

needs to call one of the following access methods in the

STRUCT

class to access the

data fields:

•

Object[] getAttribute()

•

oracle.sql.Datum[] getOracleAttribute()

Chapter 13

Object-Type Inheritance

13-26

Subtype Data Fields from the getAttribute Method

The

getAttribute

method of the

java.sql.Struct

interface is used in JDBC 2.0 to access

object data fields. This method returns a

java.lang.Object

array, where each array element

represents an object attribute. You can determine the individual element type by referencing

the corresponding attribute type in the JDBC conversion matrix. For example, a SQL

NUMBER

attribute is converted to a

java.math.BigDecimal

object. The

getAttribute

method returns

all the data fields defined in the supertype of the object type as well as data fields defined in

the subtype. The supertype data fields are listed first followed by the subtype data fields.

Subtype Data Fields from the getOracleAttribute Method

The

getOracleAttribute

method is an Oracle extension method and is more efficient than

the

getAttribute

method. The

getOracleAttribute

method returns an

oracle.sql.Datum

array to hold the data fields. Each element in the

oracle.sql.Datum

array represents an

attribute. You can determine the individual element type by referencing the corresponding

attribute type in the Oracle conversion matrix. For example, a SQL

NUMBER

attribute is

converted to an

oracle.sql.NUMBER

object. The

getOracleAttribute

method returns all the

attributes defined in the supertype of the object type, as well as attributes defined in the

subtype. The supertype data fields are listed first followed by the subtype data fields.

The following code shows the use of the

getAttribute

method:

// tab1.person column can store PERSON_T, STUDENT_T and PARTIMESTUDENT_T objects

ResultSet rset = stmt.executeQuery ("select person from tab1");

while (rset.next())

{

oracle.sql.STRUCT s = (oracle.sql.STRUCT) rset.getObject(1);

if (s != null)

{

String sqlname = s.getSQLTypeName();

Object[] attrs = s.getAttribute();

if (sqlname.equals ("HR.PERSON")

{

System.out.println ("ssn="+((BigDecimal)attrs[0]).intValue());

System.out.println ("name="+((String)attrs[1]));

System.out.println ("address="+((String)attrs[2]));

}

else if (sqlname.equals ("HR.STUDENT"))

{

System.out.println ("ssn="+((BigDecimal)attrs[0]).intValue());

System.out.println ("name="+((String)attrs[1]));

System.out.println ("address="+((String)attrs[2]));

System.out.println ("deptid="+((BigDecimal)attrs[3]).intValue());

System.out.println ("major="+((String)attrs[4]));

}

else if (sqlname.equals ("HR.PARTTIMESTUDENT"))

{

System.out.println ("ssn="+((BigDecimal)attrs[0]).intValue());

System.out.println ("name="+((String)attrs[1]));

System.out.println ("address="+((String)attrs[2]));

System.out.println ("deptid="+((BigDecimal)attrs[3]).intValue());

System.out.println ("major="+((String)attrs[4]));

System.out.println ("numHours="+((BigDecimal)attrs[5]).intValue());

}

else

Chapter 13

Object-Type Inheritance

13-27

throw new Exception ("Invalid type name: "+sqlname);

}

rset.close ();

stmt.close ();

conn.close ();

13.4.7 Inheritance Metadata Methods

Oracle JDBC drivers provide a set of metadata methods to access inheritance

properties. The inheritance metadata methods are defined in the

oracle.sql.StructDescriptor

and

oracle.jdbc.StructMetaData

classes.

The

StructMetaData

class provides inheritance metadata methods for subtype

attributes. The

getMetaData

method of the

StructDescriptor

class returns an

instance of

StructMetaData

of the type. The

StructMetaData

class contains the

following inheritance metadata methods:

13.5 About Describing an Object Type

Oracle JDBC includes functionality to retrieve information about a structured object

type regarding its attribute names and types. This is similar conceptually to retrieving

information from a result set about its column names and types, and in fact uses an

almost identical method.

This section covers the following topics:

• Functionality for Getting Object Metadata

• Retrieving Object Metadata

13.5.1 Functionality for Getting Object Metadata

The

oracle.sql.StructDescriptor

class includes functionality to retrieve metadata

about a structured object type. The

StructDescriptor

class has a

getMetaData

method with the same functionality as the standard

getMetaData

method available in

result set objects. It returns a set of attribute information, such as attribute names and

types. Call this method on a

StructDescriptor

object to get metadata about the

Oracle object type that the

StructDescriptor

object describes.

The signature of the

StructDescriptor

class

getMetaData

method is the same as the

signature specified for

getMetaData

in the standard

ResultSet

interface. The signature

is as follows:

ResultSetMetaData getMetaData() throws SQLException

However, this method actually returns an instance of

oracle.jdbc.StructMetaData

, a

class that supports structured object metadata in the same way that the standard

java.sql.ResultSetMetaData

interface specifies support for result set metadata.

The following method is also supported by

StructMetaData

String getOracleColumnClassName(int column) throws SQLException

This method returns the fully qualified name of the

oracle.sql.Datum

subclass whose

instances are manufactured if the

OracleResultSet

interface

getOracleObject

Chapter 13

About Describing an Object Type

13-28

method is called to retrieve the value of the specified attribute. For example,

oracle.sql.NUMBER

To use the

getOracleColumnClassName

method, you must cast the

ResultSetMetaData

object, which that was returned by the

getMetaData

method, to

StructMetaData

•

Note:

In all the preceding method signatures,

column

is something of a misnomer.

Where you specify a value of 4 for

column

, you really refer to the fourth attribute

of the object.

13.5.2 Retrieving Object Metadata

Use the following steps to obtain metadata about a structured object type:

1. Create or acquire a

StructDescriptor

instance that describes the relevant structured

object type.

2. Call the

getMetaData

method on the

StructDescriptor

instance.

3. Call the metadata getter methods,

getColumnName

getColumnType

, and

getColumnTypeName

, as desired.

Note:

If one of the structured object attributes is itself a structured object, repeat steps

1 through 3.

Example 13-1 Example

The following method shows how to retrieve information about the attributes of a structured

object type. This includes the initial step of creating a

StructDescriptor

instance.

// Print out the ADT's attribute names and types

void getAttributeInfo (Connection conn, String type_name) throws SQLException

{

// get the type descriptor

StructDescriptor desc = StructDescriptor.createDescriptor (type_name, conn);

// get type metadata

ResultSetMetaData md = desc.getMetaData ();

// get # of attrs of this type

int numAttrs = desc.length ();

// temporary buffers

String attr_name;

int attr_type;

String attr_typeName;

System.out.println ("Attributes of "+type_name+" :");

Chapter 13

About Describing an Object Type

13-29

for (int i=0; i<numAttrs; i++)

{

attr_name = md.getColumnName (i+1);

attr_type = md.getColumnType (i+1);

System.out.println (" index"+(i+1)+" name="+attr_name+" type="+attr_type);

// drill down nested object

if (attrType == OracleTypes.STRUCT)

{

attr_typeName = md.getColumnTypeName (i+1);

// recursive calls to print out nested object metadata

getAttributeInfo (conn, attr_typeName);

}

Chapter 13

About Describing an Object Type

13-30

Working with Large Objects and SecureFiles

Large Objects (LOBs) are a set of data types that are designed to hold large amounts of data.

This chapter describes how to use Java Database Connectivity (JDBC) to access and

manipulate LOBs and SecureFiles using either the data interface or the locator interface.

This chapter contains the following sections:

• The LOB Data Types

• Persistent LOBs

• Temporary LOBs

• Data Interface for LOBs

• Locator Interface for LOBs

• BFILEs

• JDBC Best Practices for LOB

14.1 The LOB Data Types

Oracle Database supports the following four LOB data types:

• Binary large object (BLOB)

This data type is used for unstructured binary data.

• Character large object (CLOB)

This data type is used for character data.

• National character large object (NCLOB)

This data type is used for national character data.

• BFILE

This data type is used for large binary data objects stored in operating system files,

outside of database tablespaces.

BLOBs, CLOBs, and NCLOBs are stored persistently in a database table and all operations

performed on these data types are under transaction control. You can also create temporary

LOBs of types BLOB, CLOB, or NCLOB to hold transient data. Both persistent and temporary

LOBs can be accessed and manipulated using the Data Interface and the Locator Interface.

BFILE is an Oracle proprietary data type that provides read-only access to data located

outside the database tablespaces on tertiary storage devices, such as hard disks, network

mounted files systems, CD-ROMs, PhotoCDs, and DVDs. BFILE data is not under

transaction control and is not stored by database backups.

The PL/SQL language supports the LOB data types and the JDBC interface allows passing

IN parameters to PL/SQL procedures or functions, and retrieval of OUT parameters or

returns.

14-1

See Also:

Introduction to Large Objects and SecureFiles

14.2 Persistent LOBs

A persistent LOB is a LOB instance that exists in a table row in the database. You can

store persistent LOBs as SecureFiles or BasicFiles.

See Also:

Persistent LOBs

SecureFiles is the default storage mechanism for LOBs in database tables. SecureFile

LOBs can only be created in tablespaces managed with Automatic Segment Space

Management (ASSM). Oracle strongly recommends SecureFiles for storing and

managing BLOBs, CLOBs, and NCLOBs.

Following Features of Oracle SecureFiles are transparently available to JDBC

programs through the existing APIs:

• Compression enables users to compress data to save disk space.

• Encryption provides an encryption facility that enables random read and write

operations of the encrypted data.

• Deduplication enables automatically detect duplicate LOB data and conserve

space by storing only one copy of the data.

isSecureFile Method

You can check whether or not your

BLOB

CLOB

data uses Oracle SecureFile storage.

To achieve this, use the following method from the

oracle.jdbc.OracleBlob

or the

oracle.jdbc.OracleClob

class:

public boolean isSecureFile() throws SQLException

If this method returns

true

, then your data uses SecureFile storage.

Both persistent and temporary LOBs can be accessed and manipulated using the Data

Interface and the Locator Interface.

See Also:

• Data Interface for LOBs

• Locator Interface for LOBs

Chapter 14

Persistent LOBs

14-2

14.3 Temporary LOBs

You can use temporary LOBs to store transient data. Temporary LOBs reside in either the

PGA memory or the temporary tablespace, depending on their size.

You can insert temporary LOBs into a regular database table. In such a case, a permanent

copy of the LOB is created and stored.

See Also:

Temporary LOBs

Creating a Temporary LOB

You create a temporary LOB with the static

createTemporary

method, defined in both the

oracle.sql.BLOB

and

oracle.sql.CLOB

classes. You can also create a temporary LOB by

using the connection factory methods available in JDBC 4.0. The Oracle JDBC drivers

implement the factory methods,

createBlob

createClob

, and

createNClob

in the

java.sql.Connection

interface to create temporary LOBs.

Freeing a Temporary LOB

You free a temporary LOB using the

freeTemporary

method. You can test whether a LOB is

temporary or not by calling the

isTemporary

method. If the LOB was created by calling the

createTemporary

method, then the

isTemporary

method returns

true

, else it returns

false

Starting with Oracle Database Release 21c, you do not need to check whether a LOB is

temporary or persistent before releasing the temporary LOB. If you call the

DBMS_LOB.FREETEMPORARY

procedure or the

OCILobFreeTemporary()

function on a LOB, it will

perform either of the following operations:

• For a temporary LOB, it will release the LOB.

• For a persistent LOB, it will do nothing (no-op).

Note:

• You must free any temporary LOBs before ending the session or call. If you do

not free a temporary LOB, then it will make the storage used by that LOB in the

database unavailable. Frequent failure to free temporary LOBs will result in

filling up temporary table space with unavailable LOB storage.

• The JDBC 4.0

free

method, present in the

java.sql.Blob

java.sql.Clob

, and

java.sql.NClob

interfaces, supersedes the

freeTemporary

method.

Both persistent and temporary LOBs can be accessed and manipulated using the Data

Interface and the Locator Interface.

Chapter 14

Temporary LOBs

14-3

See Also:

• Data Interface for LOBs

• Locator Interface for LOBs

14.4 Data Interface for LOBs

The data interface for LOBs includes a set of Java and OCI APIs that are extended to

work with LOB data types.

The data interface uses standard JDBC methods such as the

getString

method and

the

setBytes

method to read and write LOB data. Unlike the standard

java.sql.Blob

java.sql.Clob

, and

java.sql.NClob

interfaces, the data interface does not provide

random access capability, that is, it does not use LOB locator and cannot access data

beyond a size of 2 gigabytes.

See Also:

Data Interface for LOBs

You can use the data interface for LOBs to store and manipulate character data and

binary data in a LOB column as if it were stored in the corresponding legacy data

types like

VARCHAR2

LONG

RAW

, and so on. This section describes the following topics:

• Input

• Output

• CallableSatement and IN OUT Parameter

• Size Limitations

14.4.1 Input

The

setBytes

setBinaryStream

setString

setCharacterStream

, and

setAsciiStream

methods of the

PreparedStatement

interface are extended to

enhance the ability to work with

BLOB

CLOB

, and

NCLOB

target columns. If the length of

the data is known, then for better performance, use the versions of

setBinaryStream

setCharacterStream

methods that accept the data length as a parameter.

Note:

These methods do not work with

BFILE

data because it is read-only.

For the JDBC Oracle Call Interface (OCI) and Thin drivers, there is no limitation on the

size of the

byte

array,

String

, or the length specified for the stream functions, except

the limits imposed by the Java language.

Chapter 14

Data Interface for LOBs

14-4

Note:

In Java, the array size is limited to positive Java

int

or 2 gigabytes of size.

For the server-side internal driver, currently there is a limitation of 32767 bytes for operations

on SQL statements, such as an

INSERT

statement. This limitation does not apply for PL/SQL

statements. You can use the following workaround for an

INSERT

statement, where you can

wrap the LOB in a PL/SQL block:

BEGIN

INSERT id, c INTO clob_tab VALUES(?,?);

END;

Input Modes for LOBs

LOBs have the following three input modes:

• Direct binding

This binding is limited in size but most efficient. It places the data for all input columns

inline in the block of data sent to the server. All data, including multiple executions of a

batch, is sent in a single network operation.

• Stream binding

This binding places data at the end. It limits batch size to one and may require multiple

round trips to complete.

• LOB binding

This binding creates a temporary LOB, copies data to the LOB, and binds the LOB

locator. The temporary LOB is automatically freed after execution. The operation to

create the temporary LOB and then to writing to the LOB requires multiple round trips.

The input of the locators may be batched.

You must bear in mind the following automatic switching of the input mode for LOBs:

• For SQL statements:

– The

setBytes

and

setBinaryStream

methods use direct binding for data less than

32767 bytes.

– The

setBytes

and

setBinaryStream

methods use stream binding for data larger than

32767 bytes.

– Starting from JDBC 4.0, there are two forms of

setAsciiStream

setBinaryStream

and

setCharacterStream

methods. The form that accepts a

long

argument as

length, uses LOB binding for length larger than 2147483648. The form, where the

length is not specified, always uses LOB binding.

– The

setString

setCharacterStream

, and

setAsciiStream

methods use direct

binding for data smaller than 32767 characters.

– The

setString

setCharacterStream

, and

setAsciiStream

methods use stream

binding for data larger than 32766 characters.

• For PL/SQL statements:

– The

setBytes

and

setBinary

stream methods use direct binding for data less than

32767 bytes.

Chapter 14

Data Interface for LOBs

14-5

– The

setBytes

and

setBinaryStream

methods use LOB binding for data larger

than 32766 bytes.

– The

setString

setCharacterStream

, and

setAsciiStream

methods use

direct binding for data smaller than 32767 bytes in the database character set.

– The

setString

setCharacterStream

, and

setAsciiStream

methods use LOB

binding for data larger than 32766 bytes in the database character set.

• Forced conversion to LOBs

The

setBytesForBlob

and

setStringForClob

methods, present in the

oracle.jdbc.OraclePreparedStatement

interface, use LOB binding for any data

size.

Impact of Automatic Switching of Input Mode

The automatic switching of the input mode for large data has impact on certain

programs. Previously, you used to get

ORA-17157

errors for attempts to use the

setString

method for

String

values larger than 32766 characters. Now, depending

on the type of the target parameter, an error may occur while the statement is

executed or the operation may succeed.

Another impact is that the automatic switching may result in additional server-side

parsing to adapt to the change in the parameter type. This results in a performance

effect, if the data sizes vary above and below the limit for repeated executions of the

statement. Switching to the stream modes effects batching as well.

14.4.2 Output

The

getBytes

getBinaryStream

getString

getCharacterStream

, and

getAsciiStream

methods of the

ResultSet

and

CallableStatement

interfaces work

with

BLOB

CLOB

, and

BFILE

columns or

OUT

parameters. These methods work for any

LOB

of length less than 2147483648.

Note:

The

getString

and

getNString

methods cannot be used for retrieving BLOB

column values.

The data interface operates by accessing the

LOB

locators within the driver and is

transparent to the application programming interface.

You can read

BFILE

data, and read and write

BLOB

CLOB

data using the

defineColumnType

method. To read, use the

defineColumnType(nn,

Types.LONGVARBINARY)

or the

defineColumnType(nn,Types.LONGVARCHAR)

method on

the column. This produces a direct stream on the data as if it were a

LONG RAW

LONG

column, and gives the fastest read performance on LOBs.

You can also use LOB prefetching to reduce or eliminate any additional database

round trips.

Related Topics

• New Methods for National Character Set Type Data in JDK 6

Chapter 14

Data Interface for LOBs

14-6

• Locator Interface for LOBs

Locators are small data structures, which contain information that may be used to access

the actual data of the LOB. In a database table, the locator is stored directly in the table,

while the data may be in the table or in separate storage.

14.4.3 CallableSatement and IN OUT Parameter

If you have an

OUT

CLOB

parameter of a stored procedure and want to use the

setString

method for setting the value for this parameter, then for any

and

OUT

parameter, the binds

must be of the same type.

Note:

It is a PL/SQL requirement that the Java types used as input and output for an IN

OUT parameter must be the same. The automatic switching of types done by the

extensions described in this chapter may cause problems with this.

The automatic switching of the input mode causes problems if you are not sure of the data

sizes. For example, if you know that neither the input data nor the output data will ever be

larger than 32766 bytes, then you can use the

setString

method for the input parameter and

OUT

parameter as

Types.VARCHAR

and use the

getString

method for the output

parameter.

A better solution is to change the stored procedure to have separate

and

OUT

parameters.

That is, if you have the following piece of code in your application:

CREATE PROCEDURE clob_proc( c IN OUT CLOB );

then, change it to:

CREATE PROCEDURE clob_proc( c_in IN CLOB, c_out OUT CLOB );

Another workaround is to use a container block to make the call. The

clob_proc

procedure

can be wrapped with a Java String to use for the

prepareCall

statement, as follows:

"DECLARE c_temp; BEGIN c_temp := ?; clob_proc( c_temp); ? := c_temp; END;"

In either case, you can use the

setString

method on the first parameter and the

registerOutParameter

method with

Types.CLOB

on the second.

14.4.4 Size Limitations

You must be aware of the effect on the performance of the Java memory management

system due to creation of a very large

byte

array or a

String

. Read the information provided

by your Java virtual machine (JVM) vendor about the impact of very large data elements on

memory management, and consider using the stream interfaces instead.

Chapter 14

Data Interface for LOBs

14-7

14.5 Locator Interface for LOBs

Locators are small data structures, which contain information that may be used to

access the actual data of the LOB. In a database table, the locator is stored directly in

the table, while the data may be in the table or in separate storage.

See Also:

Locator Interface for LOBs

Starting from JDBC 4.0, you must use the

java.sql.Blob

java.sql.Clob

, and

java.sql.NClob

interfaces for performing read and write operations on LOBs. These

interfaces provide random access to the data in the LOB.

The Oracle implementation classes

oracle.sql.BLOB

oracle.sql.CLOB

, and

oracle.sql.NCLOB

store the locator and access the data with it. The

oracle.sql.BLOB

and

oracle.sql.CLOB

classes implement the

java.sql.Blob

and

java.sql.Clob

interfaces respectively. In

ojdbc6.jar

oracle.sql.NCLOB

implements

java.sql.NClob

, but in

ojdbc5.jar

, it implements the

java.sql.Clob

interface.

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.BLOB

and

oracle.sql.CLOB

classes are deprecated and replaced with the

oracle.jdbc.OracleBlob

and

oracle.jdbc.OracleClob

interfaces. Oracle

recommends you to use the methods available in the

java.sql

package,

where possible, for standard compatibility and methods available in the

oracle.jdbc

package for Oracle specific extensions. Refer to MoS Note

1364193.1 for more information about these interface.

In Oracle Database 21c, the Oracle JDBC drivers support the JDBC 4.0

java.sql.NClob

interface in

ojdbc11.jar

, which is compiled with JDK 11.

In contrast, the

oracle.sql.BFILE

is an Oracle extension, without a corresponding

java.sql

interface.

See Also:

JDBC Javadoc

Chapter 14

Locator Interface for LOBs

14-8

14.5.1 LOB prefetching

For the current release of JDBC drivers, the number of round trips is reduced by prefetching

the metadata such as the LOB length, the chunk size, and the beginning of the LOB data,

along with the locator during regular fetch operations.

If you select LOB columns into a result set, then some or all of the data is prefetched to the

client, when the locator is fetched. It saves the first round trip to retrieve data by deferring all

preceding operations until fetching from the locator.

Note:

• LOBs are not prefetched in abstract data types (ADTs) like STRUCTs and

ARRAYs. This behavior is exhibited even if you set the value of the

oracle.jdbc.defaultLobPrefetchSize

connection property. If the client

application performs an operation that depends on the value of a LOB, which is

embedded in such a data type, then additional round-trips are required to fetch

the value.

• The benefits of prefetching are more for small LOBs and less for larger LOBs.

• You must be aware of the possible memory consumption while setting large

LOB prefetch sizes in combination with a large row prefetch size and a large

number of LOB columns.

The default prefetch size is 32768. You can specify the prefetch size in bytes for BLOBs and

in characters for CLOBs, using the

oracle.jdbc.defaultLobPrefetchSize

connection

property. You can override the value of this property in the following two ways:

• At the statement level: By using the

oracle.jdbc.OracleStatement.setLobPrefetchSize(int)

method

• At the column level: By using the form of the

defineColumnType

method that takes

length as argument

See Also:

JDBC Javadoc

14.5.2 LOB Open and Close Operations

This section discusses how to open and close your LOBs.

This section discusses how to open and close your LOBs. The JDBC implementation of this

functionality is provided using the following methods available in the

oracle.sql.BLOB

and

oracle.sql.CLOB

interfaces:

•

void open (int mode)

•

void close()

Chapter 14

Locator Interface for LOBs

14-9

•

boolean isOpen()

Note:

You do not have to necessarily open and close your LOBs. You may choose

to open and close those for performance reasons.

See Also:

LOB Open and Close Operations

14.6 BFILEs

BFILEs are data objects stored in operating system files, outside the database

tablespaces. Data stored in a table column of type BFILE is physically located in an

operating system file, not in the database. The BFILE column stores a reference to the

operating system file.

BFILEs are read-only. The body of the data resides in the operating system (OS) file

system and you can write to BFILEs using only OS tools and commands. You can

create a BFILE for an existing external file by executing the appropriate SQL

statement using either JDBC APIs or any other way to execute SQL. However, using

SQL or JDBC, you cannot create an OS file that a BFILE refers to. Such OS files are

created only by an external process that has access to server file systems.

See Also:

BFILEs

This section describes how to use file locators to perform read and write operations on

BFILEs. This section covers the following topics:

• Retrieving BFILE Locators

• Inserting BFILES

Retrieving BFILE Locators

Both the BFILE data type and the

oracle.jdbc.OracleBfile

interface to work with the

BFILEs are Oracle proprietary. So, there is no standard interface for them. You must

use Oracle extensions for this type of data.

If you have a standard JDBC result set or callable statement object that includes

BFILE locators, then you can access the locators by using the standard result set

getObject

method. This method returns an

oracle.jdbc.OracleBfile

object.

You can also access the locators by casting your result set to

OracleResultSet

or your

callable statement to

OracleCallableStatement

and using the

getOracleObject

getBFILE

method.

Chapter 14

BFILEs

14-10

Note:

If you are using

getObject

getOracleObject

methods, then remember to cast

the output, as necessary.

Once you have a locator, you can access the BFILE data through the APIs present in the

oracle.jdbc.OracleBfile

class. These APIs are similar to the read methods of the

oracle.jdbc.OracleBfile

interface.

Inserting BFILES

You can use an instance of the

oracle.jdbc.OracleBfile

interface as input to a SQL

statement or to a PL/SQL procedure. You can achieve this by performing one of the following:

• Use the standard

setObject

method.

• Cast the statement to

OraclePreparedStatement

OracleCallableStatement

, and use

the

setOracleObject

setBFILE

method. These methods take the parameter index and

oracle.jdbc.OracleBfile

object as input.

Note:

– There is no standard

java.sql

interface for BFILEs.

– Use the

getBFILE

methods in the

OracleResultSet

and

OracleCallableStatement

interfaces to retrieve an

oracle.jdbc.OracleBfile

object. The

setBFILE

methods in

OraclePreparedStatement

and

OracleCallableStatement

interfaces

oracle.jdbc.OracleBfile

object as an argument. Use these

methods to write to a BFILE.

– Oracle recommends that you use the

getBFILE

setBFILE

, and

updateBFILE

methods instead of the

getBfile

setBfile

, and

updateBfile

methods. For example, use the

setBFILE

method instead of the

setBfile

method.

14.7 JDBC Best Practices for LOB

You can enhance the performance of your applications if you reduce the number of round-

trips to the database. This section describes how to minimize the number of round-trips to the

database.

If you know the maximum size of your LOB data, and you intend to perform read or write

operation on the entire LOB, then use the Data Interface following these guidelines:

• For read operations, define the LOB as character type or binary type using the

DefineColumnType

method.

• For write operations, bind the LOB as character type or binary type using the

setString

or the

setBytes

method.

Chapter 14

JDBC Best Practices for LOB

14-11

If you do not know the maximum size of your LOB data, then use the LOB APIs with

LOB prefetching for read operations. Also, define the LOB prefetch size to a value that

can accommodate majority of the LOB values in the column.

See Also:

LOB prefetching

Chapter 14

JDBC Best Practices for LOB

14-12

Using Oracle Object References

This chapter describes the standard Java Database Connectivity (JDBC) that let you access

and manipulate object references.

This section discusses the following topics:

• Oracle Extensions for Object References

• Retrieving and Passing an Object Reference

• Accessing and Updating Object Values Through an Object Reference

15.1 Oracle Extensions for Object References

Oracle supports the use of references to database objects. Oracle JDBC provides support for

object references as:

• Columns in a

SELECT

clause

• IN or OUT bind variables

• Attributes in an Oracle object

• Elements in a collection type object

In SQL, an object reference (

REF

) is strongly typed. For example, a reference to an

EMPLOYEE

object would be defined as an

EMPLOYEE REF

, not just a

REF

When you select an object reference, be aware that you are retrieving only a pointer to an

object, not the object itself. You have the choice of materializing the reference as a

java.sql.Ref

instance for portability, or materializing it as an instance of a custom Java class

that you have created in advance, which is strongly typed. Custom Java classes used for

object references are referred to as custom reference classes and must implement the

oracle.jdbc.OracleData

interface.

You can retrieve a

REF

instance through a result set or callable statement object, and pass an

updated

REF

instance back to the database through a prepared statement or callable

statement object. The

REF

class includes functionality to get and set underlying object

attribute values, and get the SQL base type name of the underlying object.

Custom reference classes include this same functionality, as well as having the advantage of

being strongly typed. This can help you find coding errors during compilation that might not

otherwise be discovered until run time.

15-1

Note:

• If you are using the

oracle.jdbc.OracleData

interface for custom object

classes, then you will presumably use

OracleData

for corresponding

custom reference classes as well. However, if you are using the standard

java.sql.SQLData

interface for custom object classes, then you can only

use weak Java types for references. The

SQLData

interface is for

mapping SQL object types only.

• You can create and retrieve

REF

objects in your JDBC application only by

running SQL statements. There is no JDBC-specific functionality for

creating and retrieving

REF

objects.

• You cannot have a reference to an array, even though arrays, like

objects, are structured types.

15.2 Retrieving and Passing an Object Reference

This section discusses JDBC functionality for retrieving and passing object references.

It covers the following topics:

• Retrieving an Object Reference from a Result Set

• Retrieving an Object Reference from a Callable Statement

• Passing an Object Reference to a Prepared Statement

15.2.1 Retrieving an Object Reference from a Result Set

To demonstrate how to retrieve object references, the following example first defines

an Oracle object type

ADDRESS

, which is then referenced in the

PEOPLE

table:

create type ADDRESS as object

(street_name VARCHAR2(30),

house_no NUMBER);

create table PEOPLE

(col1 VARCHAR2(30),

col2 NUMBER,

col3 REF ADDRESS);

The

ADDRESS

object type has two attributes: a street name and a house number. The

PEOPLE

table has three columns: a column for character data, a column for numeric

data, and a column containing a reference to an

ADDRESS

object.

To retrieve an object reference, follow these general steps:

1. Use a standard SQL

SELECT

statement to retrieve the reference from a database

table

REF

column.

2. Use

getRef

to get the address reference from the result set into an

OracleRef

instance.

3. Let

Address

be the Java custom class corresponding to the SQL object type

ADDRESS

Chapter 15

Retrieving and Passing an Object Reference

15-2

4. Add the correspondence between the Java class

Address

and the SQL type

ADDRESS

your type map.

5. Use the

getObject

method to retrieve the contents of the

Address

reference. Cast the

output to

Address

The

PEOPLE

database table is defined earlier in this section. The code for the preceding steps,

except the step of adding

Address

to the type map, is as follows:

ResultSet rs = stmt.executeQuery("SELECT col3 FROM PEOPLE");

while (rs.next())

{

OracleRef ref = rs.getRef(1);

Address a = (Address)ref.getObject();

}

Note:

In the preceding code,

stmt

is a previously defined statement object.

15.2.2 Retrieving an Object Reference from a Callable Statement

To retrieve an object reference as an

OUT

parameter in PL/SQL blocks, you must register the

bind type for your

OUT

parameter.

1. Cast your callable statement to

OracleCallableStatement

, as follows:

OracleCallableStatement ocs =

(OracleCallableStatement)conn.prepareCall("{? = call func()}");

2. Register the

OUT

parameter with the following form of the

registerOutParameter

method:

ocs.registerOutParameter (int param_index, int sql_type, String sql_type_name);

param_index

is the parameter index and

sql_type

is the SQL type code. The

sql_type_name

is the name of the structured object type that this reference is used for.

For example, if the

OUT

parameter is a reference to an

ADDRESS

object, then

ADDRESS

the

sql_type_name

that should be passed in.

3. Run the call, as follows:

ocs.execute();

15.2.3 Passing an Object Reference to a Prepared Statement

Pass an object reference to a prepared statement in the same way as you would pass any

other SQL type. Use either the

setObject

method or the

setREF

method of a prepared

statement object.

Use a prepared statement to update an address reference based on

ROWID

, as follows:

PreparedStatement pstmt =

conn.prepareStatement ("update PEOPLE set ADDR_REF = ? where ROWID = ?");

pstmt.setRef (1, addr_ref);

pstmt.setRowId (2, rowid);

Chapter 15

Retrieving and Passing an Object Reference

15-3

15.3 Accessing and Updating Object Values Through an

Object Reference

You can use the

Ref

object

setObject

method to update the value of an object in the

database through an object reference. To do this, you must first retrieve the reference

to the database object and create a Java object that corresponds to the database

object.

For example, you can use the code in the "Retrieving and Passing an Object

Reference" section to retrieve the reference to a database

ADDRESS

object, as shown in

the following code snippet:

ResultSet rs = stmt.executeQuery("SELECT col3 FROM PEOPLE");

if (rs.next())

{

Ref ref = rs.getRef(1);

Address a = (Address)ref.getObject();

}

Then, you can create a Java

Address

object that corresponds to the database

ADDRESS

object. Use the

setObject

method of the

Ref

interface to set the value of the database

object, as follows:

Address addr = new Address(...);

ref.setObject(addr);

Here, the

setValue

method updates the database

ADDRESS

object immediately.

Related Topics

• Retrieving and Passing an Object Reference

Chapter 15

Accessing and Updating Object Values Through an Object Reference

15-4

Working with Oracle Collections

This chapter describes Oracle extensions to standard Java Database Connectivity (JDBC)

that let you access and manipulate Oracle collections, which map to Java arrays, and their

data. The following topics are discussed:

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.ARRAY

class is

deprecated and replaced with the

oracle.jdbc.OracleArray

interface, which is a

part of the

oracle.jdbc

package. Oracle recommends you to use the methods

available in the

java.sql

package, where possible, for standard compatibility and

methods available in the

oracle.jdbc

package for Oracle specific extensions. Refer

to MoS Note 1364193.1 for more information about the

oracle.jdbc.OracleArray

interface.

• Oracle Extensions for Collections

• Overview of Collection Functionality

• ARRAY Performance Extension Methods

• Creating and Using Arrays

• Using a Type Map to Map Array Elements

16.1 Oracle Extensions for Collections

This section covers the following topics:

• Overview of Oracle Collections

• Choices in Materializing Collections

• Creating Collections

• Creating Multilevel Collection Types

16.1.1 Overview of Oracle Collections

An Oracle collection, either a variable array (VARRAY) or a nested table in the database,

maps to an array in Java. JDBC 2.0 arrays are used to materialize Oracle collections in Java.

The terms collection and array are sometimes used interchangeably. However, collection is

more appropriate on the database side and array is more appropriate on the JDBC

application side.

Oracle supports only named collections, where you specify a SQL type name to describe a

type of collection. JDBC enables you to use arrays as any of the following:

• Columns in a

SELECT

clause

16-1

•

OUT

bind variables

• Attributes in an Oracle object

• Elements of other arrays

16.1.2 Choices in Materializing Collections

In your application, you have the choice of materializing a collection as an instance of

the

oracle.sql.ARRAY

class, which is weakly typed, or materializing it as an instance

of a custom Java class that you have created in advance, which is strongly typed.

Custom Java classes used for collections are referred to as custom collection classes.

A custom collection class must implement the Oracle

oracle.jdbc.OracleData

interface. In addition, the custom class or a companion class must implement

oracle.jdbc.OracleDataFactory

. The standard

java.sql.SQLData

interface is for

mapping SQL object types only.

The

oracle.sql.ARRAY

class implements the standard

java.sql.Array

interface.

The

ARRAY

class includes functionality to retrieve the array as a whole, retrieve a

subset of the array elements, and retrieve the SQL base type name of the array

elements. However, you cannot write to the array, because there are no setter

methods.

Custom collection classes, as with the

ARRAY

class, enable you to retrieve all or part of

the array and get the SQL base type name. They also have the advantage of being

strongly typed, which can help you find coding errors during compilation that might not

otherwise be discovered until run time.

Note:

There is no difference in the code between accessing VARRAYs and

accessing nested tables.

ARRAY

class methods can determine if they are

being applied to a VARRAY or nested table, and respond by taking the

appropriate actions.

16.1.3 Creating Collections

Because Oracle supports only named collections, you must declare a particular

VARRAY

type name or nested table type name. VARRAY and nested table are not types

themselves, but categories of types.

A SQL type name is assigned to a collection when you create it using the SQL

CREATE

TYPE

statement:

CREATE TYPE <sql_type_name> AS <datatype>;

A VARRAY is an array of varying size. It has an ordered set of data elements, and all

the elements are of the same data type. Each element has an index, which is a

number corresponding to the position of the element in the VARRAY. The number of

elements in a VARRAY is the size of the VARRAY. You must specify a maximum size

when you declare the

VARRAY

type. For example:

CREATE TYPE myNumType AS VARRAY(10) OF NUMBER;

Chapter 16

Oracle Extensions for Collections

16-2

This statement defines

myNumType

as a SQL type name that describes a VARRAY of

NUMBER

values that can contain no more than 10 elements.

A nested table is an unordered set of data elements, all of the same data type. The database

stores a nested table in a separate table which has a single column, and the type of that

column is a built-in type or an object type. If the table is an object type, then it can also be

viewed as a multi-column table, with a column for each attribute of the object type. You can

create a nested table as follows:

CREATE TYPE myNumList AS TABLE OF integer;

This statement identifies

myNumList

as a SQL type name that defines the table type used for

the nested tables of the type

INTEGER

16.1.4 Creating Multilevel Collection Types

The most common way to create a new multilevel collection type in JDBC is to pass the SQL

CREATE TYPE

statement to the

execute

method of the

java.sql.Statement

class. The

following code creates a one-level nested table,

first_level

, and a two- levels nested table,

second_level

Connection conn = .... // make a database

// connection

Statement stmt = conn.createStatement(); // open a database

// cursor

stmt.execute("CREATE TYPE first_level AS TABLE OF NUMBER"); // create a nested

// table of number

stmt.execute("CREATE TYPE second_level AS TABLE OF first_level"); // create a

// two-levels nested table

... // other operations here

stmt.close(); // release the

// resource

conn.close(); // close the

// database connection

Once the multilevel collection types have been created, they can be used as both columns of

a base table as well as attributes of a object type.

Note:

Multilevel collection types are available only for Oracle9i and later.

16.2 Overview of Collection Functionality

You can obtain collection data in an array instance through a result set or callable statement

and pass it back as a bind variable in a prepared statement or callable statement.

The

oracle.sql.ARRAY

class, which implements the standard

java.sql.Array

interface,

provides the necessary functionality to access and update the data of an Oracle collection.

This section covers Array Getter and Setter Methods. Use the following result set, callable

statement, and prepared statement methods to retrieve and pass collections as Java arrays.

Chapter 16

Overview of Collection Functionality

16-3

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.ARRAY

class is deprecated and replaced with the

oracle.jdbc.OracleArray

interface, which is a part of the

oracle.jdbc

package. Oracle recommends

you to use the methods available in the

java.sql

package, where possible,

for standard compatibility and methods available in the

oracle.jdbc

package

for Oracle specific extensions. Refer to MoS Note 1364193.1 for more

information about the

oracle.jdbc.OracleArray

interface.

Result Set and Callable Statement Getter Methods

The

OracleResultSet

and

OracleCallableStatement

interfaces support

getARRAY

and

getArray

methods to retrieve

ARRAY

objects as output parameters, either as

oracle.sql.ARRAY

instances or

java.sql.Array

instances. You can also use the

getObject

method. These methods take as input a

String

column name or

int

column index.

Note:

The Oracle JDBC drivers cache array and structure descriptors. This

provides enormous performance benefits; however, it means that if you

change the underlying type definition of an array type in the database, the

cached descriptor for that array type will become stale and your application

will receive a

SQLException

Prepared and Callable Statement Setter Methods

The

OraclePreparedStatement

and

OracleCallableStatement

classes support

setARRAY

and

setArray

methods to take updated

ARRAY

objects as bind variables and

pass them to the database. You can also use the

setObject

method. These methods

take as input a

String

parameter name or

int

parameter index as well as an

oracle.sql.ARRAY

instance or a

java.sql.Array

instance.

16.3 ARRAY Performance Extension Methods

This section discusses the following topics:

• About Accessing oracle.sql.ARRAY Elements as Arrays of Java Primitive Types

• ARRAY Automatic Element Buffering

• ARRAY Automatic Indexing

16.3.1 About Accessing oracle.sql.ARRAY Elements as Arrays of Java

Primitive Types

The

oracle.sql.ARRAY

class contains methods that return array elements as Java

primitive types. These methods enable you to access collection elements more

Chapter 16

ARRAY Performance Extension Methods

16-4

efficiently than accessing them as

Datum

instances and then converting each

Datum

instance

to its Java primitive value.

Note:

These specialized methods of the

oracle.sql.ARRAY

class are restricted to numeric

collections.

Each method using the first signature returns collection elements as an

XXX[]

, where

XXX

is a

Java primitive type. Each method using the second signature returns a slice of the collection

containing the number of elements specified by

count

, starting at the

index

location.

16.3.2 ARRAY Automatic Element Buffering

Oracle JDBC driver provides public methods to enable and disable buffering of

ARRAY

contents.

The following methods are included with the

oracle.sql.ARRAY

class:

•

setAutoBuffering

•

getAutoBuffering

It is advisable to enable auto-buffering in a JDBC application when the

ARRAY

elements will be

accessed more than once by the

getAttributes

and

getArray

methods, presuming the

ARRAY

data is able to fit into the Java Virtual Machine (JVM) memory without overflow.

Note:

Buffering the converted elements may cause the JDBC application to consume a

significant amount of memory.

When you enable auto-buffering, the

oracle.sql.ARRAY

object keeps a local copy of all the

converted elements. This data is retained so that a second access of this information does

not require going through the data format conversion process.

16.3.3 ARRAY Automatic Indexing

If an array is in auto-indexing mode, then the array object maintains an index table to hasten

array element access.

The

oracle.sql.ARRAY

class contains the following methods to support automatic array-

indexing:

•

setAutoIndexing(boolean)

•

setAutoIndexing(boolean, int)

By default, auto-indexing is not enabled. For a JDBC application, enable auto-indexing for

ARRAY

objects if random access of array elements may occur through the

getArray

and

getResultSet

methods.

Chapter 16

ARRAY Performance Extension Methods

16-5

16.4 Creating and Using Arrays

This section discusses how to create array objects and how to retrieve and pass

collections as array objects, including the following topics.

• Creating ARRAY Objects

• Retrieving an Array and Its Elements

• Passing Arrays to Statement Objects

16.4.1 Creating ARRAY Objects

Note:

Oracle JDBC does not support the JDBC 4.0 method

createArrayOf

method

java.sql.Connection

interface. This method only allows anonymous

array types, while all Oracle array types are named. Use the Oracle specific

method

oracle.jdbc.OracleConnection.createARRAY

instead.

This section describes how to create

ARRAY

objects. This section covers the following

topics:

• Steps in Creating ARRAY Objects

• Example 16-1

Steps in Creating ARRAY Objects

Starting from Oracle Database 11g Release 1, you can use the

createARRAY

factory

method of

oracle.jdbc.OracleConnection

interface to create an array object. The

factory method for creating arrays has been defined as follows:

public ARRAY createARRAY(java.lang.String typeName,java.lang.Object

elements)throws SQLException

where,

typeName

is the name of the SQL type of the created object and

elements

the elements of the created object.

Perform the following to create an array:

1. Create a collection with the

CREATE

TYPE

statement as follows:

CREATE TYPE elements AS varray(22) OF NUMBER(5,2);

The two possibilities for the contents of

elements

are:

• An array of Java primitives. For example,

int[]

• An array of Java objects, such as

xxx[]

, where

xxx

is the name of a Java

class. For example,

Integer[]

Chapter 16

Creating and Using Arrays

16-6

Note:

The

setARRAY

setArray

, and

setObject

methods of the

OraclePreparedStatement

class take an object of the type

oracle.sql.ARRAY

as an argument, not an array of objects.

2. Construct the

ARRAY

object by passing the Java string specifying the user-defined SQL

type name of the array and a Java object containing the individual elements you want the

array to contain.

ARRAY array = oracle.jdbc.OracleConnection.createARRAY(sql_type_name, elements);

Note:

The name of the collection type is not the same as the type name of the elements.

For example:

CREATE TYPE person AS object

(c1 NUMBER(5), c2 VARCHAR2(30));

CREATE TYPE array_of_persons AS varray(10)

OF person;

In the preceding statements, the name of the collection type is

ARRAY_OF_PERSON

The SQL type name of the collection elements is

PERSON

Example 16-1 Creating Multilevel Collections

As with single-level collections, the JDBC application can create an

oracle.sql.ARRAY

instance to represent a multilevel collection, and then send the instance to the database. The

same

createARRAY

factory method you use to create single-level collections, can be used to

create multilevel collections as well. To create a single-level collection, the elements are a

one dimensional Java array, while to create a multilevel collection, the elements can be either

an array of

oracle.sql.ARRAY[]

elements or a nested Java array or the combinations.

The following code shows how to create collection types with a nested Java array:

// prepare the multilevel collection elements as a nested Java array

int[][][] elements = { {{1}, {1, 2}}, {{2}, {2, 3}}, {{3}, {3, 4}} };

// create the ARRAY using the factory method

ARRAY array = oracle.jdbc.OracleConnection.createARRAY(sql_type_name, elements);

16.4.2 Retrieving an Array and Its Elements

This section first discusses how to retrieve an

ARRAY

instance as a whole from a result set,

and then how to retrieve the elements from the

ARRAY

instance. This section covers the

following topics:

• About Retrieving the Array

• Data Retrieval Methods

• Comparing the Data Retrieval Methods

Chapter 16

Creating and Using Arrays

16-7

• Retrieving Elements of a Structured Object Array According to a Type Map

• Retrieving a Subset of Array Elements

• Retrieving Array Elements into an oracle.sql.Datum Array

• About Accessing Multilevel Collection Elements

16.4.2.1 About Retrieving the Array

You can retrieve a SQL array from a result set by casting the result set to

OracleResultSet

and using the

getARRAY

method, which returns an

oracle.sql.ARRAY

object. If you want to avoid casting the result set, then you can get

the data with the standard

getObject

method specified by the

java.sql.ResultSet

interface and cast the output to

oracle.sql.ARRAY

16.4.2.2 Data Retrieval Methods

Once you have an

ARRAY

object, you can retrieve the data using one of these three

overloaded methods of the

oracle.sql.ARRAY

class:

•

getArray

•

getOracleArray

•

getResultSet

Oracle also provides methods that enable you to retrieve all the elements of an array,

or a subset.

Note:

In case you are working with an array of structured objects, Oracle provides

versions of these three methods that enable you to specify a type map so

that you can choose how to map the objects to Java.

getOracleArray

The

getOracleArray

method is an Oracle-specific extension that is not specified in the

standard

Array

interface. The

getOracleArray

method retrieves the element values of

the array into a

Datum[]

array. The elements are of the

oracle.sql.*

data type

corresponding to the SQL type of the data in the original array.

For an array of structured objects, this method will use

oracle.jdbc.OracleStruct

instances for the elements.

Oracle also provides a

getOracleArray(index,count)

method

to get a subset of the

array elements.

getResultSet

The

getResultSet

method returns a result set that contains elements of the array

designated by the

ARRAY

object. The result set contains one row for each array

element, with two columns in each row. The first column stores the index into the array

for that element, and the second column stores the element value. In the case of

VARRAYs, the index represents the position of the element in the array. In the case of

Chapter 16

Creating and Using Arrays

16-8

nested tables, which are by definition unordered, the index reflects only the return order of

the elements in the particular query.

Oracle recommends using

getResultSet

when getting data from nested tables. Nested

tables can have an unlimited number of elements. The

ResultSet

object returned by the

method initially points at the first row of data. You get the contents of the nested table by

using the

method and the appropriate

getXXX

method. In contrast,

getArray

returns the

entire contents of the nested table at one time.

The

getResultSet

method uses the default type map of the connection to determine the

mapping between the SQL type of the Oracle object and its corresponding Java data type. If

you do not want to use the default type map of the connection, another version of the

method,

getResultSet(map)

, enables you to specify an alternate type map.

Oracle also provides the

getResultSet(index,count)

and

getResultSet(index,count,map)

methods to retrieve a subset of the array elements.

getArray

The

getArray

method is a standard JDBC method that returns the array elements as a

java.lang.Object

, which you can cast as appropriate. The elements are converted to the

Java types corresponding to the SQL type of the data in the original array.

Oracle also provides a

getArray(index,count)

method to retrieve a subset of the array

elements.

16.4.2.3 Comparing the Data Retrieval Methods

If you use

getOracleArray

to return the array elements, then the use by that method of

oracle.sql.Datum

instances avoids the expense of data conversion from SQL to Java. The

non-character data inside the instance of a

Datum

class or any of its subclass remains in raw

SQL format.

If you use

getResultSet

to return an array of primitive data types, then the JDBC driver

returns a

ResultSet

object that contains, for each element, the index into the array for the

element and the element value. For example:

ResultSet rset = intArray.getResultSet();

In this case, the result set contains one row for each array element, with two columns in each

row. The first column stores the index into the array and the second column stores the

element value.

If the elements of an array are of a SQL type that maps to a Java type, then

getArray

returns

an array of elements of this Java type. The return type of the

getArray

method is

java.lang.Object

. Therefore, the result must be cast before it can be used.

BigDecimal[] values = (BigDecimal[]) intArray.getArray();

Here

intArray

is an

oracle.sql.ARRAY

, corresponding to a VARRAY of type

NUMBER

. The

values

array contains an array of elements of type

java.math.BigDecimal

, because the SQL

NUMBER

data type maps to Java

BigDecimal

, by default, according to Oracle JDBC drivers.

Chapter 16

Creating and Using Arrays

16-9

Note:

Using

BigDecimal

is a resource-intensive operation in Java. Because Oracle

JDBC maps numeric SQL data to

BigDecimal

by default, using

getArray

may impact performance, and is not recommended for numeric collections.

16.4.2.4 Retrieving Elements of a Structured Object Array According to a Type

Map

By default, if you are working with an array whose elements are structured objects,

and you use

getArray

getResultSet

, then the Oracle objects in the array will be

mapped to their corresponding Java data types according to the default mapping. This

is because these methods use the default type map of the connection to determine the

mapping.

However, if you do not want default behavior, then you can use the

getArray(map)

getResultSet(map)

method to specify a type map that contains alternate mappings. If

there are entries in the type map corresponding to the Oracle objects in the array, then

each object in the array is mapped to the corresponding Java type specified in the type

map. For example:

Object[] object = (Object[])objArray.getArray(map);

Where

objArray

is an

oracle.sql.ARRAY

object and

map

is a

java.util.Map

object.

If the type map does not contain an entry for a particular Oracle object, then the

element is returned as an

oracle.jdbc.OracleStruct

object.

The

getResultSet(map)

method behaves similarly to the

getArray(map)

method.

Related Topics

• Using a Type Map to Map Array Elements

16.4.2.5 Retrieving a Subset of Array Elements

If you do not want to retrieve the entire contents of an array, then you can use

signatures of

getArray

getResultSet

, and

getOracleArray

that let you retrieve a

subset. To retrieve a subset of the array, pass in an index and a count to indicate

where in the array you want to start and how many elements you want to retrieve. As

previously described, you can specify a type map or use the default type map for your

connection to convert to Java types. For example:

Object object = arr.getArray(index, count, map);

Object object = arr.getArray(index, count);

Similar examples using

getResultSet

are:

ResultSet rset = arr.getResultSet(index, count, map);

ResultSet rset = arr.getResultSet(index, count);

A similar example using

getOracleArray

is:

Datum[] arr = arr.getOracleArray(index, count);

Chapter 16

Creating and Using Arrays

16-10

Where

arr

is an

oracle.sql.ARRAY

object,

index

is type

long

count

is type

int

, and

map

is a

java.util.Map

object.

Note:

There is no performance advantage in retrieving a subset of an array, as opposed

to the entire array.

16.4.2.6 Retrieving Array Elements into an oracle.sql.Datum Array

Use

getOracleArray

to return an

oracle.sql.Datum[]

array. The elements of the returned

array is of

oracle.sql.*

type that correspond to the SQL data type of the elements of the

original array. For example:

Datum arraydata[] = arr.getOracleArray();

arr

is an

oracle.sql.ARRAY

object.

The following example assumes that a connection object

conn

and a statement object

stmt

have already been created. In the example, an array with the SQL type name

NUM_ARRAY

created to store a VARRAY of

NUMBER

data. The

NUM_ARRAY

is in turn stored in a table

VARRAY_TABLE

A query selects the contents of the

VARRAY_TABLE

. The result set is cast to

OracleResultSet

The

getARRAY

method is applied to it to retrieve the array data into

my_array

, which is an

oracle.sql.ARRAY

object.

Because

my_array

is of type

oracle.sql.ARRAY

, you can apply the methods

getSQLTypeName

and

getBaseType

to it to return the name of the SQL type of each element in the array and its

integer code.

The program then prints the contents of the array. Because the contents of

NUM_ARRAY

are of

the SQL data type

NUMBER

, the elements of

my_array

are of the type,

BigDecimal

. Before you

can use the elements, they must first be cast to

BigDecimal

. In the

for

loop, the individual

values of the array are cast to

BigDecimal

and printed to standard output.

stmt.execute ("CREATE TYPE num_varray AS VARRAY(10) OF NUMBER(12, 2)");

stmt.execute ("CREATE TABLE varray_table (col1 num_varray)");

stmt.execute ("INSERT INTO varray_table VALUES (num_varray(100, 200))");

ResultSet rs = stmt.executeQuery("SELECT * FROM varray_table");

ARRAY my_array = ((OracleResultSet)rs).getARRAY(1);

// return the SQL type names, integer codes,

// and lengths of the columns

System.out.println ("Array is of type " + array.getSQLTypeName());

System.out.println ("Array element is of type code " + array.getBaseType());

System.out.println ("Array is of length " + array.length());

// get Array elements

BigDecimal[] values = (BigDecimal[]) my_array.getArray();

for (int i=0; i<values.length; i++)

{

BigDecimal out_value = (BigDecimal) values[i];

Chapter 16

Creating and Using Arrays

16-11

System.out.println(">> index " + i + " = " + out_value.intValue());

}

Note that if you use

getResultSet

to obtain the array, then you must would first get the

result set object, and then use the

method to iterate through it. Notice the use of

the parameter indexes in the

getInt

method to retrieve the element index and the

element value.

ResultSet rset = my_array.getResultSet();

while (rset.next())

{

// The first column contains the element index and the

// second column contains the element value

System.out.println(">> index " + rset.getInt(1)+" = " + rset.getInt(2));

}

16.4.2.7 About Accessing Multilevel Collection Elements

The

oracle.sql.ARRAY

class provides three methods, which are overloaded, to access

collection elements. The JDBC drivers extend these methods to support multilevel

collections. These methods are:

•

getArray

method

•

getOracleArray

method

•

getResultSet

method

The

getArray

method returns a Java array that holds the collection elements. The

array element type is determined by the collection element type and the JDBC default

conversion matrix.

For example, the

getArray

method returns a

java.math.BigDecimal

array for

collection of SQL

NUMBER

. The

getOracleArray

method returns a

Datum

array that

holds the collection elements in

Datum

format. For multilevel collections, the

getArray

and

getOracleArray

methods both return a Java array of

oracle.sql.ARRAY

elements.

The

getResultSet

method returns a

ResultSet

object that wraps the multilevel

collection elements. For multilevel collections, the JDBC applications use the

getObject

getARRAY

, or

getArray

method of the

ResultSet

class to access the

collection elements as instances of

oracle.sql.ARRAY

The following code shows how to use the

getOracleArray

getArray

, and

getResultSet

methods:

Connection conn = ...; // make a JDBC connection

Statement stmt = conn.createStatement ();

ResultSet rset = stmt.executeQuery ("select col2 from tab2 where idx=1");

while (rset.next())

{

ARRAY varray3 = (ARRAY) rset.getObject (1);

Object varrayElems = varray3.getArray (1);

// access array elements of "varray3"

Datum[] varray3Elems = (Datum[]) varrayElems;

for (int i=0; i<varray3Elems.length; i++)

{

ARRAY varray2 = (ARRAY) varray3Elems[i];

Chapter 16

Creating and Using Arrays

16-12

Datum[] varray2Elems = varray2.getOracleArray();

// access array elements of "varray2"

for (int j=0; j<varray2Elems.length; j++)

{

ARRAY varray1 = (ARRAY) varray2Elems[j];

ResultSet varray1Elems = varray1.getResultSet();

// access array elements of "varray1"

while (varray1Elems.next())

System.out.println ("idx="+varray1Elems.getInt(1)+"

value="+varray1Elems.getInt(2));

}

rset.close ();

stmt.close ();

conn.close ();

16.4.3 Passing Arrays to Statement Objects

This section discusses how to pass arrays to prepared statement objects or callable

statement objects.

Passing an Array to a Prepared Statement

Pass an array to a prepared statement as follows.

Note:

you can use arrays as either

OUT

bind variables.

1. Define the array that you want to pass to the prepared statement as an

oracle.sql.ARRAY

object.

ARRAY array = oracle.jdbc.OracleConnection.createARRAY(sql_type_name, elements);

sql_type_name

is a Java string specifying the user-defined SQL type name of the array

and

elements

is a

java.lang.Object

containing a Java array of the elements.

2. Create a

java.sql.PreparedStatement

object containing the SQL statement to be run.

3. Cast your prepared statement to

OraclePreparedStatement

, and use

setARRAY

to pass

the array to the prepared statement.

(OraclePreparedStatement)stmt.setARRAY(parameterIndex, array);

parameterIndex

is the parameter index and

array

is the

oracle.sql.ARRAY

object you

constructed previously.

4. Run the prepared statement.

Passing an Array to a Callable Statement

To retrieve a collection as an

OUT

parameter in PL/SQL blocks, perform the following to

OUT

parameter.

Chapter 16

Creating and Using Arrays

16-13

1. Cast your callable statement to

OracleCallableStatement

, as follows:

OracleCallableStatement ocs = (OracleCallableStatement)conn.prepareCall("{?

= call func()}");

2. Register the

OUT

parameter with the following form of the

registerOutParameter

method:

ocs.registerOutParameter

(int param_index, int sql_type, string sql_type_name);

param_index

is the parameter index,

sql_type

is the SQL type code, and

sql_type_name

is the name of the array type. In this case, the

sql_type

OracleTypes.ARRAY

3. Run the call, as follows:

ocs.execute();

4. Get the value, as follows:

oracle.sql.ARRAY array = ocs.getARRAY(1);

16.5 Using a Type Map to Map Array Elements

If your array contains Oracle objects, then you can use a type map to associate the

objects in the array with the corresponding Java class. If you do not specify a type

map, or if the type map does not contain an entry for a particular Oracle object, then

each element is returned as an

oracle.jdbc.OracleStruct

object.

If you want the type map to determine the mapping between the Oracle objects in the

array and their associated Java classes, then you must add an appropriate entry to the

map.

The following example illustrates how you can use a type map to map the elements of

an array to a custom Java object class. In this case, the array is a nested table. The

example begins by defining an

EMPLOYEE

object that has a name attribute and

employee number attribute.

EMPLOYEE_LIST

is a nested table type of

EMPLOYEE

objects.

Then an

EMPLOYEE_TABLE

is created to store the names of departments within a

corporation and the employees associated with each department. In the

EMPLOYEE_TABLE

, the employees are stored in the form of

EMPLOYEE_LIST

tables.

stmt.execute("CREATE TYPE EMPLOYEE AS OBJECT

(EmpName VARCHAR2(50),EmpNo INTEGER))");

stmt.execute("CREATE TYPE EMPLOYEE_LIST AS TABLE OF EMPLOYEE");

stmt.execute("CREATE TABLE EMPLOYEE_TABLE (DeptName VARCHAR2(20),

Employees EMPLOYEE_LIST) NESTED TABLE Employees STORE AS ntable1");

stmt.execute("INSERT INTO EMPLOYEE_TABLE VALUES ("SALES", EMPLOYEE_LIST

(EMPLOYEE('Susan Smith', 123), EMPLOYEE('Lee Brown', 124)))");

If you want to retrieve all the employees belonging to the

SALES

department into an

array of instances of the custom object class

EmployeeObj

, then you must add an entry

to the type map to specify mapping between the

EMPLOYEE

SQL type and the

EmployeeObj

custom object class.

To do this, first create your statement and result set objects, then select the

EMPLOYEE_LIST

associated with the

SALES

department into the result set. Cast the

Chapter 16

Using a Type Map to Map Array Elements

16-14

result set to

OracleResultSet

so you can use the

getARRAY

method to retrieve the

EMPLOYEE_LIST

into an

ARRAY

object (

employeeArray

in the following example).

The

EmployeeObj

custom object class in this example implements the

SQLData

interface.

Statement s = conn.createStatement();

OracleResultSet rs = (OracleResultSet)s.executeQuery

("SELECT Employees FROM employee_table WHERE DeptName = 'SALES'");

// get the array object

ARRAY employeeArray = ((OracleResultSet)rs).getARRAY(1);

Now that you have the

EMPLOYEE_LIST

object, get the existing type map and add an entry that

maps the

EMPLOYEE

SQL type to the

EmployeeObj

Java type.

// add type map entry to map SQL type

// "EMPLOYEE" to Java type "EmployeeObj"

Map map = conn.getTypeMap();

map.put("EMPLOYEE", Class.forName("EmployeeObj"));

Next, retrieve the SQL

EMPLOYEE

objects from the

EMPLOYEE_LIST

. To do this, call the

getArray

method of the

employeeArray

array object. This method returns an array of objects.

The

getArray

method returns the

EMPLOYEE

objects into the

employees

object array.

// Retrieve array elements

Object[] employees = (Object[]) employeeArray.getArray();

Finally, create a loop to assign each of the

EMPLOYEE

SQL objects to the

EmployeeObj

Java

object

emp

// Each array element is mapped to EmployeeObj object.

for (int i=0; i<employees.length; i++)

{

EmployeeObj emp = (EmployeeObj) employees[i];

...

}

Chapter 16

Using a Type Map to Map Array Elements

16-15

Result Set

Standard Java Database Connectivity (JDBC) features in Java Development Kit (JDK)

include enhancements to result set functionality, such as processing forward or backward,

positioning relatively or absolutely, seeing changes to the database made internally or

externally, and updating result set data and then copying the changes to the database.

This chapter discusses the following topics:

• Oracle JDBC Implementation Overview for Result Set Support

• Resultset Limitations and Downgrade Rules

• About Avoiding Update Conflicts

• Row Fetch Size

• About Refetching Rows

• About Viewing Database Changes Made Internally and Externally

17.1 Oracle JDBC Implementation Overview for Result Set

Support

This section discusses key aspects of the Oracle JDBC implementation of result set support

for scrollability, through use of a client-side cache, and for updatability, through use of

ROWID

It is permissible for customers to implement their own client-side caching mechanism, and

Oracle provides an interface to use in doing so.

Oracle JDBC Implementation for Result Set Scrollability

Because the underlying server does not support scrollable cursors, Oracle JDBC must

implement scrollability in a separate layer.

It is important to be aware that this is accomplished by using a client-side memory cache to

store rows of a scrollable result set.

Note:

Because all rows of any scrollable result set are stored in the client-side cache, a

situation, where the result set contains many rows, many columns, or very large

columns, might cause the client-side Java Virtual Machine (JVM) to fail. Do not

specify scrollability for a large result set.

17-1

Oracle JDBC Implementation for Result Set Updatability

To support updatability, Oracle JDBC uses

ROWID

to uniquely identify database rows

that appear in a result set. For every query into an updatable result set, Oracle JDBC

driver automatically retrieves the

ROWID

along with the columns you select.

Note:

Client-side caching is not required by updatability in and of itself. In

particular, a forward-only updatable result set will not require a client-side

cache.

17.2 Resultset Limitations and Downgrade Rules

Some types of result sets are not feasible for certain kinds of queries. If you specify an

unfeasible result set type or concurrency type for the query you run, then the JDBC

driver follows a set of rules to determine the best feasible types to use instead.

The actual result set type and concurrency type are determined when the statement is

run, with the driver issuing a

SQLWarning

on the statement object if the desired result

set type or concurrency type is not feasible. The

SQLWarning

object will contain the

reason why the requested type was not feasible. Check for warnings to verify whether

you received the type of result set that you requested.

Result Set Limitations

The following limitations are placed on queries for enhanced result sets. Failure to

follow these guidelines results in the JDBC driver choosing an alternative result set

type or concurrency type.

To produce an updatable result set:

• A query can select from only a single table and cannot contain any join operations.

In addition, for inserts to be feasible, the query must select all non-nullable

columns and all columns that do not have a default value.

• A query cannot use

SELECT *

However, there is a workaround for this.

• A query must select table columns only.

It cannot select derived columns or aggregates, such as the

SUM

MAX

of a set of

columns.

To produce a scroll-sensitive result set:

• A query cannot use

SELECT *

However, there is a workaround for this.

• A query can select from only a single table.

Scrollable and updatable result sets cannot have any column as

Stream

. When the

server has to fetch a

Stream

column, it reduces the fetch size to one and blocks all

Chapter 17

Resultset Limitations and Downgrade Rules

17-2

columns following the

Stream

column until the

Stream

column is read. As a result, columns

cannot be fetched in bulk and scrolled through.

Workaround

As a workaround for the

SELECT *

limitation, you can use table aliases, as shown in the

following example:

SELECT t.* FROM TABLE t ...

Note:

There is a simple way to determine if your query will probably produce a scroll-

sensitive or updatable result set: If you can legally add a

ROWID

column to the query

list, then the query is probably suitable for either a scroll-sensitive or an updatable

result set.

Result Set Downgrade Rules

If the specified result set type or concurrency type is not feasible, then Oracle JDBC driver

uses the following rules in choosing alternate types:

• If the specified result set type is

TYPE_SCROLL_SENSITIVE

, but the JDBC driver cannot

fulfill that request, then the driver attempts a downgrade to

TYPE_SCROLL_INSENSITIVE

• If the specified or downgraded result set type is

TYPE_SCROLL_INSENSITIVE

, but the JDBC

driver cannot fulfill that request, then the driver attempts a downgrade to

TYPE_FORWARD_ONLY

• If the specified concurrency type is

CONCUR_UPDATABLE

, but the JDBC driver cannot fulfill

that request, then the JDBC driver attempts a downgrade to

CONCUR_READ_ONLY

Note:

Any manipulations of the result set type and concurrency type by the JDBC driver

are independent of each other.

Verifying Result Set Type and Concurrency Type

After a query has been run, you can verify the result set type and concurrency type that the

JDBC driver actually used, by calling methods on the result set object.

•

int getType() throws SQLException

This method returns an

int

value for the result set type used for the query.

ResultSet.TYPE_FORWARD_ONLY

ResultSet.TYPE_SCROLL_SENSITIVE

, or

ResultSet.TYPE_SCROLL_INSENSITIVE

are the possible values.

•

int getConcurrency() throws SQLException

This method returns an

int

value for the concurrency type used for the query.

ResultSet.CONCUR_READ_ONLY

ResultSet.CONCUR_UPDATABLE

are the possible values.

Chapter 17

Resultset Limitations and Downgrade Rules

17-3

17.3 About Avoiding Update Conflicts

It is important to be aware of the following facts regarding updatable result sets with

the JDBC drivers:

• The drivers do not enforce write locks for an updatable result set.

• The drivers do not check for conflicts with a result set

DELETE

UPDATE

operation.

A conflict will occur if you try to perform a

DELETE

UPDATE

operation on a row

updated by another committed transaction.

Oracle JDBC drivers use the

ROWID

to uniquely identify a row in a database table. As

long as the

ROWID

is valid when a driver tries to send an

UPDATE

DELETE

operation to

the database, the operation will be run.

The driver will not report any changes made by another committed transaction. Any

conflicts are silently ignored and your changes will overwrite the previous changes.

To avoid such conflicts, use the Oracle

FOR UPDATE

feature when running the query

that produces the result set. This will avoid conflicts, but will also prevent simultaneous

access to the data. Only a single write lock can be held concurrently on a data item.

17.4 Row Fetch Size

By default, when Oracle JDBC runs a query, it retrieves a result set of 10 rows at a

time from the database cursor. This is the default Oracle row fetch size value. You can

change the number of rows retrieved with each trip to the database cursor by changing

the row fetch size value.

Standard JDBC also enables you to specify the number of rows fetched with each

database round-trip for a query, and this number is referred to as the fetch size. In

Oracle JDBC, the row-prefetch value is used as the default fetch size in a statement

object. Setting the fetch size overrides the row-prefetch setting and affects subsequent

queries run through that statement object.

Fetch size is also used in a result set. When the statement object run a query, the

fetch size of the statement object is passed to the result set object produced by the

query. However, you can also set the fetch size in the result set object to override the

statement fetch size that was passed to it.

Note:

Changes made to the fetch size of a statement object after a result set is

produced will have no affect on that result set.

The result set fetch size, either set explicitly, or by default equal to the statement fetch

size that was passed to it, determines the number of rows that are retrieved in any

subsequent trips to the database for that result set. This includes any trips that are still

required to complete the original query, as well as any refetching of data into the result

set. Data can be refetched, either explicitly or implicitly, to update a scroll-sensitive or

scroll-insensitive/updatable result set.

Chapter 17

About Avoiding Update Conflicts

17-4

17.4.1 Setting the Fetch Size

The following methods are available in all

Statement

PreparedStatement

CallableStatement

, and

ResultSet

objects for setting and getting the fetch size:

•

void setFetchSize(int rows) throws SQLException

•

int getFetchSize() throws SQLException

To set the fetch size for a query, call

setFetchSize

on the statement object prior to running

the query. If you set the fetch size to N, then N rows are fetched with each trip to the

database.

After you have run the query, you can call

setFetchSize

on the result set object to override

the statement object fetch size that was passed to it. This will affect any subsequent trips to

the database to get more rows for the original query, as well as affecting any later refetching

of rows.

17.4.2 Presetting the Fetch Direction

The standard JDBC enables to pre-specify the direction, known as the fetch direction, for use

in processing a result set. This allows the JDBC driver to optimize its processing. The

following result set methods are specified:

•

void setFetchDirection(int direction) throws SQLException

•

int getFetchDirection() throws SQLException

Oracle JDBC drivers support only the forward preset value, which you can specify by entering

the

ResultSet.FETCH_FORWARD

static constant value.

The values

ResultSet.FETCH_REVERSE

and

ResultSet.FETCH_UNKNOWN

are not supported.

Attempting to specify them causes a SQL warning, and the settings are ignored.

17.5 About Refetching Rows

The result set

refreshRow

method is supported for some types of result sets for refetching

data. This consists of going back to the database to re-obtain the database rows that

correspond to n rows in the result set, starting with the current row, where n is the fetch size.

This lets you see the latest updates to the database that were made outside of your result

set, subject to the isolation level of the enclosing transaction.

Because refetching re-obtains only rows that correspond to rows already in your result set, it

does nothing about rows that have been inserted or deleted in the database since the original

query. It ignores rows that have been inserted, and rows will remain in your result set even

after the corresponding rows have been deleted from the database. When there is an attempt

to refetch a row that has been deleted in the database, the corresponding row in the result

set will maintain its original values.

Chapter 17

About Refetching Rows

17-5

Note:

If you declare a

TYPE_SCROLL_SENSITIVE

Result Set based on a query with

certain criteria and then externally update the row so that the column values

no longer match the query criteria, the driver behaves as if the row has been

deleted from the database and the row is not retrieved by the query issued.

So, you do not see the updates to the particular row when you call the

refreshRow

method.

Following is the signature of the

refreshRow

method:

void refreshRow() throws SQLException

You must be at a valid current row when you call this method, not outside the row

bounds and not at the insert-row.

The

refreshRow

method is supported for the following result set categories:

• scroll-sensitive/read-only

• scroll-sensitive/updatable

• scroll-insensitive/updatable

Note:

Scroll-sensitive result set functionality is implemented through implicit calls to

refreshRow

17.6 About Viewing Database Changes Made Internally and

Externally

This section discusses the ability of a result set to view the following:

• Own changes of the result set, referred to as internal changes

• Changes made from elsewhere, either from your own transaction outside the

result set, or from other committed transactions, referred to as external changes

Note:

External changes are referred to as other's changes in the standard JDBC

specification.

This section covers the following topics:

• Visibility versus Detection of External Changes

• Summary of Visibility of Internal and External Changes

Chapter 17

About Viewing Database Changes Made Internally and Externally

17-6

• Oracle Implementation of Scroll-Sensitive Result Sets

17.6.1 Visibility versus Detection of External Changes

Regarding the changes made to an underlying database by external sources, there are two

similar but distinct concepts with respect to visibility of the changes from your local result set:

• Visibility of changes

• Detection of changes

A "visible" change means that when you look at a row in the result set, you can see new data

values from changes made by external sources, to the corresponding row in the database.

A "detected" change, however, means that the result set is aware that this is a new value

since the result set was first populated.

Even when an Oracle result set sees new data, as with an external

UPDATE

in a scroll-

sensitive result set, it has no awareness that this data has changed since the result set was

populated. Such changes are not detected.

17.6.2 Summary of Visibility of Internal and External Changes

Table 17-1 summarizes how a result set object in the Oracle JDBC implementation can see

changes made internally through the result set itself, and changes made externally to the

underlying database from elsewhere in your transaction or from other committed

transactions.

Table 17-1 Visibility of Internal and External Changes for Oracle JDBC

Result Set Type Can See

Internal

DELETE?

Can See

Internal

UPDATE?

Can See

Internal

INSERT?

Can See

External

DELETE?

Can See

External

UPDATE?

Can See

External

INSERT?

forward-only no yes no no no no

scroll-sensitive yes yes no no yes no

scroll-insensitive yes yes no no no no

Note:

• Remember that explicit use of the

refreshRow

method, is distinct from the

concept of visibility of external changes.

• Remember that even when external changes are visible, as with

UPDATE

operations underlying a scroll-sensitive result set, they are not detected. The

result set

rowDeleted

rowUpdated

, and

rowInserted

methods always return

false

Chapter 17

About Viewing Database Changes Made Internally and Externally

17-7

17.6.3 Oracle Implementation of Scroll-Sensitive Result Sets

The Oracle implementation of scroll-sensitive result sets involves the concept of a

window, with a window size that is based on the fetch size. The window size affects

how often rows are updated in the result set.

Once you establish a current row by moving to a specified row, the window consists of

the n rows in the result set starting with that row, where n is the fetch size being used

by the result set. Note that there is no current row, and therefore no window, when a

result set is first created. The default position is before the first row, which is not a valid

current row.

As you move from row to row, the window remains unchanged as long as the current

row stays within that window. However, once you move to a new current row outside

the window, you redefine the window to be the N rows starting with the new current

row.

Whenever the window is redefined, the N rows in the database corresponding to the

rows in the new window are automatically refetched through an implicit call to the

refreshRow

method, thereby updating the data throughout the new window.

So external updates are not instantaneously visible in a scroll-sensitive result set.

They are only visible after the automatic refetches just described.

Note:

This kind of refetching is not a highly efficient or optimized methodology and

it has significant performance concerns. Consider carefully before using

scroll-sensitive result sets as currently implemented. There is also a

significant trade-off between sensitivity and performance. The most sensitive

result set is one with a fetch size of 1, which would result in the new current

row being refetched every time you move between rows. However, this

would have a significant impact on the performance of your application.

Chapter 17

About Viewing Database Changes Made Internally and Externally

17-8

JDBC RowSets

This chapter contains the following sections:

• Overview of JDBC RowSets

• About CachedRowSet

• About JdbcRowSet

• About WebRowSet

• About FilteredRowSet

• About JoinRowSet

18.1 Overview of JDBC RowSets

A RowSet is an object that encapsulates a set of rows from either java Database Connectivity

(JDBC) result sets or tabular data sources. RowSets support component-based development

models like JavaBeans, with a standard set of properties and an event notification

mechanism.

RowSets were introduced in JDBC 2.0 through the optional packages. However, the

implementation of RowSets was standardized in the JDBC RowSet Implementations

Specification (JSR-114), which is available as non-optional package since Java Platform,

Standard Edition (Java SE) 5.0. Java SE 6.0 RowSets contain more APIs supporting features

like RowId, National Language Charactersets, and so on. The Java SE Javadocs provide

information about the standard interfaces and base classes for JDBC RowSet

implementations.

The JSR-114 specification includes implementation details for five types of RowSet:

•

CachedRowSet

•

JdbcRowSet

•

WebRowSet

•

FilteredRowSet

•

JoinRowSet

Oracle JDBC supports all five types of RowSets through the interfaces and classes present in

the

oracle.jdbc.rowset

package. Since Oracle Database 11g Release 1, RowSets support

has been added in the server-side drivers. Therefore, starting from Oracle Database 11g

Release 1, RowSets support is uniform across all Oracle JDBC driver types. The standard

Oracle JDBC Java Archive (JAR) files, for example,

ojdbc6.jar

and

ojdbc7.jar

contain the

oracle.jdbc.rowset

package.

18-1

Note:

• The other JAR files with different file suffix names, for example,

ojdbc6_g.jar

ojdbc6dms.jar

, and so on also contain the

oracle.jdbc.rowset

package.

• In Oracle Database 10g release 2, the implementation classes were

packaged in the

ojdbc14.jar

file.

• Prior to Oracle Database 10g release 2, the implementation classes

were packaged in the

ocrs12.jar

file.

• Prior to Oracle Database 11g Release 1, RowSets support was not

available in the server-side drivers.

Note:

In Oracle Database 10g release 2 (10.2), this package is included in the

standard Oracle JDBC JAR files:

classes12.jar

ojdbc5.jar

, and

ojdbc6.jar

. Prior to Oracle Database 10g release 2 (10.2), the row set

implementation classes were packaged in the

ocrs12.jar

file.

To use the Oracle RowSet implementations, you need to import either the entire

oracle.jdbc.rowset

package or specific classes and interfaces from the package for

the required RowSet type. For client-side usage, you also need to include the standard

Oracle JAR files like

ojdbc6.jar

ojdbc7.jar

in the

CLASSPATH

environment

variable.

This section covers the following topics:

• RowSet Properties

• Events and Event Listeners

• Command Parameters and Command Execution

• About Traversing RowSets

18.1.1 RowSet Properties

The

javax.sql.RowSet

interface provides a set of JavaBeans properties that can be

altered to access the data in the data source through a single interface. Example of

properties are connection string, user name, password, type of connection, and the

query string.

See Also:

The Java 2 Platform, Standard Edition (J2SE) Javadoc for a complete list of

properties and property descriptions at

http://docs.oracle.com/javase/

1.5.0/docs/api/javax/sql/RowSet.html

Chapter 18

Overview of JDBC RowSets

18-2

The interface provides standard accessor methods for setting and retrieving the property

values. The following code illustrates setting some of the

RowSet

properties:

...

rowset.setUrl("jdbc:oracle:oci:@");

rowset.setUsername("HR");

rowset.setPassword("hr");

rowset.setCommand("SELECT employee_id, first_name, last_name, salary FROM employees");

...

In this example, the URL, user name, password, and SQL query are set as the

RowSet

properties to retrieve the employee number, employee name, and salary of all the employees

into the

RowSet

object.

18.1.2 Events and Event Listeners

RowSets support JavaBeans events. The following types of events are supported by the

RowSet

interface:

•

cursorMoved

This event is generated whenever there is a cursor movement. For example, when the

method is called.

•

rowChanged

This event is generated when a row is inserted, updated, or deleted from the RowSet.

•

rowSetChanged

This event is generated when the whole RowSet is created or changed. For example,

when the

execute

method is called.

An application component can implement a RowSet listener to listen to these RowSet events

and perform desired operations when the event occurs. Application components, which are

interested in these events, must implement the standard

javax.sql.RowSetListener

interface and register such listener objects with a

RowSet

object. A listener can be registered

using the

RowSet.addRowSetListener

method and unregistered using the

RowSet.removeRowSetListener

method. Multiple listeners can be registered with the same

RowSet

object.

The following code illustrates the registration of a RowSet listener:

...

MyRowSetListener rowsetListener = new MyRowSetListener ();

// adding a rowset listener

rowset.addRowSetListener (rowsetListener);

...

The following code illustrates a listener implementation:

public class MyRowSetListener implements RowSetListener

{

public void cursorMoved(RowSetEvent event)

{

// action on cursor movement

}

public void rowChanged(RowSetEvent event)

{

// action on change of row

Chapter 18

Overview of JDBC RowSets

18-3

}

public void rowSetChanged(RowSetEvent event)

{

// action on changing of rowset

}

}// end of class MyRowSetListener

Applications that need to handle only selected events can implement only the required

event handling methods by using the

oracle.jdbc.rowset.OracleRowSetListenerAdapter

class, which is an abstract class

with empty implementation for all the event handling methods. In the following code,

only the

rowSetChanged

event is handled, while the remaining events are not handled

by the application:

...

rowset.addRowSetListener(new oracle.jdbc.rowset.OracleRowSetListenerAdapter ()

{

public void rowSetChanged(RowSetEvent event)

{

// your action for rowSetChanged

}

);

...

18.1.3 Command Parameters and Command Execution

The

command

property of a

RowSet

object typically represents a SQL query string, which

when processed would populate the

RowSet

object with actual data. Like in regular

JDBC processing, this query string can take input or bind parameters. The

javax.sql.RowSet

interface also provides methods for setting input parameters to this

SQL query. After the required input parameters are set, the SQL query can be

processed to populate the

RowSet

object with data from the underlying data source.

The following code illustrates this simple sequence:

...

rowset.setCommand("SELECT first_name, last_name, salary FROM employees WHERE

employee_id = ?");

// setting the employee number input parameter for employee named "Douglas"

rowset.setInt(1, 199);

rowset.execute();

...

In the preceding example, the employee number 199 is set as the input or bind

parameter for the SQL query specified in the

command

property of the

RowSet

object.

When the SQL query is processed, the

RowSet

object is filled with the employee name

and salary information of the employee whose employee number is 199.

18.1.4 About Traversing RowSets

The

javax.sql.RowSet

interface extends the

java.sql.ResultSet

interface. The

RowSet

interface, therefore, provides cursor movement and positioning methods, which

are inherited from the

ResultSet

interface, for traversing through data in a

RowSet

object. Some of the inherited methods are

absolute

beforeFirst

afterLast

and

Chapter 18

Overview of JDBC RowSets

18-4

The

RowSet

interface can be used just like a

ResultSet

interface for retrieving and updating

data. The

RowSet

interface provides an optional way to implement a scrollable and updatable

result set. All the fields and methods provided by the

ResultSet

interface are implemented in

RowSet

Note:

The Oracle implementation of

ResultSet

provides the scrollable and updatable

properties of the

java.sql.ResultSet

interface.

The following code illustrates how to scroll through a RowSet:

/**

* Scrolling forward, and printing the empno in

* the order in which it was fetched.

...

rowset.setCommand("SELECT empno, ename, sal FROM emp");

rowset.execute();

...

// going to the first row of the rowset

rowset.beforeFirst ();

while (rowset.next ())

System.out.println ("empno: " +rowset.getInt (1));

In the preceding code, the cursor position is initialized to the position before the first row of

the RowSet by the

beforeFirst

method. The rows are retrieved in forward direction using the

method.

The following code illustrates how to scroll through a RowSet in the reverse direction:

/**

* Scrolling backward, and printing the empno in

* the reverse order as it was fetched.

//going to the last row of the rowset

rowset.afterLast ();

while (rowset.previous ())

System.out.println ("empno: " +rowset.getInt (1));

In the preceding code, the cursor position is initialized to the position after the last row of the

RowSet

. The rows are retrieved in reverse direction using the

method of

RowSet

Inserting, updating, and deleting rows are supported by the Row Set feature as they are in

the Result Set feature. In order to make the Row Set updatable, you must call the

setReadOnly(false)

and

acceptChanges

methods.

The following code illustrates the insertion of a row at the fifth position of a Row Set:

...

/**

* Make rowset updatable

rowset.setReadOnly (false);

/**

* Inserting a row in the 5th position of the rowset.

Chapter 18

Overview of JDBC RowSets

18-5

// moving the cursor to the 5th position in the rowset

if (rowset.absolute(5))

{

rowset.moveToInsertRow ();

rowset.updateInt (1, 193);

rowset.updateString (2, "Smith");

rowset.updateInt (3, 7200);

// inserting a row in the rowset

rowset.insertRow ();

// Synchronizing the data in RowSet with that in the database.

rowset.acceptChanges ();

}

...

In the preceding code, a call to the

absolute

method with a parameter

takes the

cursor to the fifth position of the RowSet and a call to the

moveToInsertRow

method

creates a place for the insertion of a new row into the RowSet. The

updateXXX

methods are used to update the newly created row. When all the columns of the row

are updated, the

insertRow

is called to update the RowSet. The changes are

committed through

acceptChanges

method.

18.2 About CachedRowSet

A CachedRowSet is a RowSet in which the rows are cached and the RowSet is

disconnected, that is, it does not maintain an active connection to the database. The

oracle.jdbc.rowset.OracleCachedRowSet

class is the Oracle implementation of

CachedRowSet. It can interoperate with the standard reference implementation. The

OracleCachedRowSet

class in the

ojdbc6.jar

and

ojdbc7.jar

files implements the

standard JSR-114 interface

javax.sql.rowset.CachedRowSet

In the following code, an

OracleCachedRowSet

object is created and the connection

URL, user name, password, and the SQL query for the

RowSet

object is set as

properties. The

RowSet

object is populated using the

execute

method. After the

execute

method has been processed, the

RowSet

object can be used as a

java.sql.ResultSet

object to retrieve, scroll, insert, delete, or update data.

...

RowSet rowset = new OracleCachedRowSet();

rowset.setUrl("jdbc:oracle:oci:@");

rowset.setUsername("HR");

rowset.setPassword("hr");

rowset.setCommand("SELECT employee_id, first_name, last_name, salary FROM

employees");

rowset.execute();

while (rowset.next ())

{

System.out.println("employee_id: " +rowset.getInt (1));

System.out.println("first_name: " +rowset.getString (2));

System.out.println("last_name: " +rowset.getString (3));

System.out.println("sal: " +rowset.getInt (4));

}

...

To populate a

CachedRowSet

object with a query, complete the following steps:

1. Instantiate

OracleCachedRowSet

Chapter 18

About CachedRowSet

18-6

2. Set the

Url

, which is the connection URL,

Username

Password

, and

Command

, which is the

query string, properties for the

RowSet

object. You can also set the connection type, but it

is optional.

3. Call the

execute

method to populate the

CachedRowSet

object. Calling

execute

runs the

query set as a property on this RowSet.

OracleCachedRowSet rowset = new OracleCachedRowSet ();

rowset.setUrl ("jdbc:oracle:oci:@");

rowset.setUsername ("HR");

rowset.setPassword ("hr");

rowset.setCommand ("SELECT employee_id, first_name, last_name, salary FROM

employees");

rowset.execute ();

CachedRowSet

object can be populated with an existing

ResultSet

object, using the

populate

method. To do so, complete the following steps:

1. Instantiate

OracleCachedRowSet

2. Pass the already available

ResultSet

object to the

populate

method to populate the

RowSet

object.

// Executing a query to get the ResultSet object.

ResultSet rset = pstmt.executeQuery ();

OracleCachedRowSet rowset = new OracleCachedRowSet ();

// the obtained ResultSet object is passed to the populate method

// to populate the data in the rowset object.

rowset.populate (rset);

In the preceding example, a

ResultSet

object is obtained by running a query and the

retrieved

ResultSet

object is passed to the

populate

method of the

CachedRowSet

object to

populate the contents of the result set into the CachedRowSet.

Note:

Connection properties, like transaction isolation or the concurrency mode of the

result set, and the bind properties cannot be set in the case where a pre-existent

ResultSet

object is used to populate the

CachedRowSet

object, because the

connection or result set on which the property applies would have already been

created.

The following code illustrates how an

OracleCachedRowSet

object is serialized to a file and

then retrieved:

// writing the serialized OracleCachedRowSet object

{

FileOutputStream fileOutputStream = new FileOutputStream("emp_tab.dmp");

ObjectOutputStream ostream = new ObjectOutputStream(fileOutputStream);

ostream.writeObject(rowset);

ostream.close();

fileOutputStream.close();

}

Chapter 18

About CachedRowSet

18-7

// reading the serialized OracleCachedRowSet object

{

FileInputStream fileInputStream = new FileInputStream("emp_tab.dmp");

ObjectInputStream istream = new ObjectInputStream(fileInputStream);

RowSet rowset1 = (RowSet) istream.readObject();

istream.close();

fileInputStream.close();

}

In the preceding code, a

FileOutputStream

object is opened for an

emp_tab.dmp

file,

and the populated

OracleCachedRowSet

object is written to the file using

ObjectOutputStream

. The serialized

OracleCachedRowSet

object is retrieved using the

FileInputStream

and

ObjectInputStream

objects.

OracleCachedRowSet

takes care of the serialization of non-serializable form of data like

InputStream

OutputStream

, binary large objects (BLOBs), and character large objects

(CLOBs).

OracleCachedRowSets

also implements metadata of its own, which could be

obtained without any extra server round-trip. The following code illustrates how you

can obtain metadata for the RowSet:

...

ResultSetMetaData metaData = rowset.getMetaData();

int maxCol = metaData.getColumnCount();

for (int i = 1; i <= maxCol; ++i)

System.out.println("Column (" + i +") " + metaData.getColumnName(i));

...

Because the

OracleCachedRowSet

class is serializable, it can be passed across a

network or between Java Virtual Machines (JVMs), as done in Remote Method

Invocation (RMI). Once the

OracleCachedRowSet

class is populated, it can move

around any JVM, or any environment that does not have JDBC drivers. Committing the

data in the RowSet requires the presence of JDBC drivers.

The complete process of retrieving the data and populating it in the

OracleCachedRowSet

class is performed on the server and the populated RowSet is

passed on to the client using suitable architectures like RMI or Enterprise Java Beans

(EJB). The client would be able to perform all the operations like retrieving, scrolling,

inserting, updating, and deleting on the RowSet without any connection to the

database. Whenever data is committed to the database, the

acceptChanges

method is

called, which synchronizes the data in the RowSet to that in the database. This

method makes use of JDBC drivers, which require the JVM environment to contain

JDBC implementation. This architecture would be suitable for systems involving a Thin

client like a Personal Digital Assistant (PDA).

After populating the

CachedRowSet

object, it can be used as a

ResultSet

object or any

other object, which can be passed over the network using RMI or any other suitable

architecture.

Some of the other key-features of CachedRowSet are the following:

• Cloning a RowSet

• Creating a copy of a RowSet

• Creating a shared copy of a RowSet

Chapter 18

About CachedRowSet

18-8

CachedRowSet Constraints

All the constraints that apply to an updatable result set are applicable here, except

serialization, because

OracleCachedRowSet

is serializable. The SQL query has the following

constraints:

• References only a single table in the database

• Contains no join operations

• Selects the primary key of the table it references

In addition, a SQL query should also satisfy the following conditions, if new rows are to be

inserted:

• Selects all non-nullable columns in the underlying table

• Selects all columns that do not have a default value

Note:

The

CachedRowSet

cannot hold a large quantity of data, because all the data is

cached in memory. Oracle, therefore, recommends against using

OracleCachedRowSet

with queries that could potentially return a large volume of

data.

Connection properties like, transaction isolation and concurrency mode of the result set,

cannot be set after populating the RowSet, because the properties cannot be applied to the

connection after retrieving the data from the same.

18.3 About JdbcRowSet

A JdbcRowSet is a RowSet that wraps around a

ResultSet

object. It is a connected RowSet

that provides JDBC interfaces in the form of a JavaBean interface. The Oracle

implementation of JdbcRowSet is

oracle.jdbc.rowset.OracleJDBCRowSet

. The

OracleJDBCRowSet

class in

ojdbc6.jar

and

ojdbc7.jar

implements the standard JSR-114

interface

javax.sql.rowset.JdbcRowSet

Table 18-1 shows how the

JdbcRowSet

interface differs from

CachedRowSet

interface.

Table 18-1 The JDBC and Cached Row Sets Compared

RowSet Type Serializable Connected

to Database

Movable

Across

JVMs

Synchronization of

data to database

Presence

of JDBC

Drivers

JDBC Yes Yes No No Yes

Cached Yes No Yes Yes No

JdbcRowSet is a connected RowSet, which has a live connection to the database and all the

calls on the JdbcRowSet are percolated to the mapping call in the JDBC connection,

statement, or result set. A CachedRowSet does not have any connection to the database

open.

Chapter 18

About JdbcRowSet

18-9

JdbcRowSet requires the presence of JDBC drivers unlike a CachedRowSet, which

does not require JDBC drivers during manipulation. However, both JdbcRowSet and

CachedRowSet require JDBC drivers during population of the RowSet and while

committing the changes of the RowSet.

The following code illustrates how a JdbcRowSet is used:

...

RowSet rowset = new OracleJDBCRowSet();

rowset.setUrl("java:oracle:oci:@");

rowset.setUsername("HR");

rowset.setPassword("hr");

rowset.setCommand("SELECT empno, ename, sal FROM emp");

rowset.execute();

while (rowset.next())

{

System.out.println("empno: " + rowset.getInt(1));

System.out.println("ename: " + rowset.getString(2));

System.out.println("sal: " + rowset.getInt(3));

}

...

In the preceding example, the connection URL, user name, password, and SQL query

are set as properties of the

RowSet

object, the SQL query is processed using the

execute

method, and the rows are retrieved and printed by traversing through the data

populated in the

RowSet

object.

18.4 About WebRowSet

A WebRowSet is an extension to CachedRowSet. It represents a set of fetched rows

or tabular data that can be passed between tiers and components in a way such that

no active connections with the data source need to be maintained. The

WebRowSet

interface provides support for the production and consumption of result sets and their

synchronization with the data source, both in Extensible Markup Language (XML)

format and in disconnected fashion. This allows result sets to be shipped across tiers

and over Internet protocols.

The Oracle implementation of WebRowSet is

oracle.jdbc.rowset.OracleWebRowSet

This class, which is in the

ojdbc6.jar

and

ojdbc7.jar

files, implements the standard

JSR-114 interface

javax.sql.rowset.WebRowSet

. This class also extends the

oracle.jdbc.rowset.OracleCachedRowSet

class. Besides the methods available in

OracleCachedRowSet

, the

OracleWebRowSet

class provides the following methods:

•

public OracleWebRowSet() throws SQLException

This is the constructor for creating an

OracleWebRowSet

object, which is initialized

with the default values for an

OracleCachedRowSet

object, a default

OracleWebRowSetXmlReader

, and a default

OracleWebRowSetXmlWriter

•

public void writeXml(java.io.Writer writer) throws SQLException

public void writeXml(java.io.OutputStream ostream) throws SQLException

These methods write the

OracleWebRowSet

object to the supplied

Writer

OutputStream

object in the XML format that conforms to the JSR-114 XML

schema. In addition to the RowSet data, the properties and metadata of the

RowSet are written.

Chapter 18

About WebRowSet

18-10

•

public void writeXml(ResultSet rset, java.io.Writer writer) throws SQLException

public void writeXml(ResultSet rset, java.io.OutputStream ostream) throws

SQLException

These methods create an

OracleWebRowSet

object, populate it with the data in the given

ResultSet

object, and write it to the supplied

Writer

OutputStream

object in the XML

format that conforms to the JSR-114 XML schema.

•

public void readXml(java.io.Reader reader) throws SQLException

public void readXml(java.io.InputStream istream) throws SQLException

These methods read the

OracleWebRowSet

object in the XML format according to its

JSR-114 XML schema, using the supplied

Reader

InsputStream

object.

The Oracle WebRowSet implementation supports Java API for XML Processing (JAXP) 1.2.

Both Simple API for XML (SAX) 2.0 and Document Object Model (DOM) JAXP-conforming

XML parsers are supported. It follows the current JSR-114 W3C XML schema for

WebRowSet.

Applications that use the

readXml(...)

methods should set one of the following two standard

JAXP system properties before calling the methods:

•

javax.xml.parsers.SAXParserFactory

This property is for a SAX parser.

•

javax.xml.parsers.DocumentBuilderFactory

This property is for a DOM parser.

The following code illustrates the use of

OracleWebRowSet

for both writing and reading in XML

format:

import java.sql.*;

import java.io.*;

import oracle.jdbc.rowset.*;

...

String url = "jdbc:oracle:oci8:@";

Connection conn = DriverManager.getConnection(url,"HR","hr");

Statement stmt = conn.createStatement();

ResultSet rset = stmt.executeQuery("select * from employees");

// Create an OracleWebRowSet object and populate it with the ResultSet object

OracleWebRowSet wset = new OracleWebRowSet();

wset.populate(rset);

try

{

// Create a java.io.Writer object

FileWriter out = new FileWriter("xml.out");

// Now generate the XML and write it out

wset.writeXml(out);

}

catch (IOException exc)

{

System.out.println("Couldn't construct a FileWriter");

}

System.out.println("XML output file generated.");

Chapter 18

About WebRowSet

18-11

// Create a new OracleWebRowSet for reading from XML input

OracleWebRowSet wset2 = new OracleWebRowSet();

// Use Oracle JAXP SAX parser

System.setProperty("javax.xml.parsers.SAXParserFactory","oracle.xml.jaxp.JXSAXPar

serFactory");

try

{

// Use the preceding output file as input

FileReader fr = new FileReader("xml.out");

// Now read XML stream from the FileReader

wset2.readXml(fr);

}

catch (IOException exc)

{

System.out.println("Couldn't construct a FileReader");

}

...

Note:

The preceding code uses the Oracle SAX XML parser, which supports

schema validation.

18.5 About FilteredRowSet

A FilteredRowSet is an extension to WebRowSet that provides programmatic support

for filtering its content. This enables you to avoid the overhead of supplying a query

and the processing involved. The Oracle implementation of FilteredRowSet is

oracle.jdbc.rowset.OracleFilteredRowSet

. The

OracleFilteredRowSet

class in the

ojdbc7.jar

files implements the standard JSR-114 interface

javax.sql.rowset.FilteredRowSet

The

OracleFilteredRowSet

class defines the following new methods:

•

public Predicate getFilter();

This method returns a

Predicate

object that defines the filtering criteria active on

the

OracleFilteredRowSet

object.

•

public void setFilter(Predicate p) throws SQLException;

This method takes a

Predicate

object as a parameter. The

Predicate

object

defines the filtering criteria to be applied on the

OracleFilteredRowSet

object. The

methods throws a

SQLException

exception.

Chapter 18

About FilteredRowSet

18-12

Note:

If you are using

classes12.jar

instead of

ojdbc5.jar

and

ojdbc6.jar

for

FilteredRowSet features, then use

OraclePredicate

instead of

Predicate

. The

oracle.jdbc.rowset.OraclePredicate

interface is Oracle specific and is

equivalent to

Predicate

. This interface is used when the JSR-114 packages are not

available.

The predicate set on an

OracleFilteredRowSet

object defines a filtering criteria that is

applied to all the rows in the object to obtain the set of visible rows. The predicate also

defines the criteria for inserting, deleting, and modifying rows. The set filtering criteria acts as

a gating mechanism for all views and updates to the

OracleFilteredRowSet

object. Any

attempt to update the

OracleFilteredRowSet

object, which violates the filtering criteria,

throws a

SQLException

exception.

The filtering criteria set on an

OracleFilteredRowSet

object can be modified by applying a

new

Predicate

object. The new criteria is immediately applied on the object, and all further

views and updates must adhere to this new criteria. A new filtering criteria can be applied

only if there are no reference to the

OracleFilteredRowSet

object.

Rows that fall outside of the filtering criteria set on the object cannot be modified until the

filtering criteria is removed or a new filtering criteria is applied. Also, only the rows that fall

within the bounds of the filtering criteria will be synchronized with the data source, if an

attempt is made to persist the object.

The following code example illustrates the use of OracleFilteredRowSet. Assume a table,

test_table

, with two

NUMBER

columns,

col1

and

col2

. The code retrieves those rows from

the table that have value of

col1

between

and

100

and value of

col2

between

100

and

200

The predicate defining the filtering criteria is as follows:

public class PredicateImpl implements Predicate

{

private int low[];

private int high[];

private int columnIndexes[];

public PredicateImpl(int[] lo, int[] hi, int[] indexes)

{

low = lo;

high = hi;

columnIndexes = indexes;

}

public boolean evaluate(RowSet rs)

{

boolean result = true;

for (int i = 0; i < columnIndexes.length; i++)

{

int columnValue = rs.getInt(columnIndexes[i]);

if (columnValue < low[i] || columnValue > high[i])

result = false;

}

return result;

}

Chapter 18

About FilteredRowSet

18-13

// the other two evaluate(...) methods simply return true

}

The predicate defined in the preceding code is used for filtering content in an

OracleFilteredRowSet

object, as follows:

...

OracleFilteredRowSet ofrs = new OracleFilteredRowSet();

int low[] = {50, 100};

int high[] = {100, 200};

int indexes[] = {1, 2};

ofrs.setCommand("select col1, col2 from test_table");

// set other properties on ofrs like usr/pwd ...

...

ofrs.execute();

ofrs.setPredicate(new PredicateImpl(low, high, indexes));

// this will only get rows with col1 in (50,100) and col2 in (100,200)

while (ofrs.next()) {...}

...

18.6 About JoinRowSet

A JoinRowSet is an extension to WebRowSet that consists of related data from

different RowSets. There is no standard way to establish a SQL

JOIN

between

disconnected RowSets without connecting to the data source. A JoinRowSet

addresses this issue. The Oracle implementation of JoinRowSet is the

oracle.jdbc.rowset.OracleJoinRowSet

class. This class, which is in the

ojdbc7.jar

files, implements the standard JSR-114 interface

javax.sql.rowset.JoinRowSet

Any number of

RowSet

objects, which implement the

Joinable

interface, can be added

to a

JoinRowSet

object, provided they can be related in a SQL

JOIN

. All five types of

RowSet support the

Joinable

interface. The

Joinable

interface provides methods for

specifying the columns based on which the

JOIN

will be performed, that is, the match

columns.

Note:

If you are using

classes12.jar

instead of

ojdbc5.jar

and

ojdbc6.jar

for

JoinRowSet features, then use

OracleJoinable

instead of

Joinable

. The

oracle.jdbc.rowset.OracleJoinable

interface is Oracle-specific and is

equivalent to

Joinable

. This interface is used when the JSR-114 packages

are not available.

A match column can be specified in the following ways:

• Using the

setMatchColumn

method

This method is defined in the

Joinable

interface. It is the only method that can be

used to set the match column before a

RowSet

object is added to a

JoinRowSet

object. This method can also be used to reset the match column at any time.

Chapter 18

About JoinRowSet

18-14

• Using the

addRowSet

method

This is an overloaded method in

JoinRowSet

. Four of the five implementations of this

method take a match column as a parameter. These four methods can be used to set or

reset a match column at the time a

RowSet

object is being added to a

JoinRowSet

object.

In addition to the inherited methods,

OracleJoinRowSet

provides the following methods:

•

public void addRowSet(Joinable joinable) throws SQLException;

public void addRowSet(RowSet rowSet, int i) throws SQLException;

public void addRowSet(RowSet rowSet, String s) throws SQLException;

public void addRowSet(RowSet arowSet[], int an[]) throws SQLException;

public void addRowSet(RowSet arowSet[], String as[]) throws SQLException;

These methods are used to add a

RowSet

object to the

OracleJoinRowSet

object. You

can pass one or more

RowSet

objects to be added to the

OracleJoinRowSet

object. You

can also pass names or indexes of one or more columns, which need to be set as match

column.

•

public Collection getRowSets() throws SQLException;

This method retrieves the

RowSet

objects added to the

OracleJoinRowSet

object. The

method returns a

java.util.Collection

object that contains the

RowSet

objects.

•

public String[] getRowSetNames() throws SQLException;

This method returns a String array containing the names of the

RowSet

objects that are

added to the

OracleJoinRowSet

object.

•

public boolean supportsCrossJoin();

public boolean supportsFullJoin();

public boolean supportsInnerJoin();

public boolean supportsLeftOuterJoin();

public boolean supportsRightOuterJoin();

These methods return a boolean value indicating whether the

OracleJoinRowSet

object

supports the corresponding

JOIN

type.

•

public void setJoinType(int i) throws SQLException;

This method is used to set the

JOIN

type on the

OracleJoinRowSet

object. It takes an

integer constant as defined in the

javax.sql.rowset.JoinRowSet

interface that specifies

the

JOIN

type.

•

public int getJoinType() throws SQLException;

This method returns an integer value that indicates the

JOIN

type set on the

OracleJoinRowSet

object. This method throws a

SQLException

exception.

•

public CachedRowSet toCachedRowSet() throws SQLException;

This method creates a

CachedRowSet

object containing the data in the

OracleJoinRowSet

object.

•

public String getWhereClause() throws SQLException;

This method returns a String containing the SQL-like description of the

WHERE

clause

used in the

OracleJoinRowSet

object. This methods throws a

SQLException

exception.

Chapter 18

About JoinRowSet

18-15

The following code illustrates how

OracleJoinRowSet

is used to perform an inner join

on two RowSets, whose data come from two different tables. The resulting RowSet

contains data as if they were the result of an inner join on these two tables. Assume

that there are two tables, an

Order

table with two

NUMBER

columns

Order_id

and

Person_id

, and a

Person

table with a

NUMBER

column

Person_id

and a

VARCHAR2

column

Name

...

// RowSet holding data from table Order

OracleCachedRowSet ocrsOrder = new OracleCachedRowSet();

...

ocrsOrder.setCommand("select order_id, person_id from order");

...

// Join on person_id column

ocrsOrder.setMatchColumn(2);

ocrsOrder.execute();

// Creating the JoinRowSet

OracleJoinRowSet ojrs = new OracleJoinRowSet();

ojrs.addRowSet(ocrsOrder);

// RowSet holding data from table Person

OracleCachedRowSet ocrsPerson = new OracleCachedRowSet();

...

ocrsPerson.setCommand("select person_id, name from person");

...

// do not set match column on this RowSet using setMatchColumn().

//use addRowSet() to set match column

ocrsPerson.execute();

// Join on person_id column, in another way

ojrs.addRowSet(ocrsPerson, 1);

// now we can go the JoinRowSet as usual

ojrs.beforeFirst();

while (ojrs.next())

System.out.println("order id = " + ojrs.getInt(1) + ", " + "person id = " +

ojrs.getInt(2) + ", " + "person's name = " + ojrs.getString(3));

...

Chapter 18

About JoinRowSet

18-16

Globalization Support

The Oracle Java Database Connectivity (JDBC) drivers provide globalization support,

formerly known as National Language Support (NLS). Globalization support enables you to

retrieve data or insert data into a database in any character set that Oracle supports. If the

clients and the server use different character sets, then the driver provides the support to

perform the conversions between the database character set and the client character set.

This chapter contains the following sections:

• About Providing Globalization Support

• NCHAR_ NVARCHAR2_ NCLOB and the defaultNChar Property

• New Methods for National Character Set Type Data in JDK 6

Note:

• Starting from Oracle Database 10g, the

NLS_LANG

variable is no longer part of

the JDBC globalization mechanism. The JDBC driver does not check NLS

environment. So, setting it has no effect.

• The JDBC server-side internal driver provides complete globalization support

and does not require any globalization extension files.

• JDBC 4.0 includes methods for reading and writing national character set

values. You should use these methods when using JSE 6 or later.

Related Topics

• Oracle Character Data Types Support

• Oracle Database Globalization Support Guide

19.1 About Providing Globalization Support

The basic Java Archive (JAR) file

ojdbc7.jar

, contains all the necessary classes to provide

complete globalization support for:

• Oracle character sets for

CHAR

VARCHAR

LONGVARCHAR

, or

CLOB

data that is not being

retrieved or inserted as a data member of an Oracle object or collection type.

•

CHAR

VARCHAR

data members of object and collection for the character sets

US7ASCII

WE8DEC

WE8ISO8859P1

WE8MSWIN1252

, and

UTF8

To use any other character sets in

CHAR

VARCHAR

data members of objects or collections,

you must include

orai18n.jar

in the

CLASSPATH

environment variable:

ORACLE_HOME/jlib/orai18n.jar

19-1

Note:

Previous releases depended on the

nls_charset12.zip

file. This file is now

obsolete.

Compressing orai18n.jar

The

orai18n.jar

file contains many important character set and globalization support

files. You can reduce the size of

orai18n.jar

using the built-in customization tool, as

follows:

java -jar orai18n.jar -custom-charsets-jar [jar/zip_filename] -charset

characterset_name [characterset_name ...]

For example, if you want to create a custom character set file,

custom_orai18n_ja.jar

, that includes the JA16SJIS and JA16EUC character sets,

then issue the following command:

$ java -jar orai18n.jar -custom-charsets-jar custom_orai18n_ja.jar -charset

JA16SJIS JA16EUC

The output of the command is as follows:

Added Character set : JA16SJIS

Added Character set : JA16EUC

If you do not specify a file name for your custom JAR/ZIP file, then a file with the name

jdbc_orai18n_cs.jar

is created in the current working directory. Also, for your custom

JAR/ZIP file, you cannot specify a name that starts with

orai18n

If any invalid or unsupported character set name is specified in the command, then no

output JAR/ZIP file will be created. If the custom JAR/ZIP file exists, then the file will

not be updated or removed.

The custom character set JAR/ZIP does not accept any command. However, it prints

the version information and the command that was used to generate the JAR/ZIP file.

For example, you have

jdbc_orai18n_cs.zip

, the command that displays the

information and the displayed information is as follows:

$ java -jar jdbc_orai18n_cs.jar

Oracle Globalization Development Kit - 12.1.X.X.X Release

This custom character set jar/zip file was created with the following command:

java -jar orai18n.jar -custom-charsets-jar jdbc_orai18n_cs.jar -charset

WE8ISO8859P15

The limitation to the number of character sets that can be specified depends on that of

the shell or command prompt of the operating system. It is certified that all supported

character sets can be specified with the command.

Chapter 19

About Providing Globalization Support

19-2

Note:

If you are using a custom character set, then you need to perform the following so

that JDBC supports the custom character set:

1. After creating the

.nlt

and

.nlb

files as part of the process of creating a

custom character set, create

.glb

files for the newly created character set and

also for the

lx0boot.nlt

file using the following command:

java -classpath $ORACLE_HOME/jlib/orai18n.jar:$ORACLE_HOME/lib/

xmlparserv2.jar Ginstall -[add | a] <NLT_file_name>

2. Add the generated files and

$ORACLE_HOME/jlib/orai18n-mappings.jar

into

the

classpath

environment variable while executing the JDBC code that

connects to the database with the custom character set.

19.2 NCHAR, NVARCHAR2, NCLOB and the defaultNChar

Property

By default, the

oracle.jdbc.OraclePreparedStatement

interface treats the data type of all

the columns in the same way as they are encoded in the database character set. However,

since Oracle Database 10g, if you set the value of

oracle.jdbc.defaultNChar

system

property to

true

, then JDBC treats all character columns as being national-language.

The default value of

defaultNChar

is false. If the value of

defaultNChar

is false, then you

must call the

setFormOfUse(<column_Index>, OraclePreparedStatement.FORM_NCHAR)

method for those columns that specifically need national-language characters. For example:

PreparedStatement pstmt =

conn.prepareStatement("insert into TEST values(?,?,?)");

pstmt.setFormOfUse(1, OraclePreparedStatement.FORM_NCHAR);

pstmt.setString(1, myUnicodeString1); // NCHAR column

pstmt.setFormOfUse(2, OraclePreparedeStatement.FORM_NCHAR);

pstmt.setString(2, myUnicodeString2); // NVARCHAR2 column

If you want to set the value of

defaultNChar

true

, then specify the following at the

command-line:

java -Doracle.jdbc.defaultNChar=true myApplication

If you prefer, then you can also specify

defaultNChar

as a connection property and access

NCHAR

NVARCHAR2

, or

NCLOB

data.

Properties props = new Properties();

props.put(OracleConnection.CONNECTION_PROPERTY_DEFAULTNCHAR, "true");

// set URL, username, password, and so on.

...

Connection conn = DriverManager.getConnection(props);

If the value of

defaultNChar

true

, then you should call the

setFormOfUse(<column_Index>, FORM_CHAR)

for columns that do not need national-language

characters. For example:

PreparedStatement pstmt =

conn.prepareStatement("insert into TEST values(?,?,?)");

Chapter 19

NCHAR, NVARCHAR2, NCLOB and the defaultNChar Property

19-3

pstmt.setFormOfUse(3, OraclePreparedStatement.FORM_CHAR);

pstmt.setString(3, myString); // CHAR column

Note:

If you set the value of

defaultNChar

true

and then access

CHAR

columns,

then the database will implicitly convert all

CHAR

data into

NCHAR

. This

conversion has a substantial performance impact.

Note:

• Always use

java.lang.String

for character data instead of

oracle.sql.CHAR

CHAR

is provided only for backward compatibility.

• You can also use the

setObject

method to access national character set

types, but if the

setObject

method is used, then the target data type

must be specified as

Types.NCHAR

Types.NCLOB

Types.NVARCHAR

, or

Types.LONGNVARCHAR

Note:

In Oracle Database, SQL strings are converted to the database character

set. Therefore you need to keep in mind the following:

• In Oracle Database 10g release 1 (10.1) and earlier releases, JDBC

drivers do not support any

NCHAR

literal (n'...') containing Unicode

characters that are not representable in the database character set. All

Unicode characters that are not representable in the database character

set get corrupted.

• If an Oracle Database 10g release 2 (10.2) JDBC driver is connected to

an Oracle Database 10g release 2 (10.2) database server, then all

NCHAR

literals (n'...') are converted to Unicode literals (u'...') and all non-ASCII

characters are converted to their corresponding Unicode escape

sequence. This is done automatically to prevent data corruption.

• If an Oracle Database 10g release 2 (10.2) JDBC driver is connected to

an Oracle Database 10g release 1 (10.1) or earlier database server, then

NCHAR

literals (n'...') are not converted and any character that is not

representable in the database character set gets corrupted.

19.3 New Methods for National Character Set Type Data in

JDK 6

JDBC 4.0 introduces support for the following four additional SQL types to access the

national character set types:

Chapter 19

New Methods for National Character Set Type Data in JDK 6

19-4

•

NCHAR

•

NVARCHAR

•

LONGNVARCHAR

•

NCLOB

These types are similar to the

CHAR

VARCHAR

LONGVARCHAR

, and

CLOB

types, except that the

values are encoded using the national character set. The JDBC specification uses the

String

class to represent

NCHAR

NVARCHAR

, and

LONGNVARCHAR

data, and the

NClob

class to represent

NCLOB

values.

To retrieve a national character value, an application calls one of the following methods:

•

getNString

•

getNClob

•

getNCharacterStream

•

getObject

Note:

The

getClob

method may be used to return an

NClob

object since

NClob

implements

Clob

To specify a value for a parameter marker of national character type, an application calls one

of the following methods:

•

setNString

•

setNCharacterStream

•

setNClob

•

setObject

Note:

You can use the

setFormOfUse

method to specify a national character value in JDK

6. But this practice is discouraged because this method will be deprecated in future

release. So, Oracle recommends you to use the methods discussed in this section.

See Also:

If the

setObject

method is used, then the target data type must be specified as

Types.NCHAR

Types.NCLOB

Types.NVARCHAR

, or

Types.LONGNVARCHAR

Chapter 19

New Methods for National Character Set Type Data in JDK 6

19-5

Part V

Performance and Scalability

This part consists of chapters that discuss the Oracle Java Database Connectivity (JDBC)

features that enhance performance, such as Statement caching and Oracle Call Interface

(OCI) connection pooling. It also includes a chapter that provides information about Oracle

performance extensions, such as update batching and row prefetching.

Part V contains the following chapters:

• Statement and Result Set Caching

• Performance Extensions

• JDBC Reactive Extensions

• OCI Connection Pooling

• Database Resident Connection Pooling

• JDBC Support for Database Sharding

• Oracle Advanced Queuing

• Continuous Query Notification

Statement and Result Set Caching

This chapter describes the benefits and use of Statement caching, an Oracle Java Database

Connectivity (JDBC) extension.

Note:

Use statement caching only when you are sure that the table structure remains the

same in the database. If you alter the table structure and then reuse a statement

that was created and executed before changing the table structure, then you may

get an error.

This chapter contains the following sections:

• About Statement Caching

• About Using Statement Caching

• About Reusing Statements Objects

• About Result Set Caching

20.1 About Statement Caching

Statement caching improves performance by caching executable statements that are used

repeatedly, such as in a loop or in a method that is called repeatedly. Starting from JDBC 3.0,

JDBC standards define a statement-caching interface.

Statement caching can do the following:

• Prevent the overhead of repeated cursor creation

• Prevent repeated statement parsing and creation

• Reuse data structures in the client

This section covers the following topics:

• Basics of Statement Caching

• Implicit Statement Caching

• Explicit Statement Caching

20-1

Note:

Oracle strongly recommends you use the implicit Statement cache. Oracle

JDBC drivers are designed on the assumption that the implicit Statement

cache is enabled. So, not using the Statement cache will have a negative

impact on performance.

20.1.1 Basics of Statement Caching

Applications use the Statement cache to cache statements associated with a particular

physical connection. The cache is associated with an

OracleConnection

object.

OracleConnection

includes methods to enable Statement caching. When you enable

Statement caching, a statement object is cached when you call the

method.

Because each physical connection has its own cache, multiple caches can exist if you

enable Statement caching for multiple physical connections. When you enable

Statement caching on a connection cache, the logical connections benefit from the

Statement caching that is enabled on the underlying physical connection. If you try to

enable Statement caching on a logical connection held by a connection cache, then

this will throw an exception.

There are two types of Statement caching: implicit and explicit. Each type of Statement

cache can be enabled or disabled independent of the other. You can have either,

neither, or both in effect. Both types of Statement caching share a single cache per

connection.

20.1.2 Implicit Statement Caching

When you enable implicit Statement caching, JDBC automatically caches the prepared

or callable statement when you call the

method of this statement object. The

prepared and callable statements are cached and retrieved using standard connection

object and statement object methods.

Plain statements are not implicitly cached, because implicit Statement caching uses a

SQL string as a key and plain statements are created without a SQL string. Therefore,

implicit Statement caching applies only to the

OraclePreparedStatement

and

OracleCallableStatement

objects, which are created with a SQL string. You cannot

use implicit Statement caching with

OracleStatement

. When you create an

OraclePreparedStatement

OracleCallableStatement

, the JDBC driver

automatically searches the cache for a matching statement. The match criteria are the

following:

• The SQL string in the statement must be identical to one in the cache.

• The statement type must be the same, that is, prepared or callable.

• The scrollable type of result sets produced by the statement must be the same,

that is, forward-only or scrollable.

If a match is found during the cache search, then the cached statement is returned. If

a match is not found, then a new statement is created and returned. In either case, the

statement, along with its cursor and state are cached when you call the

method

of the statement object.

Chapter 20

About Statement Caching

20-2

When a cached

OraclePreparedStatement

OracleCallableStatement

object is retrieved,

the state and data information are automatically reinitialized and reset to default values, while

metadata is saved. Statements are removed from the cache to conform to the maximum size

using a Least Recently Used (LRU) algorithm.

Note:

The JDBC driver does not clear metadata. However, although metadata is saved for

performance reasons, it has no semantic impact. A statement that comes from the

implicit cache appears as if it were newly created.

You can prevent a particular statement from being implicitly cached.

Related Topics

• About Using Implicit Statement Caching

20.1.3 Explicit Statement Caching

Explicit Statement caching enables you to cache and retrieve selected prepared and callable

statements. Explicit Statement caching relies on a key, an arbitrary Java

String

that you

provide.

Note:

Plain statements cannot be cached.

Because explicit Statement caching retains statement data and state as well as metadata, it

has a performance edge over implicit Statement caching, which retains only metadata.

However, you must be cautious when using this type of caching, because explicit Statement

caching saves all three types of information for reuse and you may not be aware of what data

and state are retained from prior use of the statements.

Implicit and explicit Statement caching can be differentiated on the following points:

• Retrieving statements

In the case of implicit Statement caching, you take no special action to retrieve

statements from a cache. Instead, whenever you call

prepareStatement

prepareCall

JDBC automatically checks the cache for a matching statement and returns it if found.

However, in the case of explicit Statement caching, you use specialized Oracle

WithKey

methods to cache and retrieve statement objects.

• Providing key

Implicit Statement caching uses the SQL string of a prepared or callable statement as the

key, requiring no action on your part. In contrast, explicit Statement caching requires you

to provide a Java

String

, which it uses as the key.

• Returning statements

Chapter 20

About Statement Caching

20-3

During implicit Statement caching, if the JDBC driver cannot find a statement in

cache, then it will automatically create one. However, during explicit Statement

caching, if the JDBC driver cannot find a matching statement in cache, then it will

return a

null

value.

Table 20-1 compares the different methods employed in implicit and explicit Statement

caching.

Table 20-1 Comparing Methods Used in Statement Caching

Type of

Caching

Allocate Insert Into Cache Retrieve From Cache

Implicit

prepareStatement

prepareCall

close prepareStatement prepareCall

Explicit

createStatement

prepareStatement

prepareCall

closeWithKey getStatementWithKey

getCallWithKey

20.2 About Using Statement Caching

This section discusses the following topics:

• About Enabling and Disabling Statement Caching

• About Closing a Cached Statement

• About Using Implicit Statement Caching

• About Using Explicit Statement Caching

20.2.1 About Enabling and Disabling Statement Caching

When using the

OracleConnection

API, implicit and explicit Statement caching can be

enabled or disabled independent of one other. You can have either, neither, or both of

them in effect.

Enabling Implicit Statement Caching

There are two ways to enable implicit Statement caching. The first method enables

Statement caching on a nonpooled physical connection, where you need to explicitly

specify the Statement size for every connection, using the

setStatementCacheSize

method. The second method enables Statement caching on a pooled logical

connection. Each connection in the pool has its own Statement cache with the same

maximum size that can be specified by setting the

MaxStatementsLimit

property.

Method 1

Perform the following steps:

• Call the

OracleDataSource.setImplicitCachingEnabled(true)

method on the

connection to set the

OracleDataSource

property

implicitCachingEnabled

true

. For example:

OracleDataSource ods = new OracleDataSource();

...

Chapter 20

About Using Statement Caching

20-4

ods.setImplicitCachingEnabled(true);

...

• Call the

OracleConnection.setStatementCacheSize

method on the physical connection.

The argument you supply is the maximum number of statements in the cache. For

example, the following code specifies a cache size of ten statements:

((OracleConnection)conn).setStatementCacheSize(10);

Method 2

Perform the following steps:

• Set the

OracleDataSource

properties

implicitCachingEnabled

and

connectionCachingEnabled

true

. For example:

OracleDataSource ods = new OracleDataSource();

...

ods.setConnectionCachingEnabled( true );

ods.setImplicitCachingEnabled( true );

...

• Set the

MaxStatementsLimit

property to a positive integer on the connection cache,

when using the connection cache. For example:

Properties cacheProps = new Properties();

...

cacheProps.put( "MaxStatementsLimit", "50" );

To determine whether implicit caching is enabled, call

getImplicitCachingEnabled

, which

returns

true

if implicit caching is enabled,

false

otherwise.

Note:

Enabling Statement caching enables both implicit and explicit Statement caching.

Disabling Implicit Statement Caching

Disable implicit Statement caching by calling

setImplicitCachingEnabled(false)

on the

connection or by setting the

ImplicitCachingEnabled

property to

false

Enabling Explicit Statement Caching

To enable explicit Statement caching you must first set the Statement cache size. For setting

the cache size, call

OracleConnection.setStatementCacheSize

method on the physical

connection. The argument you supply is the maximum number of statements in the cache. An

argument of

specifies no caching. To check the cache size, use the

getStatementCacheSize

method in the following way:

System.out.println("Stmt Cache size is " +

((OracleConnection)conn).getStatementCacheSize());

The following code specifies a cache size of ten statements:

((OracleConnection)conn).setStatementCacheSize(10);

Enable explicit Statement caching by calling

setExplicitCachingEnabled(true)

on the

connection.

Chapter 20

About Using Statement Caching

20-5

To determine whether explicit caching is enabled, call

getExplicitCachingEnabled

which returns

true

if explicit caching is enabled,

false

otherwise.

Note:

• You enable implicit and explicit caching for a particular physical

connection independently. Therefore, it is possible to do Statement

caching both implicitly and explicitly during the same session.

• Implicit and explicit Statement caching share the same cache.

Remember this when you set the statement cache size.

Disabling Explicit Statement Caching

Disable explicit Statement caching by calling

setExplicitCachingEnabled(false)

Disabling caching or closing the cache purges the cache. The following example

disables explicit Statement caching:

((OracleConnection)conn).setExplicitCachingEnabled(false);

20.2.2 About Closing a Cached Statement

Perform the following to close a Statement and assure that it is not returned to the

cache:

In J2SE 5.0

• Disable caching for that statement

stmt.setDisableStmtCaching(true);

• Call the

method of the statement object

stmt.close();

In JSE 6.0

stmt.setPoolable(false);

stmt.close();

Physically Closing a Cached Statement

With implicit Statement caching enabled, you cannot physically close statements

manually. The

method of a statement object caches the statement instead of

closing it. The statement is physically closed automatically under one of following three

conditions:

• When the associated connection is closed

• When the cache reaches its size limit and the least recently used statement object

is preempted from cache by the LRU algorithm

• If you call the

method on a statement for which Statement caching is

disabled

Chapter 20

About Using Statement Caching

20-6

20.2.3 About Using Implicit Statement Caching

Once you enable implicit Statement caching, by default, all prepared and callable statements

are automatically cached. Implicit Statement caching includes the following steps:

1. Enable implicit Statement caching.

2. Allocate a statement using one of the standard methods.

3. Disable implicit Statement caching for any particular statement you do not want to cache.

This is an optional step.

4. Cache the statement using the

method.

5. Retrieve the implicitly cached statement by calling the appropriate standard prepare

method.

Allocating a Statement for Implicit Caching

To allocate a statement for implicit Statement caching, use either the

prepareStatement

prepareCall

method as you would typically.

The following code allocates a new statement object called

pstmt

PreparedStatement pstmt = conn.prepareStatement

("UPDATE emp SET ename = ? WHERE rowid = ?");

Disabling Implicit Statement Caching for a Particular Statement

With implicit Statement caching enabled for a connection, by default, all callable and

prepared statements of that connection are automatically cached. To prevent a particular

callable or prepared statement from being implicitly cached, use the

setDisableStmtCaching

method of the statement object. You can manage cache space by calling the

setDisableStmtCaching

method on any infrequently used statement.

The following code disables implicit Statement caching for

pstmt

PreparedStatement pstmt = conn.prepareStatement("SELECT 1 from DUAL");

((OraclePreparedStatement)pstmt).setDisableStmtCaching(true);

pstmt.close ();

Note:

If you are using JSE 6, then you can disable Statement caching by using the

standard JDBC 4.0 method

setPoolable

PreparedStatement.setPoolable(false);

Use the following to check whether the

Statement

object is poolable:

Statement.isPoolable();

Implicitly Caching a Statement

To cache an allocated statement, call the

method of the statement object. When you

call the

method on an

OraclePreparedStatement

OracleCallableStatement

object,

Chapter 20

About Using Statement Caching

20-7

the JDBC driver automatically puts this statement in cache, unless you have disabled

caching for this statement.

The following code caches the

pstmt

statement:

pstmt.close ();

Retrieving an Implicitly Cached Statement

To retrieve an implicitly cached statement, call either the

prepareStatement

prepareCall

method, depending on the statement type.

The following code retrieves

pstmt

from cache using the

prepareStatement

method:

pstmt = conn.prepareStatement ("UPDATE emp SET ename = ? WHERE rowid = ?");

20.2.3.1 Methods Used in Statement Allocation and Implicit Statement Caching

Table 20-2 describes the methods used to allocate statements and retrieve implicitly

cached statements.

Table 20-2 Methods Used in Statement Allocation and Implicit Statement

Caching

Method Functionality for Implicit Statement Caching

prepareStatement

Performs a cache search that either finds and returns the

desired cached

OraclePreparedStatement

object or

allocates a new

OraclePreparedStatement

object if a match

is not found

prepareCall

Performs a cache search that either finds and returns the

desired cached

OracleCallableStatement

object or

allocates a new

OracleCallableStatement

object if a match

is not found

Example 20-1 provides a sample code that shows how to enable implicit statement

caching.

Example 20-1 Using Implicit Statement Cache

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.Properties;

import javax.sql.DataSource;

import oracle.jdbc.OracleConnection;

import oracle.jdbc.pool.OracleDataSource;

public class TestJdbc

{

/**

* Get a Connection, prepare a statement, execute a query, fetch the results,

close the connection.

* @param ods the DataSource used to get the connection.

private static void doSQL( DataSource ods ) throws SQLException

{

final String SQL = "select username from all_users";

OracleConnection conn = null;

PreparedStatement ps = null;

Chapter 20

About Using Statement Caching

20-8

ResultSet rs = null;

try

{

conn = (OracleConnection) ods.getConnection();

System.out.println( "Connection:" + conn );

System.out.println( "Connection getImplicitCachingEnabled:" +

conn.getImplicitCachingEnabled() );

System.out.println( "Connection getStatementCacheSize:" +

conn.getStatementCacheSize() );

ps = conn.prepareStatement( SQL );

System.out.println( "PreparedStatement:" + ps );

rs = ps.executeQuery();

while ( rs.next() )

{

String owner = rs.getString( 1 );

System.out.println( owner );

}

finally

{

if ( rs != null )

{

rs.close();

}

if ( ps != null )

{

ps.close();

conn.close();

}

public static void main( String[] args )

{

try

{

OracleDataSource ods = new OracleDataSource();

ods.setDriverType( "thin" );

ods.setServerName( "localhost" );

ods.setPortNumber( 5221 );

ods.setServiceName( "orcl" );

ods.setUser( "HR" );

ods.setPassword( "hr" );

ods.setConnectionCachingEnabled( true );

ods.setImplicitCachingEnabled( true );

Properties cacheProps = new Properties();

cacheProps.put( "InitialLimit", "1" );

cacheProps.put( "MinLimit", "1" );

cacheProps.put( "MaxLimit", "5" );

cacheProps.put( "MaxStatementsLimit", "50" );

ods.setConnectionCacheProperties( cacheProps );

System.out.println( "DataSource getImplicitCachingEnabled: " +

ods.getImplicitCachingEnabled() );

for ( int i = 0; i < 5; i++ )

{

doSQL( ods );

}

catch ( Exception ex )

{

ex.printStackTrace();

}

Chapter 20

About Using Statement Caching

20-9

}

20.2.4 About Using Explicit Statement Caching

A prepared or callable statement can be explicitly cached when you enable explicit

Statement caching. Explicit Statement caching includes the following steps:

1. Enable explicit Statement caching.

2. Allocate a statement using one of the standard methods.

3. Explicitly cache the statement by closing it with a key, using the

closeWithKey

method.

4. Retrieve the explicitly cached statement by calling the appropriate Oracle WithKey

method, specifying the appropriate key.

5. Re-cache an open, explicitly cached statement by closing it again with the

closeWithKey

method. Each time a cached statement is closed, it is re-cached

with its key.

Allocating a Statement for Explicit Caching

To allocate a statement for explicit Statement caching, use either the

createStatement

prepareStatement

, or

prepareCall

method as you would typically.

The following code allocates a new statement object called

pstmt

PreparedStatement pstmt =

conn.prepareStatement ("UPDATE emp SET ename = ? WHERE rowid = ?");

Explicitly Caching a Statement

To explicitly cache an allocated statement, call the

closeWithKey

method of the

statement object, specifying a key. The key is an arbitrary Java

String

that you

provide. The

closeWithKey

method caches a statement as is. This means the data,

state, and metadata are retained and not cleared.

The following code caches the

pstmt

statement with the key

"mykey"

((OraclePreparedStatement)pstmt).closeWithKey ("mykey");

Retrieving an Explicitly Cached Statement

To recall an explicitly cached statement, call either the

getStatementWithKey

getCallWithKey

methods depending on the statement type.

If you retrieve a statement with a specified key, then the JDBC driver searches the

cache for the statement, based on the specified key. If a match is found, then the

matching statement is returned along with its state, data, and metadata. This

information is as it was when the statement was last closed. If a match is not found,

then the JDBC driver returns

null

The following code recalls

pstmt

from cache using the

"mykey"

key with the

getStatementWithKey

method. Recall that the

pstmt

statement object was cached

with the

"mykey"

key.

pstmt = ((OracleConnection)conn).getStatementWithKey ("mykey");

Chapter 20

About Using Statement Caching

20-10

If you call the

creationState

method on the

pstmt

statement object, then the method returns

EXPLICIT

Note:

When you retrieve an explicitly cached statement, ensure that you use the method

that is appropriate for your statement type when specifying the key. For example, if

you used the

prepareStatement

method to allocate a statement, then use the

getStatementWithKey

method to retrieve that statement from cache. The JDBC

driver does not verify the type of statement it is returning.

20.2.4.1 Methods Used to Retrieve Explicitly Cached Statements

Table 20-3 describes the methods used to retrieve explicitly cached statements.

Table 20-3 Methods Used to Retrieve Explicitly Cached Statements

Method Functionality for Explicit Statement Caching

getStatementWithKey

Specifies the key needed to retrieve a prepared

statement from cache

getCallWithKey

Specifies the key needed to retrieve a callable statement

from cache

20.3 About Reusing Statements Objects

The JDBC 3.0 specification introduces the feature of statement pooling that enables an

application to reuse a

PreparedStatement

object in the same way as it uses a

Connection

object. The

PreparedStatement

objects can be reused by multiple logical connections in a

transparent manner.

This section covers the following topics:

• About Using a Pooled Statement

• About Closing a Pooled Statement

Note:

The Oracle JDBC Drivers use implicit statement caching to support statement

pooling.

20.3.1 About Using a Pooled Statement

An application can find out whether a data source supports statement pooling by calling the

isPoolable

method from the

Statement

interface. If the return value is

true

, then the

application knows that the

PreparedStatement

object is being pooled. The application can

Chapter 20

About Reusing Statements Objects

20-11

also request a statement to be pooled or not pooled by using the

setPoolable

method

from the

Statement

interface.

Reusing of pooled statement should be completely transparent to the application, that

is, the application code should remain the same whether a

PreparedStatement

object

participates in statement pooling or not. If an application closes a

PreparedStatement

object, it must still call

Connection.prepareStatement

method in order to reuse it.

Note:

An application has no direct control over how statements are pooled. A pool

of statements is associated with a

PooledConnection

object, whose behavior

is determined by the properties of the

ConnectionPoolDataSource

object that

produced it.

20.3.2 About Closing a Pooled Statement

An application closes a pooled statement exactly the same way it closes a nonpooled

statement. Once a statement is closed, whether is it pooled or nonpooled, it is no

longer available for use by the application and an attempt to reuse it causes an

exception to be thrown. The only difference visible is that an application cannot directly

close a physical statement that is being pooled. This is done by the pool manager. The

method

PooledConnection.closeAll

closes all of the statements open on a given

physical connection, which releases the resources associated with those statements.

The following methods can close a pooled statement:

•

This

java.sql.Statement

interface method is called by an application. If the

statement is being pooled, then it closes the logical statement used by the

application but does not close the physical statement being pooled.

•

This

java.sql.Connection

interface method is called by an application. This

method acts differently depending upon whether the connection using the

statement is being pooled or not:

– Nonpooled connection

This method closes the physical connection and all statements created by that

connection. This is necessary because the garbage collection mechanism is

unable to detect when externally managed resources can be released.

– Pooled connection

This method closes the logical connection and the logical statements it

returned, but leaves open the underlying

PooledConnection

object and any

associated pooled statements

•

PooledConnection.closeAll

This method is called by the connection pool manager to close all of the physical

statements being pooled by the

PooledConnection

object

Chapter 20

About Reusing Statements Objects

20-12

20.4 About Result Set Caching

Your applications sometime send repetitive queries to the database. To improve the response

time of repetitive queries, results of queries, query fragments, and PL/SQL functions can be

cached in memory. A result cache stores the results of queries shared across all sessions.

When these queries are executed repeatedly, the results are retrieved directly from the cache

memory.

Note:

If a result set is very large, then it may not be cached due to size restrictions.

You must annotate a query or query fragment with a result cache hint to indicate that results

are to be stored in the query result cache.

The query result set can be cached in the following ways:

• Server-Side Result Set Cache

• Client-Side Result Set Cache

Note:

• The server-side and client result set caches are most useful for read-only or

read-mostly data. They may reduce performance for queries with highly

dynamic results.

• Both server-side and client result set caches use memory. So, caching very

large result sets can cause performance problems.

20.4.1 Server-Side Result Set Cache

Support for server-side Result Set caching has been introduced for both JDBC Thin and

JDBC Oracle Call Interface (OCI) drivers since Oracle Database 11g Release 1. The server-

side result cache is used to cache the results of the current queries, query fragments, and

PL/SQL functions in memory and then to use the cached results in future executions of the

query, query fragment, or PL/SQL function. The cached results reside in the result cache

memory portion of the SGA. A cached result is automatically invalidated whenever a

database object used in its creation is successfully modified. The server-side caching can be

of the following two types:

• SQL Query Result Cache

• PL/SQL Function Result Cache

Chapter 20

About Result Set Caching

20-13

See Also:

• Oracle Database Performance Tuning Guide for more information about

SQL Query Result Cache

• Oracle Database PL/SQL Language Reference for more information

about PL/SQL Function Result Cache

20.4.2 Client-Side Result Set Cache

Client-side result set cache feature enables client-side caching of SQL query result

sets in client memory. In this way, the applications can use client memory to take

advantage of the client-side result set cache to improve response times of repetitive

queries.

This section covers the following topics:

• Enabling the Client-Side Result Set Cache

• Benefits of Client-Side Result Set Cache

• Usage Guidelines in JDBC

20.4.2.1 Enabling the Client-Side Result Set Cache

Oracle Database Release 18c supports client-side result set cache in the JDBC thin

driver. You can use the new

oracle.jdbc.enableQueryResultCache

connection

property for enabling this feature. The default value of this property is

true

, which

means that this feature is enabled by default. You can disable this feature by setting

the property to

false

Note:

• In Oracle Database 12c Release 2 (12.2), the

enableQueryResultCache

property is available as

enableResultSetCache

, and the default value is

false

. You can enable this feature by setting the

enableResultSetCache

property to

true

• The JDBC OCI driver supports client-side result set cache already.

See Also:

Oracle Call Interface Programmer's Guide

Chapter 20

About Result Set Caching

20-14

For using this feature, you must set the following database initialization parameters in the

following way:

CLIENT_RESULT_CACHE_SIZE=100M

CLIENT_RESULT_CACHE_LAG=1000

This value of the

CLIENT_RESULT_CACHE_SIZE

parameter controls how much memory the thin

driver can use for its cache.

A read-only or read-mostly table can then be annoted and its data can be cached on the

driver. For example,

RESULT_CACHE(MODE FORCE)

You can also use a SQL hint

/*+RESULT_CACHE */

for identifying queries that are eligible for

caching.

See Also:

Oracle Database JDBC Java API Reference

20.4.2.2 Benefits of Client-Side Result Set Cache

The benefits of the client-side result set cache are the following:

• The client-side result set cache is completely transparent to the applications and its

cache of result set data is kept consistent with any session or database changes that

affect its result set.

• Table annotation makes client-side result set work transparently to the JDBC

applications. Otherwise, you must use a hint to enable it. The cache hit avoids the

execution of the query and roundtrip to the server to get the result sets. This can result in

huge performance savings for server resources, for example, server CPU and server I/O.

See Also:

Table Annotations and SQL Hints

• The result cache on the client is per-process, so multiple client sessions can

simultaneously use matching cached result sets.

• The result cache on the client minimizes the need for each application to have its own

custom result set cache.

• The result cache on the client uses the client memory that is cheaper than server

memory.

20.4.2.3 Usage Guidelines in JDBC

You can enable result set caching in the following three ways:

• RESULT_CACHE_MODE Parameter

• Table Annotations

• SQL Hints

Chapter 20

About Result Set Caching

20-15

Note:

• You must use JDBC statement caching or cache statements at the

application level when using the client-side result set cache.

• The SQL hints take precedence over the session parameter

RESULT_CACHE_MODE

and table annotations. The table annotation

FORCE

takes precedence over session parameter.

Related Topics

• Statement and Result Set Caching

20.4.2.3.1 RESULT_CACHE_MODE Parameter

You can use the

RESULT_CACHE_MODE

parameter to decide the result cache mode

across tables in your queries. Use this clause with the

ALTER SESSION

and

ALTER

SYSTEM

statements, or inside the server parameter file (

init.ora

) to determine result

caching. You can set the

RESULT_CACHE_MODE

parameter to control whether the SQL

query result cache is used for all queries, or only for the queries that are annotated

with the result cache hint using SQL hints or table annotations.

20.4.2.3.2 Table Annotations

You can use table annotations to enable result caching without making changes to the

code. The

ALTER TABLE

and

CREATE TABLE

statements enable you to annotate tables

with result cache mode. The syntax is:

CREATE|ALTER TABLE [<schema>.]<table> ... [RESULT_CACHE (MODE {FORCE|DEFAULT})]

Following example shows how to use table annotations with

CREATE TABLE

statements:

CREATE TABLE foo (a NUMBER, b VARCHAR2(20)) RESULT_CACHE (MODE FORCE);

Following example shows how to use table annotations with

ALTER TABLE

statements:

ALTER TABLE foo RESULT_CACHE (MODE DEFAULT);

20.4.2.3.3 SQL Hints

You can use SQL hints to specify the queries to be cached by annotating the queries

with a

/*+ result_cache */

or /*+ no_result_cache */ hint. For example, look at the

following code snippet:

String query = "select /*+ result_cache */ * from employees where employee_id

< : 1";

((oracle.jdbc.OracleConnection)conn).setImplicitCachingEnabled(true);

((oracle.jdbc.OracleConnection)conn).setStatementCacheSize(10);

PreparedStatement pstmt;

ResultSet rs;

for (int j = 0 ; j < 10 ; j++ )

{

pstmt = conn.prepareStatement (query);

pstmt.setInt(1,7500);

rs = pstmt.executeQuery();

Chapter 20

About Result Set Caching

20-16

while (rs.next( ) )

{ // see the values }

rs.close;

pstmt.close( ) ;

}

In the preceding example, the client result cache hint

/*+ result_cache */

is annotated to

the actual query, that is,

select * from employees where employee_id < : 1

. So, the first

execution of the query goes to the database and the result set is cached for the remaining

nine executions of the query. This improves the performance of your application significantly.

This is primarily useful for read-only data.

Following are some more examples of SQL hints. All the following examples assume that the

dept

table is annotated for result caching by using the following command:

ALTER TABLE dept result_cache (MODE FORCE);

Examples

• SELECT * FROM employees

The result set will not be cached.

• SELECT * FROM departments

The result set will be cached.

• SELECT /*+ result_cache */ employee_id FROM employees

The result set will be cached.

• SELECT /*+ no_result_cache */ department_id FROM departments

The result set will not be cached.

• SELECT /*+ result_cache */ * FROM departments

The result set will be cached though query hint is not necessary.

• SELECT e.first_name FROM employees e, departments d WHERE e.department_id =

d.department_id

The result set will not be cached because neither is a query hint available nor are all the

tables annotated as

FORCE

Note:

For information about usage guidelines, Client cache consistency, Deployment Time

settings, Client cache Statistics, Validation of client result cache, and OCI Client

Result Cache and Server Result Cache, refer to the Oracle Call Interface

Programmer's Guide.

Chapter 20

About Result Set Caching

20-17

Performance Extensions

This chapter describes the Oracle performance extensions to the Java Database Connectivity

(JDBC) standard.

This chapter covers the following topics:

• Update Batching

• Additional Oracle Performance Extensions

Note:

Oracle update batching was deprecated in Oracle Database 12c Release 1 (12.1).

Starting in Oracle Database 12c Release 2 (12.2), Oracle update batching is a no

operation code (no-op). This means that if you implement Oracle update batching in

your application, using the Oracle Database 12c Release 2 (12.2) JDBC driver, then

the specified batch size is not set and results in a batch size of 1. With this batch

setting, your application processes one row at a time. Oracle strongly recommends

that you use the standard JDBC batching if you are using the Oracle Database 12c

Release 2 (12.2) JDBC driver.

21.1 Update Batching

This section covers the following topics:

• Overview of Update Batching

• Standard Update Batching

• Premature Batch Flush

21.1.1 Overview of Update Batching

You can reduce the number of round-trips to the database, thereby improving application

performance, by grouping multiple

UPDATE

DELETE

, or

INSERT

statements into a single batch

and having the whole batch sent to the database and processed in one trip. This is referred to

as 'update batching'. This is especially useful with prepared statements, when you are

repeating the same statement with different bind variables.

21-1

Note:

• The JDBC 2.0 specification refers to 'update batching' as 'batch updates'.

• To adhere to the JDBC 2.0 standard, Oracle implementation of standard

update batching supports callable statements without

OUT

parameters,

generic statements, and prepared statements. You can migrate standard

update batching into an Oracle JDBC application without difficulty.

However, the Oracle implementation of standard update batching does

not implement true batching for generic statements and callable

statements and you will see performance improvement for only

PreparedStatement

objects.

21.1.2 Standard Update Batching

JDBC standard update batching depends on explicitly adding statements to the batch

using an

addBatch

method and explicitly processing the batch using an

executeBatch

method.

Note:

Disable auto-commit mode when you use update batching. In case an error

occurs while you are processing a batch, this provides you the option of

committing or rolling back the operations that ran successfully prior to the

error.

21.1.2.1 Limitations in the Oracle Implementation of Standard Batching

This section discusses the limitations and implementation details regarding the Oracle

implementation of standard update batching.

In Oracle JDBC applications, update batching is intended for use with prepared

statements that are being processed repeatedly with different sets of bind values.

The Oracle implementation of standard update batching does not implement true

batching for generic statements and callable statements. Even though Oracle JDBC

supports the use of standard batching for

Statement

and

CallableStatement

objects,

you are unlikely to see performance improvement.

21.1.2.2 About Adding Operations to the Batch

When any statement object is first created, its statement batch is empty. Use the

standard

addBatch

method to add an operation to the statement batch. This method is

specified in the standard

java.sql.Statement

PreparedStatement

, and

CallableStatement

interfaces, which are implemented by the

oracle.jdbc.OracleStatement

OraclePreparedStatement

, and

OracleCallableStatement

interfaces, respectively.

Chapter 21

Update Batching

21-2

For a

Statement

object, the

addBatch

method takes a Java

String

with a SQL operation as

input. For example:

...

Statement stmt = conn.createStatement();

stmt.addBatch("INSERT INTO emp VALUES(1000, 'Joe Jones')");

stmt.addBatch("INSERT INTO dept VALUES(260, 'Sales')");

stmt.addBatch("INSERT INTO emp_dept VALUES(1000, 260)");

...

At this point, three operations are in the batch.

For prepared statements, update batching is used to batch multiple runs of the same

statement with different sets of bind parameters. For a

PreparedStatement

OraclePreparedStatement

object, the

addBatch

method takes no input. It simply adds the

operation to the batch using the bind parameters last set by the appropriate

setXXX

methods.

This is also true for

CallableStatement

OracleCallableStatement

objects, but remember

that in the Oracle implementation of standard update batching, you will probably see no

performance improvement in batching callable statements.

For example:

...

PreparedStatement pstmt =

conn.prepareStatement("INSERT INTO employees VALUES(?, ?)");

pstmt.setInt(1, 2000);

pstmt.setString(2, "Milo Mumford");

pstmt.addBatch();

pstmt.setInt(1, 3000);

pstmt.setString(2, "Sulu Simpson");

pstmt.addBatch();

...

At this point, two operations are in the batch.

Because a batch is associated with a single prepared statement object, you can batch only

repeated runs of a single prepared statement, as in this example.

21.1.2.3 About Processing the Batch

To process the current batch of operations, use the

executeBatch

method of the statement

object. This method is specified in the standard

Statement

interface, which is extended by the

standard

PreparedStatement

and

CallableStatement

interfaces.

Chapter 21

Update Batching

21-3

Note:

If you add too many operations to a batch by calling the

addBatch

method

several times and create a very large batch (for example, with more than or

equal to 100,000 rows), then while calling the

executeBatch

method on the

whole batch, you may face severe performance problems in terms of

memory. To avoid this issue, the JDBC driver transparently breaks up the

large batches into smaller internal batches and makes a roundtrip to the

server for each internal batch. This makes your application slightly slower

because of each round-trip overhead, but optimizes memory significantly.

However, if each bound row is very large in size (for example, more than

about 1MB each or so), then this process can impact the overall performance

negatively because in such a case, the performance gained in terms of

memory will be less than the performance lost in terms of time.

Following is an example that repeats the prepared statement

addBatch

calls shown

previously and then processes the batch:

...

PreparedStatement pstmt =

conn.prepareStatement("INSERT INTO employees VALUES(?, ?)");

pstmt.setInt(1, 2000);

pstmt.setString(2, "Milo Mumford");

pstmt.addBatch();

pstmt.setInt(1, 3000);

pstmt.setString(2, "Sulu Simpson");

pstmt.addBatch();

int[] updateCounts = pstmt.executeBatch();

...

21.1.2.4 Row Count per Iteration for Array DMLs

Starting from Oracle Database 12c Release 1 (12.1), the

executeBatch

method has

been improved so that it returns an int array of size that is the same as the number of

records in the batch and each item in the return array is the number of database table

rows affected by the corresponding record of the batch. For example, if the batch size

is 5, then the

executeBatch

method returns an array of size 5. In case of an error in

between execution of the batch, the

executeBatch

method cannot return a value,

instead it throws a

BatchUpdateException

. In this case, the exception itself carries an

int array of size

as its data, where

is the number of successful record executions.

For example, if the batch is of size 5 and the error occurs at the 4th record, then the

BatchUpdateException

has an array of size 3 (3 records executed successfully) and

each item in the array represents how many rows were affected by each of them.

21.1.2.5 About Committing the Changes in the Oracle Implementation of

Standard Batching

After you process the batch, you must still commit the changes, presuming auto-

commit is disabled as recommended.

Chapter 21

Update Batching

21-4

Calling

commit

, commits nonbatched operations and batched operations for statement

batches that have been processed, but for the Oracle implementation of standard batching,

has no effect on pending statement batches that have not been processed.

21.1.2.6 About Clearing the Batch

To clear the current batch of operations instead of processing it, use the

clearBatch

method

of the statement object. This method is specified in the standard

Statement

interface, which

is extended by the standard

PreparedStatement

and

CallableStatement

interfaces.

Keep the following things in mind:

• When a batch is processed, operations are performed in the order in which they were

batched.

• After calling

addBatch

, you must call either

executeBatch

clearBatch

before a call to

executeUpdate

, otherwise there will be a SQL exception.

• A

clearBatch

executeBatch

call resets the statement batch to empty.

• The statement batch is not reset to empty if the connection receives a

ROLLBACK

request.

You must explicitly call

clearBatch

to reset it.

• Invoking

clearBatch

method after a rollback works for all releases.

• An

executeBatch

call closes the current result set of the statement object, if one exists.

• Nothing is returned by the

clearBatch

method.

Following is an example that repeats the prepared statement

addBatch

calls shown

previously but then clears the batch under certain circumstances:

...

PreparedStatement pstmt =

conn.prepareStatement("INSERT INTO employees VALUES(?, ?)");

pstmt.setInt(1, 2000);

pstmt.setString(2, "Milo Mumford");

pstmt.addBatch();

pstmt.setInt(1, 3000);

pstmt.setString(2, "Sulu Simpson");

pstmt.addBatch();

if (...condition...)

{

int[] updateCounts = pstmt.executeBatch();

...

}

else

{

pstmt.clearBatch();

...

}

21.1.2.7 Update Counts in the Oracle Implementation of Standard Batching

If a statement batch is processed successfully, then the integer array, or update counts array,

returned by the statement

executeBatch

call will always have one element for each operation

Chapter 21

Update Batching

21-5

in the batch. In the Oracle implementation of standard update batching, the values of

the array elements are as follows:

• For a prepared statement batch, the array contains the actual update counts

indicating the number of rows affected by each operation.

• For a generic statement batch, the array contains the actual update counts

indicating the number of rows affected by each operation. The actual update

counts can be provided only in the case of generic statements in the Oracle

implementation of standard batching.

• For a callable statement batch, the array contains the actual update counts

indicating the number of rows affected by each operation.

In your code, upon successful processing of a batch, you should be prepared to

handle either

-2

, or true update counts in the array elements. For a successful batch

processing, the array contains either all

-2

, or all positive integers.

Example 21-1 illustrates the use of standard update batching.

Example 21-1 Standard Update Batching

This example combines the sample fragments in the previous sections, accomplishing

the following steps:

1. Disabling auto-commit mode, which you should always perform when using

update batching

2. Creating a prepared statement object

3. Adding operations to the batch associated with the prepared statement object

4. Processing the batch

5. Committing the operations from the batch

conn.setAutoCommit(false);

PreparedStatement pstmt =

conn.prepareStatement("INSERT INTO employees VALUES(?, ?)");

pstmt.setInt(1, 2000);

pstmt.setString(2, "Milo Mumford");

pstmt.addBatch();

pstmt.setInt(1, 3000);

pstmt.setString(2, "Sulu Simpson");

pstmt.addBatch();

int[] updateCounts = pstmt.executeBatch();

conn.commit();

pstmt.close();

...

You can process the update counts array to determine if the batch processed

successfully.

Chapter 21

Update Batching

21-6

21.1.2.8 Error Handling in the Oracle Implementation of Standard Batching

If any one of the batched operations fails to complete successfully or attempts to return a

result set during an

executeBatch

call, then the processing stops and a

java.sql.BatchUpdateException

is generated.

After a batch exception, the update counts array can be retrieved using the

getUpdateCounts

method of the

BatchUpdateException

object. This returns an

int

array of update counts, just

as the

executeBatch

method does. In the Oracle implementation of standard update

batching, contents of the update counts array are as follows, after a batch is processed:

• For a prepared statement batch, in case of an error in between execution of the batch,

the

executeBatch

method cannot return a value, instead it throws a

BatchUpdateException

. In this case, the exception itself carries an int array of size

its data, where

is the number of successful record executions. For example, if the batch

is of size 5 and the error occurs at the 4th record, then the

BatchUpdateException

has an

array of size 3 (3 records executed successfully) and each item in the array represents

how many rows were affected by each of them.

• For a generic statement batch or callable statement batch, the update counts array is

only a partial array containing the actual update counts up to the point of the error. The

actual update counts can be provided because Oracle JDBC cannot use true batching for

generic and callable statements in the Oracle implementation of standard update

batching.

For example, if there were 20 operations in the batch, the first 13 succeeded, and the

14th generated an exception, then the update counts array will have 13 elements,

containing actual update counts of the successful operations.

You can either commit or roll back the successful operations in this situation, as you

prefer.

In your code, upon failed processing of a batch, you should be prepared to handle either

-3

or true update counts in the array elements when an exception occurs. For a failed batch

processing, you will have either a full array of

-3

or a partial array of positive integers.

21.1.2.9 About Intermixing Batched Statements and Nonbatched Statements

You cannot call

executeUpdate

for regular, nonbatched processing of an operation if the

statement object has a pending batch of operations.

However, you can intermix batched operations and nonbatched operations in a single

statement object if you process nonbatched operations either prior to adding any operations

to the statement batch or after processing the batch. Essentially, you can call

executeUpdate

for a statement object only when its update batch is empty. If the batch is non-empty, then an

exception will be generated.

For example, it is valid to have a sequence, such as the following:

...

PreparedStatement pstmt =

conn.prepareStatement("INSERT INTO employees VALUES(?, ?)");

pstmt.setInt(1, 2000);

pstmt.setString(2, "Milo Mumford");

int scount = pstmt.executeUpdate(); // OK; no operations in pstmt batch

Chapter 21

Update Batching

21-7

pstmt.setInt(1, 3000);

pstmt.setString(2, "Sulu Simpson");

pstmt.addBatch(); // Now start a batch

pstmt.setInt(1, 4000);

pstmt.setString(2, "Stan Leland");

pstmt.addBatch();

int[] bcounts = pstmt.executeBatch();

pstmt.setInt(1, 5000);

pstmt.setString(2, "Amy Feiner");

int scount = pstmt.executeUpdate(); // OK; pstmt batch was executed

...

Intermixing nonbatched operations on one statement object and batched operations

on another statement object within your code is permissible. Different statement

objects are independent of each other with regard to update batching operations. A

COMMIT

request will affect all nonbatched operations and all successful operations in

processed batches, but will not affect any pending batches.

21.1.3 Premature Batch Flush

Premature batch flush happens due to a change in cached metadata. Cached

metadata can be changed due to various reasons, such as the following:

• The initial bind was null and the following bind is not null.

• A scalar type is initially bound as string and then bound as scalar type or the

reverse.

The premature batch flush count is summed to the return value of the next

executeUpdate

sendBatch

method.

The old functionality lost all these batch flush values which can be obtained now. To

switch back to the old functionality, you can set the

AccumulateBatchResult

property

false

, as follows:

java.util.Properties info = new java.util.Properties();

info.setProperty("user", "HR");

info.setProperty("passwd", "hr");

// other properties

...

// property: batch flush type

info.setProperty("AccumulateBatchResult", "false");

OracleDataSource ods = new OracleDataSource();

ods.setConnectionProperties(info);

ods.setURL("jdbc:oracle:oci:@"");

Connection conn = ods.getConnection();

Note:

The

AccumulateBatchResult

property is set to

true

by default.

Chapter 21

Update Batching

21-8

Example 21-2 illustrates premature batch flushing.

Example 21-2 Premature Batch Flushing

((OraclePreparedStatement)pstmt).setExecuteBatch (2);

pstmt.setNull(1, OracleTypes.NUMBER);

pstmt.setString(2, "test11");

int count = pstmt.executeUpdate(); // returns 0

* Premature batch flush happens here.

pstmt.setInt(1, 22);

pstmt.setString(2, "test22");

int count = pstmt.executeUpdate(); // returns 0

pstmt.setInt(1, 33);

pstmt.setString(2, "test33");

* returns 3 with the new batching scheme where as,

* returns 2 with the old batching scheme.

int count = pstmt.executeUpdate();

21.2 Additional Oracle Performance Extensions

In addition to update batching, Oracle JDBC drivers support the extensions discussed in this

chpter, which improve performance by reducing round-trips to the database:

• Prefetching rows

This reduces round-trips to the database by fetching multiple rows of data each time data

is fetched. The extra data is stored in client-side buffers for later access by the client. The

number of rows to prefetch can be set as desired.

• Specifying column types

This avoids an inefficiency in the standard JDBC protocol for performing and returning

the results of queries.

• Suppressing database metadata

TABLE_REMARKS

columns

This avoids an expensive outer join operation.

Oracle provides several extensions to connection properties objects to support these

performance extensions. These extensions enable you to set the

remarksReporting

flag and

default values for row prefetching and update batching.

This section covers the following topics:

• Oracle Row-Prefetching Limitations

• About Defining Column Types

• About Reporting DatabaseMetaData TABLE_REMARKS

Chapter 21

Additional Oracle Performance Extensions

21-9

21.2.1 Oracle Row-Prefetching Limitations

There is no maximum prefetch setting. The default value is 10. Larger or smaller

values may be appropriate depending on the number of rows and columns expected

from the query. You can set the default connection row-prefetch value using a

Properties

object.

When a statement object is created, it receives the default row-prefetch setting from

the associated connection. Subsequent changes to the default connection row-

prefetch setting will have no effect on the statement row-prefetch setting.

If a column of a result set is of data type

LONG

RAW

LOB

s returned through the

data interface, that is, the streaming types, then JDBC changes the statement row-

prefetch setting to 1, even if you never actually read a value of either of these types.

Setting the prefetch size can affect the performance of an application. Increasing the

prefetch size will reduce the number of round-trips required to get all the data, but will

increase memory usage. This will depend on the number and size of the columns in

the query and the number of rows expected to be returned. It will also depend on the

memory and CPU loading of the JDBC client machine. The optimum for a standalone

client application will be different from a heavily loaded application server. The speed

and latency of the network connection should also be considered.

Note:

Starting from Oracle Database 11g Release 1, the Thin driver can fetch the

first

prefetch_size

number of rows from the server in the very first round-

trip. This saves one round-trip in SELECT statements.

If you are migrating an application from earlier releases of Oracle JDBC drivers to 10g

Release 1 (10.1) or later releases of Oracle JDBC drivers, then you should revisit the

optimizations that you had done earlier, because the memory usage and performance

characteristics may have changed substantially.

A common situation that you may encounter is, say, you have a query that selects a

unique key. The query will return only zero or one row. Setting the prefetch size to 1

will decrease memory and CPU usage and cannot increase round-trips. However, you

must be careful to avoid the error of requesting an extra fetch by writing

while(rs.next())

instead of

if(rs.next())

If you are using the JDBC Thin driver, then use the

useFetchSizeWithLongColumn

connection property, because it will perform

PARSE

EXECUTE

, and

FETCH

in a single

round-trip.

Tuning of the prefetch size should be done along with tuning of memory management

in your JVM under realistic loads of the actual application.

Chapter 21

Additional Oracle Performance Extensions

21-10

Note:

• Do not mix the JDBC 2.0 fetch size application programming interface (API)

and the Oracle row-prefetching API in your application. You can use one or the

other, but not both.

• Be aware that setting the Oracle fetch size value can affect not only queries, but

also explicitly refetching rows in a result set through the result set

refreshRow

method, which is relevant for scroll-sensitive/read-only, scroll-sensitive/

updatable, and scroll-insensitive/updatable result sets, and the window size of a

scroll-sensitive result set, affecting how often automatic refetches are

performed. However, the Oracle fetch size value will be overridden by any

setting of the fetch size.

21.2.2 About Defining Column Types

Note:

Starting from Oracle Database 12c Release 1 (12.1), the

defineColumnType

method is deprecated.

The implementation of

defineColumnType

changed significantly since Oracle Database 10g.

Previously,

defineColumnType

was used both as a performance optimization and to force

data type conversion. In previous releases, all of the drivers benefited from calls to

defineColumnType

. Starting from Oracle Database 10g, the JDBC Thin driver no longer

needs the information provided. The JDBC Thin driver achieves maximum performance

without calls to

defineColumnType

. The JDBC Oracle Call Interface (OCI) and server-side

internal drivers still get better performance when the application uses

defineColumnType

If your code is used with both the JDBC Thin and OCI drivers, you can disable the

defineColumnType

method when using the Thin driver by setting the connection property

disableDefineColumnType

true

. Doing this makes

defineColumnType

have no effect. Do

not set this connection property to

true

when using the JDBC OCI or server-side internal

drivers.

You can also use

defineColumnType

to control how much memory the client-side allocates or

to limit the size of variable-length data.

Follow these general steps to define column types for a query:

1. If necessary, cast your statement object to

OracleStatement

OraclePreparedStatement

OracleCallableStatement

, as applicable.

2. If necessary, use the

clearDefines

method of your

Statement

object to clear any

previous column definitions for this

Statement

object.

3. On each column, call the

defineColumnType

method of your

Statement

object, passing it

these parameters:

• Column index (integer)

• Type code (integer)

Chapter 21

Additional Oracle Performance Extensions

21-11

Use the

static

constants of the

java.sql.Types

class or

oracle.jdbc.OracleTypes

class, such as

Types.INTEGER

Types.FLOAT

Types.VARCHAR

OracleTypes.VARCHAR

, and

OracleTypes.ROWID

. Type codes

for standard types are identical in these two classes.

• Type name (string)

For structured objects, object references, and arrays, you must also specify

the type name. For example,

Employee

EmployeeRef

, or

EmployeeArray

• Maximum field size (integer)

Optionally specify a maximum data length for this column.

You cannot specify a maximum field size parameter if you are defining the

column type for a structured object, object reference, or array. If you try to

include this parameter, it will be ignored.

• Form of use (short)

Optionally specify a form of use for the column. This can be

OraclePreparedStatement.FORM_CHAR

to use the database character set or

OraclePreparedStatement.FORM_NCHAR

to use the national character set. If

this parameter is omitted, the default is

FORM_CHAR

For example, assuming

stmt

is an Oracle statement, use:

stmt.defineColumnType(column_index, typeCode);

If the column is

VARCHAR

or equivalent and you know the length limit:

stmt.defineColumnType(column_index, typeCode, max_size);

For an

NVARCHAR

column where the original maximum length is desired and

conversion to the database character set is requested:

stmt.defineColumnType(column_index, typeCode, 0,

OraclePreparedStatement.FORM_CHAR );

For structured object, object reference, and array columns:

stmt.defineColumnType(column_index, typeCode, typeName);

Set a maximum field size if you do not want to receive the full default length of the

data. Calling the

setMaxFieldSize

method of the standard JDBC

Statement

class

sets a restriction on the amount of data returned. Specifically, the size of the data

returned will be the minimum of the following:

• The maximum field size set in

defineColumnType

• The maximum field size set in

setMaxFieldSize

• The natural maximum size of the data type

After you complete these steps, use the

executeQuery

method of the statement to

perform the query.

Chapter 21

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21-12

Note:

It is no longer necessary to specify a data type for each column of the expected

result set.

The following example illustrates the use of this feature. It assumes you have imported the

oracle.jdbc.*

interfaces.

Example 21-3 Defining Column Types

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:thin:@localhost:5221:orcl");

ods.setUser("HR");

ods.setPassword("hr");

Connection conn = ods.getConnection();

Statement stmt = conn.createStatement();

// Allocate only 2 chars for this column (truncation will happen)

((OracleStatement)stmt).defineColumnType(1, Types.VARCHAR, 2);

ResultSet rset = stmt.executeQuery("select ename from emp");

while(rset.next() )

System.out.println(rset.getString(1));

stmt.close();

As this example shows, you must cast the

Statement

object,

stmt

, to

OracleStatement

in the

invocation of the

defineColumnType

method. The

createStatement

method of the connection

returns an object of type

java.sql.Statement

, which does not have the

defineColumnType

and

clearDefines

methods. These methods are provided only in the

OracleStatement

implementation.

The define-extensions use JDBC types to specify the desired types. The allowed define types

for columns depend on the internal Oracle type of the column.

All columns can be defined to their natural JDBC types. In most cases, they can be defined to

the

Types.CHAR

Types.VARCHAR

type code.

The following table lists the valid column definition arguments that you can use in the

defineColumnType

method.

Table 21-1 Valid Column Type Specifications

If the column has Oracle SQL

type:

You can use defineColumnType to define it as:

NUMBER

VARNUM BIGINT

TINYINT

SMALLINT

INTEGER

FLOAT

REAL

DOUBLE

NUMERIC

DECIMAL

CHAR

VARCHAR

CHAR

VARCHAR2 CHAR

VARCHAR

LONG CHAR

VARCHAR

LONGVARCHAR

LONGRAW LONGVARBINARY

VARBINARY

BINARY

RAW VARBINARY

BINARY

DATE DATE

TIME

TIMESTAMP

CHAR

VARCHAR

ROWID ROWID

Chapter 21

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Table 21-1 (Cont.) Valid Column Type Specifications

If the column has Oracle SQL

type:

You can use defineColumnType to define it as:

BLOB VARBINARY

BINARY

CLOB LONG

CHAR

VARCHAR

It is always valid to use

defineColumnType

with the original data type of the column.

21.2.3 About Reporting DatabaseMetaData TABLE_REMARKS

The

getColumns

getProcedureColumns

getProcedures

, and

getTables

methods of

the database metadata classes are slow if they must report

TABLE_REMARKS

columns,

because this necessitates an expensive outer join. For this reason, the JDBC driver

does not report

TABLE_REMARKS

columns by default.

You can enable

TABLE_REMARKS

reporting by passing a

true

argument to the

setRemarksReporting

method of an

OracleConnection

object.

Equivalently, instead of calling

setRemarksReporting

, you can set the

remarksReporting

Java property if you use a Java

Properties

object in establishing

the connection.

If you are using a standard

java.sql.Connection

object, you must cast it to

OracleConnection

to use

setRemarksReporting

The following code snippet illustrates how to enable

TABLE_REMARKS

reporting:

((oracle.jdbc.OracleConnection)conn ).setRemarksReporting(true);

Here,

conn

is the name of your standard

Connection

object, the following statement

enables

TABLE_REMARKS

reporting:

Considerations for getColumns

By default, the

getColumns

method does not retrieve information about the columns if

a synonym is specified. To enable the retrieval of information if a synonym is specified,

you must call the

setIncludeSynonyms

method on the connection as follows:

((oracle.jdbc.OracleConnection)conn ).setIncludeSynonyms(true)

This will cause all subsequent

getColumns

method calls on the connection to include

synonyms. This is similar to

setRemarksReporting

. Alternatively, you can set the

includeSynonyms

connection property. This is similar to the

remarksReporting

connection property.

However, bear in mind that if

includeSynonyms

true

, then the name of the object

returned in the

table_name

column will be the synonym name, if a synonym exists.

This is true even if you pass the table name to

getColumns

Considerations for getProcedures and getProcedureColumns Methods

According to JDBC versions 1.1 and 1.2, the methods

getProcedures

and

getProcedureColumns

treat the

catalog

schemaPattern

columnNamePattern

, and

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21-14

procedureNamePattern

parameters in the same way. In the Oracle definition of these

methods, the parameters are treated differently:

•

catalog

Oracle does not have multiple catalogs, but it does have packages. Consequently, the

catalog

parameter is treated as the package name. This applies both on input, which is

the

catalog

parameter, and the output, which is the

catalog

column in the returned

ResultSet

. On input, the construct

, which is an empty string, retrieves procedures

and arguments without a package, that is, standalone objects. A

null

value means to

drop from the selection criteria, that is, return information about both standalone and

packaged objects. That is, it has the same effect as passing in the percent sign (

Otherwise, the

catalog

parameter should be a package name pattern, with SQL wild

cards, if desired.

•

schemaPattern

All objects within Oracle database must have a schema, so it does not make sense to

return information for those objects without one. Thus, the construct

, which is an

empty string, is interpreted on input to mean the objects in the current schema, that is,

the one to which you are currently connected. To be consistent with the behavior of the

catalog

parameter,

null

is interpreted to drop the schema from the selection criteria.

That is, it has the same effect as passing in

. It can also be used as a pattern with SQL

wild cards.

•

procedureNamePattern

and

columnNamePattern

The empty string (" ") does not make sense for either parameter, because all procedures

and arguments must have names. Thus, the construct

will raise an exception. To be

consistent with the behavior of other parameters,

null

has the same effect as passing in

percent sign (

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21-15

JDBC Reactive Extensions

The Reactive Extensions are a set of methods that extend the JDBC standard to offer

asynchronous database access.

The Reactive Extensions use non-blocking mechanisms for creating connection objects,

executing SQL statements, fetching rows, committing transactions, rolling back transactions,

closing Connection objects, and reading and writing BFILEs, BLOBs, and CLOBs.

This chapter includes the following topics:

• Overview of JDBC Reactive Extensions

• About Building an Application with Reactive Extensions

• Threading Model of Asynchronous Methods

• About the Flow API

• Using the FlowAdapters Class

• Streaming Row Data with the Reactor Library

• Streaming Row Data with the RxJava Library

• Streaming Row Data with the Akka Streams Library

• Limitations of JDBC Reactive Extensions

22.1 Overview of JDBC Reactive Extensions

The Reactive Extensions implement the Publisher and Subscriber types defined by the

java.util.concurrent.Flow

interfaces, which is the standard JDK representation of a

reactive stream.

The Reactive Extensions use a single Java NIO Selector for nonblocking Database

operations.

Requirements for Using JDBC Reactive Extensions

For using the JDBC Reactive Extensions, you must use the following:

• JDBC Thin Driver 21c or later for building connections

• JDK 11

•

ojdbc11.jar

Architecture of JDBC Reactive Extensions

The following diagram illustrates the architecture of applications using JDBC Reactive

Extensions:

22-1

Figure 22-1 Architecture of Applications Using JDBC Reactive Extensions

Java

Application

Converged

Database

Third-Party

Reactive

Streams

Libraries

Reactive

Relational

Database

Connectivity

(R2DBC)

JDBC

Reactive

Extension

(Implements

Java Flow

API)

Oracle

JDBC

Fully Reactive Streams

Synchronous calls

Asynchronous calls with non blocking I/O

22.2 About Building an Application with Reactive Extensions

This section describes the steps that you must follow to build an application using the

Reactive Extensions.

Building an application using the Reactive Extensions involves the same steps as

building an application using the standard methods. But, in case of Reactive

Extensions, you use the new asynchronous methods. This section describes how to

use the various asynchronous methods in the following sections:

• Opening a Connection Using Asynchronous Methods

• Execution of SQL Statements with Asynchronous Methods

• About Fetching Row Data with Asynchronous Methods

• Reading LOB Data Using Asynchronous Methods

• Writing LOB Data Using Asynchronous Methods

• Committing a Transaction Using Asynchronous Methods

• Closing a Connection Using Asynchronous Methods

22.2.1 Opening a Connection Using Asynchronous Methods

The

OracleConnectionBuilder

interface provides methods for opening a connection

asynchronously.

The

OracleConnectionBuilder.buildConnectionPublisherOracle

method returns a

Flow.Publisher<OracleConnection>

type. The Publisher emits a single Connection to

a Subscriber. Once the Subscriber signals demand, the Publisher asynchronously

opens a new Connection. The Published Connection is identical to a Connection that

you can build using the

ConnectionBuilder.build

method.

The following example demonstrates how to asynchronously open a connection.

/**

* Asynchronously opens a new connection

* @param dataSource Datasource configured with a URL, User, and

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22-2

Password

* @return A Publisher that emits a single connection

* @throws SQLException If a database access error occurs before the

* connection can be opened

Flow.Publisher<OracleConnection> openConnection(DataSource dataSource)

throws SQLException {

return dataSource.unwrap(OracleDataSource.class)

.createConnectionBuilder()

.buildConnectionPublisherOracle();

}

22.2.2 Execution of SQL Statements with Asynchronous Methods

This section describes how to execute SQL statements with asynchronous methods.

The

OraclePreparedStatement

interface exposes methods for asynchronous SQL execution.

Each asynchronous method performs a function that is analogous to the corresponding

synchronous method of SQL execution. This relationship is expressed in the following table:

Table 22-1 Method Comparison

Synchronous Method Asynchronous Method

boolean execute Flow.Publisher<Boolean>

executeAsyncOracle

long executeLargeUpdate Flow.Publisher<Long>

executeUpdateAsyncOracle

long[] executeLargeBatch Flow.Publisher<Long>

executeBatchAsyncOracle

ResultSet executeQuery Flow.Publisher<OracleResultSet>

executeQueryAsyncOracle

The following sections provide more information about the asynchronous methods:

• Standard SQL Statement Execution with the executeAsyncOracle Method

• DML Statement Execution with the executeUpdateAsyncOracle method

• Batch DML Statement Execution with the executeBatchAsyncOracle Method

• SQL Query Execution with the executeQueryAsyncOracle Method

22.2.2.1 Standard SQL Statement Execution with the executeAsyncOracle Method

This section describes the

executeAsyncOracle

method, which is equivalent to the standard

execute

method.

Any type of SQL statement can be executed by calling the

OraclePreparedStatement.executeAsyncOracle

method. This call returns a

Flow.Publisher<Boolean>

type. The Publisher emits a single Boolean and supports multiple

Subscribers. If the Boolean value is

TRUE

, then it means that the SQL statement has resulted

in row data, which is accessible from the

OraclePreparedStatement.getResultSet

method.

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22-3

If it is

FALSE

, then it means that the SQL statement has returned an update count. The

Boolean result is semantically equivalent to the

boolean

returned by the

execute

method.

/**

* Asynchronously creates a new table by executing a DDL SQL

statement

* @param connection Connection to a database where the table is

created

* @return A Publisher that emits the result of executing DDL SQL

* @throws SQLException If a database access error occurs before the

DDL

* SQL can be executed

Flow.Publisher<Boolean> createTable(Connection connection)

throws SQLException {

PreparedStatement createTableStatement =

connection.prepareStatement(

"CREATE TABLE employee_names (" +

"id NUMBER PRIMARY KEY, " +

"first_name VARCHAR(50), " +

"last_name VARCHAR2(50))");

Flow.Publisher<Boolean> createTablePublisher =

createTableStatement.unwrap(OraclePreparedStatement.class)

.executeAsyncOracle();

createTablePublisher.subscribe(

// This subscriber will close the PreparedStatement

new Flow.Subscriber<Boolean>() {

public void onSubscribe(Flow.Subscription subscription) {

subscription.request(1L);

}

public void onNext(Boolean item) { }

public void onError(Throwable throwable) { closeStatement(); }

public void onComplete() { closeStatement(); }

void closeStatement() {

try { createTableStatement.close(); }

catch (SQLException closeException) { log(closeException); }

}

});

return createTablePublisher;

}

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22.2.2.2 DML Statement Execution with the executeUpdateAsyncOracle method

This section describes the

executeUpdateAsyncOracle

method, which is equivalent to the

standard

executeLargeUpdate

method.

You can use the

OraclePreparedStatement.executeUpdateAsyncOracle

method to execute

single (non-batch) DML statements. This call returns a

Flow.Publisher<Long>

type. The

returned publisher emits a single

Long

value. This

Long

value indicates the number of rows

updated or to be inserted by the DML statement. This

Long

value result is semantically

equivalent to the

long

value returned by the standard

executeLargeUpdate

method.

/**

* Asynchronously updates table data by executing a DML SQL statement

* @param connection Connection to a database where the table data resides

* @return A Publisher that emits the number of rows updated

* @throws SQLException If a database access error occurs before the DML

* SQL can be executed

Flow.Publisher<Long> updateData(Connection connection)

throws SQLException {

PreparedStatement updateStatement = connection.prepareStatement(

"UPDATE employee_names SET " +

"first_name = UPPER(first_name), " +

"last_name = UPPER(last_name)");

Flow.Publisher<Long> updatePublisher =

updateStatement.unwrap(OraclePreparedStatement.class)

.executeUpdateAsyncOracle();

updatePublisher.subscribe(

// This subscriber will close the PreparedStatement

new Flow.Subscriber<Long>() {

public void onSubscribe(Flow.Subscription subscription) {

subscription.request(1L);

}

public void onNext(Long item) { }

public void onError(Throwable throwable) { closeStatement(); }

public void onComplete() { closeStatement(); }

void closeStatement() {

try { updateStatement.close(); }

catch (SQLException closeException) { log(closeException); }

}

});

return updatePublisher;

}

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22.2.2.3 Batch DML Statement Execution with the executeBatchAsyncOracle

Method

This section describes the

executeBatchAsyncOracle

method, which is equivalent to

the standard

executeLargeBatch

method.

You can use the

OraclePreparedStatement.executeBatchAsyncOracle

method to

execute batch DML statements. This call returns a

Flow.Publisher<Long>

type. The

returned publisher emits a

Long

value for each statement in the batch. The

Long

values

indicate the number of rows updated by each DML statement. These

Long

value

results are semantically equivalent to the

long[]

value returned by the standard

executeLargeBatch

method.

/**

* Asynchronously loads table data by executing a batch of DML SQL

statements.

* @param connection Connection to a database where the table data

resides.

* @return A Publisher which emits the number of rows updated.

* @throws SQLException If a database access error occurs before the

DML

* SQL can be executed.

Flow.Publisher<Long> createData(

Connection connection, Iterable<Employee> employeeData)

throws SQLException {

PreparedStatement batchStatement = connection.prepareStatement(

"INSERT INTO employee_names (id, first_name, last_name) " +

"VALUES (?, ?, ?)");

for (Employee employee : employeeData) {

batchStatement.setLong(1, employee.id());

batchStatement.setString(2, employee.firstName());

batchStatement.setString(3, employee.lastName());

batchStatement.addBatch();

}

Flow.Publisher<Long> batchPublisher =

batchStatement.unwrap(OraclePreparedStatement.class)

.executeBatchAsyncOracle();

batchPublisher.subscribe(

// This subscriber will close the PreparedStatement

new Flow.Subscriber<Long>() {

public void onSubscribe(Flow.Subscription subscription) {

subscription.request(Long.MAX_VALUE);

}

public void onNext(Long item) { }

public void onError(Throwable throwable) { closeStatement(); }

public void onComplete() { closeStatement(); }

void closeStatement() {

try { batchStatement.close(); }

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catch (SQLException closeException) { log(closeException); }

}

});

return batchPublisher;

}

22.2.2.4 SQL Query Execution with the executeQueryAsyncOracle Method

This section describes the

executeQueryAsyncOracle

Method, which is equivalent to the

standard

executeQuery

method.

You can execute SQL query statements with the

OraclePreparedStatement.executeQueryAsyncOracle

method. This call returns a

Flow.Publisher<OracleResultSet>

type. The returned publisher emits a single

OracleResultSet

value. The

OracleResultSet

value provides access to row data that is

resulted from the SQL query. This

OracleResultSet

is semantically equivalent to the

ResultSet

returned by the standard

executeQuery

method.

/**

* Asynchronously reads table data by executing a SELECT SQL statement

* @param connection Connection to a database where the table resides

* @return A Publisher that emits the number of rows updated

* @throws SQLException If a database access error occurs before the SELECT

* SQL can be executed

Flow.Publisher<OracleResultSet> readData(Connection connection)

throws SQLException {

PreparedStatement queryStatement = connection.prepareStatement(

"SELECT id, first_name, last_name FROM employee_names");

Flow.Publisher<OracleResultSet> queryPublisher =

queryStatement.unwrap(OraclePreparedStatement.class)

.executeQueryAsyncOracle();

// Close the PreparedStatement after the result set is consumed.

queryStatement.closeOnCompletion();

return queryPublisher;

}

22.2.3 About Fetching Row Data with Asynchronous Methods

This section describes how to fetch row data with asynchronous methods.

The

OracleResultSet

interface exposes the

publisherOracle(Function<OracleRow, T>)

method for asynchronous row data fetching. The argument to this method is a mapping

function for row data. The mapping function is applied to each row of the

ResultSet

. The

method returns a

Flow.Publisher<T>

type, where T is the output type of the mapping

function. The input type of the mapping function is

OracleRow

. An

OracleRow

represents a

single row of the

ResultSet

, and exposes methods to access the column values of that row.

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The following example demonstrates how you can fetch row data with asynchronous

methods:

/**

* Asynchronously fetches table data by from a ResultSet.

* @param resultSet ResultSet which fetches table data.

* @return A Publisher which emits the fetched data as Employee

objects.

* @throws SQLException If a database access error occurs before

table data is

* fetched.

Flow.Publisher<Employee> fetchData(ResultSet resultSet)

throws SQLException {

// Before closing the ResultSet with publisherOracle(..), first

obtain a

// reference to the ResultSet's Statement. The Statement needs to

be closed

// after all data has been fetched.

Statement resultSetStatement = resultSet.getStatement();

Flow.Publisher<Employee> employeePublisher =

resultSet.unwrap(OracleResultSet.class)

.publisherOracle(oracleRow -> {

try {

return new Employee(

oracleRow.getObject("id", Long.class),

oracleRow.getObject("first_name", String.class),

oracleRow.getObject("last_name", String.class));

}

catch (SQLException getObjectException) {

// Unchecked exceptions thrown by a row mapping function

will be

// emitted to each Subscriber's onError method.

throw new RuntimeException(getObjectException);

}

});

employeePublisher.subscribe(

// This subscriber will close the ResultSet's Statement

new Flow.Subscriber<Employee>() {

public void onSubscribe(Flow.Subscription subscription) {

subscription.request(Long.MAX_VALUE);

}

public void onNext(Employee item) { }

public void onError(Throwable throwable) { closeStatement(); }

public void onComplete() { closeStatement(); }

void closeStatement() {

try { resultSetStatement.close(); }

catch (SQLException closeException) { log(closeException); }

}

});

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22-8

return employeePublisher;

}

Instances of

OracleRow

, which the mapping function receives as input, becomes invalid after

the function returns. Restricting the access of

OracleRow

to the scope of the mapping function

enables the driver to efficiently manage the memory that is used to store row data. If you

need a persistent copy of an

OracleRow

, then you can use the

OracleRow.clone

method to

create a new instance of

OracleRow

, which is backed by a copy of the original

OracleRow

data. The

OracleRow

returned by the

clone

method remains valid outside the scope of the

mapping function and retains its data even after the database connection is closed.

The row mapping function must return a non-null value or throw an unchecked exception. If

the mapping function throws an unchecked exception, then it is delivered to row data

subscribers as an

onError

signal. The row data Publisher supports multiple Subscribers.

Row data emission to multiple Subscribers follow certain policies as stated below:

• A Subscriber will not receive an

onNext

signal for row data emitted before the Subscriber

received an

onSubscribe

signal.

• A Subscriber will not receive an

onNext

signal until demand has been signaled by all

other Subscribers.

The following table demonstrates the event flow while working with multiple subscribers:

Table 22-2 Emission to Multiple Subscribers

Time Event Cause

0 SubscriberA receives an

onSubscribe

signal

A call to the row data Publisher’s

subscribe (Subscriber) method

requested a Subscription for

SubscriberA

1 SubscriberA requests 1 row SubscriberA signaled demand on

its Subscription

2 SubscriberA receives data for the

first row of the ResultSets

The row data Publisher fetched a

row of data that was requested

by SubscriberA

3 SubscriberB receives an

onSubscribe

signal

A call to the row data Publisher’s

subscribe (Subscriber) method

requested a Subscription for

SubscriberB

4 SubscriberA requests 1 row SubscriberA signaled demand on

its Subscription

5 SubscriberB requests 1 row SubscriberB signaled demand on

its Subscription

6 Both SubscriberA and

SubscriberB receive data for the

second row of the ResultSet

The row data Publisher fetched a

row of data that was requested

by both Subscribers

7 SubscriberA requests 1 row SubscriberA signaled demand on

its Subscription

8 No row data is emitted The row data Publisher does not

emit the next row until

ALL

subscribers have requested it.

9 SubscriberB requests 1 row SubscriberB signaled demand on

its Subscription

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Table 22-2 (Cont.) Emission to Multiple Subscribers

Time Event Cause

10 Both SubscriberA and

SubscriberB receive data for the

third row of the ResultSet

The row data Publisher fetched a

row of data that was requested

by both Subscribers

Note:

SubscriberB never received data for the first row. This is because

SubscriberB subscribed after the first row was emitted. Also, no data was

emitted at 8 seconds. This is because all Subscribers need to request the

next row before it is emitted. At 8 seconds, SubscriberA had requested for

the next row, but SubscriberB had not placed a request till then.

22.2.4 Reading LOB Data Using Asynchronous Methods

The

OracleBlob

OracleBFile

OracleClob

, and

OracleNClob

interfaces expose a

publisherOracle(long)

method for asynchronous reading of LOB data.

The argument to the

publisherOracle(long)

method is a position of the LOB from

where the data is read. The

OracleBlob.publisherOracle(long)

and

OracleBFile.publisherOracle(long)

methods return a Publisher<byte[]> type. This

Publisher emits segments of binary data that have been read from the LOB. The

OracleClob.publisherOracle(long)

and

OracleNClob.publisherOracle(long)

methods return a Publisher<String> type. This Publisher emits segments of character

data that have been read from the LOB.

The following example demonstrates how to asynchronously read binary data from a

LOB.

/**

* Asynchronously reads binary data from a BLOB

* @param connection Connection to a database where the BLOB resides

* @param employeeId ID associated to the BLOB

* @return A Publisher that emits binary data of a BLOB

* @throws SQLException If a database access error occurs before the

* BLOB can be read

Flow.Publisher<byte[]> readLOB(Connection connection, long

employeeId)

throws SQLException {

PreparedStatement lobQueryStatement = connection.prepareStatement(

"SELECT photo_bytes FROM employee_photos WHERE id = ?");

lobQueryStatement.setLong(1, employeeId);

ResultSet resultSet = lobQueryStatement.executeQuery();

if (!resultSet.next())

throw new SQLException("No photo found for employee ID " +

employeeId);

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OracleBlob photoBlob =

(OracleBlob)resultSet.unwrap(OracleResultSet.class).getBlob(1);

Flow.Publisher<byte[]> photoPublisher = photoBlob.publisherOracle(1);

photoPublisher.subscribe(

// This subscriber will close the PreparedStatement and BLOB

new Flow.Subscriber<byte[]>() {

public void onSubscribe(Flow.Subscription subscription) {

subscription.request(Long.MAX_VALUE);

}

public void onNext(byte[] item) { }

public void onError(Throwable throwable) { freeResources(); }

public void onComplete() { freeResources(); }

void freeResources() {

try { lobQueryStatement.close(); }

catch (SQLException closeException) { log(closeException); }

try { photoBlob.free(); }

catch (SQLException freeException) { log(freeException); }

}

});

return photoPublisher;

}

You cannot configure the size of data segments emitted by the LOB publishers. The driver

chooses a segment size that is optimized as per the

DB_BLOCK_SIZE

parameter of the

database.

22.2.5 Writing LOB Data Using Asynchronous Methods

The

OracleBlob

OracleClob

, and

OracleNClob

interfaces expose a

subscriberOracle(long)

method for asynchronous writing of LOB data.

The argument to the

subscriberOracle(long)

method is a position of the LOB where the

data is written. The

OracleBlob.subscriberOracle(long)

method returns a

Subscriber<byte[]>

type. This Subscriber receives segments of binary data that are written

to the LOB. The

OracleClob.subscriberOracle(long)

method and the

OracleNClob.subscriberOracle(long)

method return a

Subscriber<String>

type. These

Subscribers receive segments of character data that are written to the LOB.

The following examples demonstrate how to asynchronously write binary data to a LOB.

/**

* Asynchronously writes binary data to a BLOB

* @param connection Connection to a database where the BLOB resides

* @param bytesPublisher Publisher that emits binary data

* @return A CompletionStage that completes with a reference to the BLOB,

* after all binary data is written.

* @throws SQLException If a database access error occurs before the table

data is

* fetched

CompletionStage<Blob> writeLOB(

Connection connection, Flow.Publisher<byte[]> bytesPublisher)

throws SQLException {

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OracleBlob oracleBlob =

(OracleBlob)

connection.unwrap(OracleConnection.class).createBlob();

// This future is completed after all bytes have been written to

the BLOB

CompletableFuture<Blob> writeFuture = new CompletableFuture<>();

Flow.Subscriber<byte[]> blobSubscriber =

oracleBlob.subscriberOracle(1L,

// This Subscriber will receive a terminal signal when all

byte[]'s

// have been written to the BLOB.

new Flow.Subscriber<Long>() {

long totalWriteLength = 0;

@Override

public void onSubscribe(Flow.Subscription subscription) {

subscription.request(Long.MAX_VALUE);

}

@Override

public void onNext(Long writeLength) {

totalWriteLength += writeLength;

log(totalWriteLength + " bytes written.");

}

@Override

public void onError(Throwable throwable) {

writeFuture.completeExceptionally(throwable);

}

@Override

public void onComplete() {

writeFuture.complete(oracleBlob);

}

});

bytesPublisher.subscribe(blobSubscriber);

return writeFuture;

}

The

OracleBlob

OracleClob

, and

OracleNClob

interfaces also expose a

subscriberOracle(long, Subscriber<Long>)

method that performs the same

function as the single-argument form of the

subscriberOracle(long)

method.

However, the single-argument form also accepts a

Subscriber<Long>

type. The

Subscriber<Long>

type notifies a Subscriber to receive the result of write operations

against the database. Each time an asynchronous write operation completes, the

Subscriber<Long>

type receives an

onNext

signal with the number of bytes or number

of characters written by the operation. If an asynchronous write operation fails, the

Subscriber<Long>

type receives an

onError

signal. After the final write operation

completes, the

Subscriber<Long>

receives an

onComplete

signal.

After the

CompletionStage<Blob>

returned by the

writeLOB

method completes, the

resulting Blob object can be passed to the

insertLOB

method to have the BLOB data

stored in a table.

Chapter 22

About Building an Application with Reactive Extensions

22-12

The following examples demonstrate how to insert the data.

/**

* Asynchronously inserts BLOB data into a table by executing a DML SQL

* statement

* @param connection Connection to a database where the table data resides

* @param employeeId ID related to the BLOB data

* @param photoBlob Reference to BLOB data

* @return A Publisher that emits the number of rows inserted (always 1)

* @throws SQLException If a database access error occurs before the DML

* SQL can be executed

Flow.Publisher<Long> insertLOB(

Connection connection, long employeeId, Blob photoBlob)

throws SQLException {

PreparedStatement lobInsertStatement = connection.prepareStatement(

"INSERT INTO employee_photos(id, photo_bytes) VALUES (? ,?)");

lobInsertStatement.setLong(1, employeeId);

lobInsertStatement.setBlob(2, photoBlob);

Flow.Publisher<Long> insertPublisher =

lobInsertStatement.unwrap(OraclePreparedStatement.class)

.executeUpdateAsyncOracle();

insertPublisher.subscribe(new Flow.Subscriber<Long>() {

@Override

public void onSubscribe(Flow.Subscription subscription) {

subscription.request(1L);

}

@Override

public void onNext(Long item) { }

@Override

public void onError(Throwable throwable) { releaseResources(); }

@Override

public void onComplete() { releaseResources(); }

void releaseResources() {

try { lobInsertStatement.close(); }

catch (SQLException closeException) { log(closeException); }

try { photoBlob.free(); }

catch (SQLException freeException) { log(freeException); }

}

});

return insertPublisher;

}

22.2.6 Committing a Transaction Using Asynchronous Methods

The

OracleConnection

interface exposes the

commitAsyncOracle

and

rollbackAsyncOracle

methods for asynchronous transaction completion.

Both the

commitAsyncOracle

and

rollbackAsyncOracle

methods return a

Flow.Publisher<Void>

type. The Publishers do not emit any item, as signified by their

Chapter 22

About Building an Application with Reactive Extensions

22-13

<Void>

type. The Publishers emit a single

onComplete

onError

signal to indicate

whether the commit or rollback operation was completed successfully or not.

The following example demonstrates how to asynchronously commit a transaction.

/**

* Asynchronously commits a transaction

* @param connection Connection to a database with an active

transaction

* @return A Publisher that emits a terminal signal when the

transaction

* has been committed

* @throws SQLException If a database access error occurs before the

* transaction can be committed

public Flow.Publisher<Void> commitTransaction(Connection connection)

throws SQLException {

return connection.unwrap(OracleConnection.class)

.commitAsyncOracle();

}

The

commitAsyncOracle

and

rollbackAsyncOracle

methods perform the same

function as the

Connection.commit

and

Connection.rollback

methods.

22.2.7 Closing a Connection Using Asynchronous Methods

The

OracleConnection

interface exposes the

closeAsyncOracle

method for closing

an asynchronous connection.

The

closeAsyncOracle

method returns a

Flow.Publisher<Void>

type. The Publisher

does not emit any item, as signified by its

<Void>

type. The Publisher emits a single

onComplete

onError

signal to indicate whether the connection was closed

successfully or not.

The following example demonstrates how to asynchronously close a connection.

/**

* Asynchronously closes a connection

* @param connection Connection to be closed

* @return A Publisher that emits a terminal signal when the

connection

* has been closed

* @throws SQLException If a database access error occurs before the

* connection can be closed

Flow.Publisher<Void> closeConnection(Connection connection)

throws SQLException {

return connection.unwrap(OracleConnection.class)

.closeAsyncOracle();

}

The

closeAsyncOracle

method performs the same function as the

Connection.close

method.

Chapter 22

About Building an Application with Reactive Extensions

22-14

22.3 Threading Model of Asynchronous Methods

This section describes the threading model of asynchronous methods.

When an asynchronous method is called, it performs as much work as possible on the calling

thread, without blocking on a network read. An asynchronous method call returns

immediately after a request is written to the network, without waiting for a response. If the

write buffer of the operating system is not large enough to store a complete request, then the

calling thread may become blocked until this buffer is flushed.

Once the write job is complete, the network channel is registered for I/O readiness polling. A

single thread polls the network channels of all Oracle JDBC Connections in the same JVM.

The I/O polling thread is named

oracle.net.nt.TcpMultiplexer

, and is configured as a

daemon thread. This polling thread performs a blocking operation using a Selector.

When I/O readiness is detected for a network channel, the polling thread arranges for a

worker thread to handle the event. The worker thread reads from the network and then

notifies a Publisher that an operation is complete. Upon notification, the Publisher arranges

worker threads that emit a signal to each of its Subscribers.

The

java.util.concurrent.Executor

interface manages the worker threads. The default

Executor is the

java.util.concurrent.ForkJoinPool.commonPool

method. You can call the

OracleConnectionBuilder.executorOracle(Executor)

method to specify an alternative

Executor.

22.4 About the Flow API

The

java.util.concurrent.Flow

types define the minimal set of operations that you can use

to create a reactive stream.

You can write application code directly against the Flow API. However, you must implement

the low-level signal processing in accordance with the reactive-streams specification as

specified in the following link

https://github.com/reactive-streams/reactive-streams-jvm/blob/master/README.md

The JDBC Reactive Extensions APIs handle the low-level mechanics of the Flow API to the

application using

java.util.concurrent.Flow.Publisher

and

java.util.concurrent.Flow.Subscriber

. Popular libraries such as Reactor, RxJava, and

Akka-Streams interface with the

org.reactivestreams.Publisher

and

org.reactivestreams.Subscriber

types defined by the

reactive-streams-jvm

project as

specified in the following link:

https://github.com/reactive-streams/reactive-streams-jvm/tree/master/api/src/main/java/org/

reactivestreams

Although the

org.reactivestreams.Publisher

type and the

org.reactivestreams.Subscriber

type, and their

java.util.concurrent.Flow

counterparts

declare the same interface, the Java compiler must still consider them to be distinct types.

You can convert between the Flow type and the

org.reactivestreams

type using the

org.reactivestreams.FlowAdapters

class as specified in the following link

https://github.com/reactive-streams/reactive-streams-jvm/tree/master/api/src/main/java9/org/

reactivestreams

Chapter 22

Threading Model of Asynchronous Methods

22-15

Oracle recommends that you use the reactive streams libraries when interfacing with

the Flow types exposed by the JDBC driver.

22.5 Using the FlowAdapters Class

The libraries covered in this section interfaces with the

org.reactivestreams

types

described in the About the Flow API section.

The following code snippet shows how the

FlowAdapters

class can convert the

Flow.Publisher

types into the

org.reactivestreams

types.

Example 22-1 Conversion to org.reactivestreams Types

public static org.reactivestreams.Publisher<ResultSet> publishQuery(

PreparedStatement queryStatement) {

try {

Flow.Publisher<OracleResultSet> queryPublisher =

queryStatement.unwrap(OraclePreparedStatement.class)

.executeQueryAsyncOracle();

return FlowAdapters.toPublisher(queryPublisher);

}

catch (SQLException sqlException) {

return createErrorPublisher(sqlException);

}

public static <T> org.reactivestreams.Publisher<T> publishRows(

ResultSet resultSet, Function<OracleRow, T> rowMappingFunction) {

try {

Flow.Publisher<T> rowPublisher =

resultSet.unwrap(OracleResultSet.class)

.publisherOracle(rowMappingFunction);

return FlowAdapters.toPublisher(rowPublisher);

}

catch (SQLException sqlException) {

return createErrorPublisher(sqlException);

}

22.6 Streaming Row Data with the Reactor Library

The Reactor library defines a Flux type that represents a stream of many items and a

Mono type that represents a stream of just one item.

The following example shows how to create a Flux of row data using the Reactive

Extensions.

private Publisher<Employee> queryAllEmployees(Connection

connection) {

return Flux.using(

Chapter 22

Using the FlowAdapters Class

22-16

// Prepare a SQL statement.

() -> connection.prepareStatement("SELECT * FROM emp"),

// Execute the PreparedStatement.

preparedStatement ->

// Create a Mono which emits one ResultSet.

Mono.from(publishQuery(preparedStatement))

// Flat map the ResultSet to a Flux which emits many Rows. Each

row

// is mapped to an Employee object.

.flatMapMany(resultSet ->

publishRows(resultSet, row -> mapRowToEmployee(row))),

// Close the PreparedStatement after emitting the last Employee

object

prepareStatement -> {

try {

prepareStatement.close();

}

catch (SQLException sqlException) {

throw new RuntimeException(sqlException);

}

});

}

The

using

factory method creates a Flux that depends on a resource that must be released

explicitly. In this case, the resource is a

PreparedStatement

instance that is released by

calling the

method.

The first lambda argument creates the

PreparedStatement

instance. This lambda is executed

before the Flux begins to emit items.

The second lambda argument uses the

PreparedStatement

instance to create a stream of

row data that is mapped to an Employee object. First, the

PreparedStatement

instance is

executed by the call to the

publishQuery

method. As the query execution Publisher emits a

Chapter 22

Streaming Row Data with the Reactor Library

22-17

single

ResultSet

, it is adapted into a Mono. Once the query execution completes, the

Mono emits the

ResultSet

into the lambda specified by the

flatMapMany

method. This

lambda calls the

publishRows

method with a function to map

OracleRow

objects into

the Employee objects. This results in the

flatMapMany

method call returning a

Flux

Employee objects, where each Employee is mapped from a row of the

ResultSet

object.

The third lambda argument closes the

PreparedStatement

instance. This lambda is

executed after the Flux emits its last item.

22.7 Streaming Row Data with the RxJava Library

The RxJava library defines a Flowable type that represents a stream of many items,

and a Single type that represents a stream of just one item.

The following example shows how to create a Flowable of row data using the Reactive

Extensions.

private Publisher<Employee> queryAllEmployees(Connection

connection) {

return Flowable.using(

// Prepare a SQL statement

() -> connection.prepareStatement("SELECT * FROM emp"),

// Execute the PreparedStatement

queryStatement ->

// Create a Single which emits one ResultSet

Single.fromPublisher(publishQuery(queryStatement))

// Flat map the ResultSet to a Flowable which emits many

rows, where

// each row is mapped to an Employee object

.flatMapPublisher(resultSet ->

publishRows(resultSet, oracleRow ->

mapRowToEmployee(oracleRow))),

// Close the PreparedStatement after emitting the last

Employee object

PreparedStatement::close

);

Chapter 22

Streaming Row Data with the RxJava Library

22-18

}

The

using

factory method creates a Flowable that depends on a resource that must be

released explicitly. In this case, the resource is a

PreparedStatement

instance that is

released by calling the

method.

The first lambda argument creates the

PreparedStatement

instance. This lambda is executed

before the Flowable begins to emit items.

The second lambda argument uses the

PreparedStatement

instance to create a stream of

row data that is mapped to an Employee object. First, the

PreparedStatement

instance is

executed by the

publishQuery

method call. As the query execution Publisher emits a single

ResultSet

object, it is adapted into a Single. Once the query execution completes, the Single

emits the

ResultSet

object into the lambda specified by the

flatMapPublisher

method. This

lambda calls the

publishRows

method with a function to map

OracleRow

objects into

Employee objects. This results in the

flatMapPublisher

method call returning a Flowable of

Employee objects, where each Employee is mapped from a row of the

ResultSet

The third method handle argument closes the

PreparedStatement

instance. This lambda is

executed after the Flowable emits its last item.

22.8 Streaming Row Data with the Akka Streams Library

The Akka Streams library defines a Source type that represents a stream of items.

The following example shows how to create a Source of row data using the Reactive

Extensions.

private Source<Employee, NotUsed> queryAllEmployees(Connection

connection) {

final PreparedStatement queryStatement;

try {

queryStatement = connection.prepareStatement("SELECT * FROM emp");

}

catch (SQLException prepareStatementFailure) {

return Source.failed(prepareStatementFailure);

}

// Create a Source which emits one ResultSet

return Source.fromPublisher(publishQuery(queryStatement))

// Flat map the ResultSet to a Source which emits many Rows, where

each

Chapter 22

Streaming Row Data with the Akka Streams Library

22-19

// Row is mapped to an Employee object

.flatMapConcat(resultSet -> {

Publisher<Employee> employeePublisher =

publishRows(resultSet, oracleRow ->

mapRowToEmployee(oracleRow));

return Source.fromPublisher(employeePublisher);

})

// This Sink closes the PreparedStatement when the Source

terminates

.alsoTo(Sink.onComplete(result -> queryStatement.close()));

}

PreparedStatement

instance is used to create a stream of row data that is mapped

to an Employee object. First, the

PreparedStatement

instance is executed by the

publishQuery

method call. The query execution Publisher emits a single

ResultSet

object. This Publisher is adapted into a Source. Once the query completes, the Source

emits the

ResultSet

object into the lambda specified by the

flatMapConcat

method.

This lambda calls the

publishRows

method with a function to map

OracleRow

objects

into Employee objects. This results in the

flatMapConcat

method call returning a

Source of Employee objects, where each Employee is mapped from a row of the

ResultSet

object.

The

PreparedStatement

instance is a resource that needs to be explicitly closed. This

is handled by the

alsoTo

method call that specifies a Sink that closes the

PreparedStatement

instance when the Source emits an

onComplete

onError

signal.

22.9 Limitations of JDBC Reactive Extensions

This section describes the limitations of JDBC Reactive Extensions.

JDBC Reactive Extensions have the following limitations:

• A Connection does not accept more than one asynchronous operation at a time.

An asynchronous method call blocks the calling thread if there is another operation

that is currently in progress.

• You must access the asynchronous methods through the

java.sql.Wrapper.unwrap

method, instead of accessing those through a type

cast. This ensures correct behavior of the asynchronous methods when you use

them with proxy Oracle JDBC classes, for example, when you use asynchronous

methods with connection pools.

• Reading large responses from the network may require blocking I/O bound

operations. Blocking read operations can occur if the driver reads a response that

is larger than the TCP Receive buffer size.

Chapter 22

Limitations of JDBC Reactive Extensions

22-20

• Asynchronous SQL execution supports neither scrollable

ResultSet

types nor sensitive

ResultSet

types.

Chapter 22

Limitations of JDBC Reactive Extensions

22-21

Support for Java library for Reactive Streams

Ingestion

Oracle Database Release 21c introduces a Java library that provides support for Reactive

Streams Ingestion (RSI), which enables customers to efficiently stream data into Oracle

Database. The new Java library enables Java applications to continuously receive and

ingest data from a large group of clients.

Using the direct path load method of Oracle Database for inserting data, the new Java library

makes the ingestion process nonblocking and extremely fast. It uses an extension of the

existing UCP APIs, which enables the ingestion process to furnish several high-availability

and scalability features of the database, like support for table partitions, Oracle RAC

connection affinity, and sharding.

23.1 Overview of the Java Library for Reactive Streams

Ingestion

The Java library for Reactive Streams Ingestion (RSI) enables efficient data streaming into

Oracle Database in a nonblocking way.

This library is particularly useful when a large number of clients use the database to persist

information in the form of table rows, and do not want to be blocked waiting for a

synchronous response from the database. So, in case of use cases like the following, when

the application must ingest streaming data into the database at a very high speed, and

persist it in the form of rows in an Oracle Database table, you can use this library:

• Internet of Things (IoT) sensors

• Time series data for stock trade

• Call detail records (CDRs)

• Geospatial activities

• Video web sites

• Social media posts

For using this library, you must add the following

JAR

files to your

CLASSPATH

•

rsi.jar

•

ojdbc11.jar

•

ucp.jar

•

ons.jar

23-1

23.2 Features of the Java Library for Reactive Streams

Ingestion

The Java library for Reactive Streams Ingestion (RSI) uses the direct path load

method of Oracle Database for inserting data. It also uses Oracle Universal

Connection Pool (UCP) to furnish several high-availability and scalability features of

the Database, such as support for table partitions, Oracle RAC connection affinity, and

sharding. So, this library provides the benefits of the following features:

• Reactive Streams Ingestion

• Direct Path Load

• Universal Connection Pool

23.2.1 Reactive Streams Ingestion

This is the core feature of the Java library for Reactive Streams Ingestion, which

provides the APIs to handle the logic.

The library implements the

Java.util.concurrent.Flow

Subscriber interface. You

must implement the

Java.util.concurrent.Flow

Publisher interface for invoking the

methods of the Subscriber interface. The Subscriber interface has the following

methods:

•

onSubscribe

Invoke this method only once for establishing the initial relationship between the

Subscriber interface and the Publisher interface.

•

onNext

Invoke this method for creating each new row in the implementation of the

Subscriber interface that the library provides.

•

onError

Invoke this method in case of any error that might occur during the ingestion

process.

•

onComplete

Invoke this method when the ingestion job completes.

The Subscriber interface calls the

request(n)

method or the

cancel

method of the

Java.util.concurrent.Flow

Subscriber interface to indicate whether it can accept

more data or it should stop ingesting data.

See Also:

The Java.util.concurrent.Flow Subscriber Interface

23.2.2 Direct Path Load

The Java library for Reactive Streams Ingestion uses the direct path load method of

Oracle Database for nonblocking data ingestion. This method eliminates the SQL layer

Chapter 23

Features of the Java Library for Reactive Streams Ingestion

23-2

overhead significantly as it formats Oracle data blocks and writes the data blocks directly to

the database files.

See Also:

The Direct Path Load Method

During the direct path load method call, the database appends the inserted data after the

existing data in the table. This method writes data directly into data files, bypassing the buffer

cache. It does not perform reuse of free space in the table, and ignores the referential

integrity constraints. So, a direct path load method can perform significantly better than

conventional insert operations.

23.2.3 Universal Connection Pool

The Java library for Reactive Streams Ingestion (RSI) uses Universal Connection Pool (UCP)

for various connection pooling and management activities like sharding topology knowledge,

Fast Application Notification (FAN) awareness for an Oracle Real Application Cluster (Oracle

RAC) database, and so on.

The RSI library uses the UCP sharding APIs to establish a proper connection for the

specified sharding key. You can map each record in RSI to a unique chunk ID and then use

the unique chunk ID to group these records together. When the RSI library has enough

records to send to the database, then it borrows a chunk specific connection from UCP and

uses that connection to insert the record into the sharded database.

23.3 Code Samples: Java Library for Reactive Streams

Ingestion

This section contains code samples showing how to use the Reactive Streams Ingestion

library.

• PushPublisher

• Flow.Publisher Dynamic Implementations

• Flow.Publisher Third-Party implementations

23.3.1 PushPublisher

This is the simplest way to use the Reactive Streams Ingestion (RSI) library, where the RSI

library implements the

java.util.concurrent.Flow.Subscriber

interface and the Java code

in your application implements the

java.util.concurrent.Flow.Publisher

interface.

The following example demonstrates this implementation, where you create a Publisher and

the RSI library subscribes to that Publisher:

Example 23-1 PushPublisher

package oracle.rsi.demos;

import java.sql.SQLException;

import java.time.Duration;

Chapter 23

Code Samples: Java Library for Reactive Streams Ingestion

23-3

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import oracle.rsi.ReactiveStreamsIngestion;

import oracle.rsi.PushPublisher;

public class SimplePushPublisher {

public static void main(String[] args) throws SQLException {

ExecutorService workerThreadPool = Executors.newFixedThreadPool(2);

ReactiveStreamsIngestion rsi = ReactiveStreamsIngestion

.builder()

.url(

"jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)

(HOST=example.com)(PORT=5521))

(CONNECT_DATA=(SERVICE_NAME=myservice.com)))")

.username(<user_name>)

.password(<password>)

.schema(<schema_name>)

.executor(workerThreadPool)

.bufferRows(10)

.bufferInterval(Duration.ofSeconds(20))

.table("customers")

.columns(new String[] { "id", "name", "region" })

.build();

PushPublisher<Object[]> pushPublisher =

ReactiveStreamsIngestion.pushPublisher();

pushPublisher.subscribe(rsi.subscriber());

//Ingests byte arrays using the accept method

pushPublisher.accept(new Object[] { 1, "John Doe", "North" });

pushPublisher.accept(new Object[] { 2, "Jane Doe", "North" });

pushPublisher.accept(new Object[] { 3, "John Smith", "South" });

try {

pushPublisher.close();

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

rsi.close();

workerThreadPool.shutdown();

}

Chapter 23

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23-4

23.3.2 Flow.Publisher Dynamic Implementations

The following example shows how to use the RSI library when your application implements

the Flow.Publisher interface and subscribes to the library.

Example 23-2 Flow.Publisher Dynamic Implementations

package oracle.rsi.demos;

import java.sql.SQLException;

import java.time.Duration;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.Flow.Publisher;

import java.util.concurrent.Flow.Subscriber;

import java.util.concurrent.Flow.Subscription;

import java.util.function.Consumer;

import oracle.rsi.ReactiveStreamsIngestion;

public class SimpleFlowPublisher {

public static void main(String[] args) throws SQLException {

ExecutorService workerThreadPool = Executors.newFixedThreadPool(2);

ReactiveStreamsIngestion rsi = ReactiveStreamsIngestion

.builder()

.url(

"jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)

(HOST=example.com)(PORT=5521))(CONNECT_DATA=(SERVICE_NAME=myservice.com)))")

.username(<user_name>)

.password(<password>)

.schema(<schema_name>)

.executor(workerThreadPool)

.bufferRows(1)

.bufferInterval(Duration.ofMinutes(60))

.table("customers")

.columns(new String[] { "id", "name", "region" })

.build();

SimpleObjectPublisher<Object[]> publisher = new

SimpleObjectPublisher<Object[]>();

publisher.subscribe(rsi.subscriber());

SimpleObjectPublisher<Object[]> anotherPublisher = new

SimpleObjectPublisher<Object[]>();

anotherPublisher.subscribe(rsi.subscriber());

publisher.accept(new Object[] { 1, "John Doe", "North" });

publisher.accept(new Object[] { 2, "Jane Doe", "North" });

publisher.accept(new Object[] { 3, "John Smith", "South" });

anotherPublisher.accept(new Object[] { 4, "John Doe", "North" });

anotherPublisher.accept(new Object[] { 5, "Jane Doe", "North" });

Chapter 23

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23-5

anotherPublisher.accept(new Object[] { 6, "John Smith", "South" });

rsi.close();

workerThreadPool.shutdown();

}

class SimpleObjectPublisher<T> implements Publisher<T>, Consumer<T> {

Subscriber<? super T> subscriber;

Subscription subscription = new SimpleObjectSubscription();

//Data streaming starts

@Override

public void subscribe(Subscriber<? super T> subscriber) {

this.subscriber = subscriber;

this.subscriber.onSubscribe(subscription);

}

@Override

public void accept(T t) {

subscriber.onNext(t);

}

// You must provide this subscription

class SimpleObjectSubscription implements Subscription {

@Override

public void request(long n) {

System.out.println("Library requesting: " + n + " records");

}

@Override

public void cancel() {

// TODO Auto-generated method stub

}

23.3.3 Flow.Publisher Third-Party implementations

The following example shows how to use the RSI library when a third-party

implements the Flow.Publisher interface.

In the following example, the standard JDK

SubmissionPublisher

interface is the

third-party interface.

Chapter 23

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23-6

Example 23-3 Flow.Publisher Third-Party Implementations

package oracle.rsi.demos;

import java.sql.SQLException;

import java.time.Duration;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.SubmissionPublisher;

import oracle.rsi.ReactiveStreamsIngestion;

public class SimpleSubmissionPublisher {

public static void main(String[] args) throws SQLException {

ExecutorService workerThreadPool = Executors.newFixedThreadPool(2);

ReactiveStreamsIngestion rsi = ReactiveStreamsIngestion

.builder()

.url(

"jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)

(HOST=example.com)(PORT=5521))(CONNECT_DATA=(SERVICE_NAME=myservice.com)))")

.username(<user_name>)

.password(<password>)

.schema(<schema_name>)

.executor(workerThreadPool)

.bufferRows(10)

.bufferInterval(Duration.ofSeconds(20))

.table("customers")

.columns(new String[] { "id", "name", "region" })

.build();

SubmissionPublisher<Object[]> publisher = new SubmissionPublisher<>();

publisher.subscribe(rsi.subscriber());

publisher.submit(new Object[] { 1, "John Doe", "North" });

publisher.submit(new Object[] { 2, "Jane Doe", "North" });

publisher.submit(new Object[] { 3, "John Smith", "South" });

while (publisher.estimateMaximumLag() > 0);

try {

publisher.close();

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

rsi.close();

workerThreadPool.shutdown();

}

Chapter 23

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23-7

}

23.4 Limitations of Java library for Reactive Streams

Ingestion

Reactive streams ingestion of data streams may not ingest all the data into the

database in case of unexpected crashes or errors because the library may lose some

of the records while trying to store them in the database.

Apart from the possibility of data loss due to database crashes, this library has the

following limitations:

• It does not support database triggers.

• It does not check referential integrity.

• It does not support clustered tables.

• It does not support loading of remote objects.

• It does not support loading of

VARRAY

columns.

• It does not support

LONG

data type with streams.

• It expects the

LONG

data type to be the last column in the database table.

• It expects all partitioning columns to appear before any column with

LOB

data type.

Chapter 23

Limitations of Java library for Reactive Streams Ingestion

23-8

OCI Connection Pooling

The Java Database Connectivity (JDBC) Oracle Call Interface (OCI) driver connection

pooling functionality is part of the JDBC client. This functionality is provided by the

OracleOCIConnectionPool

class.

A JDBC application can have multiple pools at the same time. Multiple pools can correspond

to multiple application servers or pools to different data sources. The connection pooling

provided by the JDBC OCI driver enables applications to have multiple logical connections,

all using a small set of physical connections. Each call on a logical connection gets routed on

to the physical connection that is available at the time of call.

This chapter contains the following sections:

• Background of OCI Driver Connection Pooling

• Comparison Between OCI Driver Connection Pooling and Shared Servers

• About Defining an OCI Connection Pool

• About Connecting to an OCI Connection Pool

• Sample Code for OCI Connection Pooling

• Statement Handling and Caching

• JNDI and the OCI Connection Pool

Note:

Use OCI connection pooling if you need session multiplexing. Otherwise, Oracle

recommends using Universal Connection Pool.

24.1 Background of OCI Driver Connection Pooling

The Oracle JDBC OCI driver provides several transaction monitor capabilities, such as the

fine-grained management of Oracle sessions and connections. It is possible for a high-end

application server or transaction monitor to multiplex several sessions over fewer physical

connections on a call-level basis, thereby achieving a high degree of scalability by pooling of

connections and back-end Oracle server processes.

The connection pooling provided by the

OracleOCIConnectionPool

interface simplifies the

session/connection separation interface hiding the management of the physical connection

pool. The Oracle sessions are the

OracleOCIConnection

objects obtained from

OracleOCIConnectionPool

. The connection pool itself is usually configured with a much

smaller shared pool of physical connections, translating to a back-end server pool containing

an identical number of dedicated server processes. Note that many more Oracle sessions

can be multiplexed over this pool of fewer shared connections and back-end Oracle

processes.

24-1

24.2 Comparison Between OCI Driver Connection Pooling

and Shared Servers

In some ways, what OCI driver connection pooling offers on the middle tier is similar to

what shared server processes offer on the back end. OCI driver connection pooling

makes a dedicated server instance behaves as a shared instance by managing the

session multiplexing logic on the middle tier. Therefore, the pooling of dedicated server

processes and incoming connections into the dedicated server processes is controlled

by the OCI connection pool on the middle tier.

The main difference between OCI connection pooling and shared servers is that in the

case of shared servers, the connection from the client is typically to a dispatcher in the

database instance. The dispatcher is responsible for directing the client request to an

appropriate shared server. On the other hand, the physical connection from the OCI

connection pool is established directly from the middle tier to the Oracle dedicated

server process in the back-end server pool.

Note that OCI connection pool is mainly beneficial only if the middle tier is

multithreaded. Each thread could maintain a session to the database. The actual

connections to the database are maintained by

OracleOCIConnectionPool

, and these

connections, including the pool of dedicated database server processes, are shared

among all the threads in the middle tier.

24.3 About Defining an OCI Connection Pool

This section describes the following concepts:

• Overview of Creating an OCI Connection Pool

• Importing the oracle.jdbc.pool and oracle.jdbc.oci Packages

• Creating an OCI Connection Pool

• Setting the OCI Connection Pool Parameters

• Checking the OCI Connection Pool Status

24.3.1 Overview of Creating an OCI Connection Pool

An OCI connection pool is created at the beginning of the application. Creating

connections from a pool is quite similar to creating connections using the

OracleDataSource

class.

The

oracle.jdbc.pool.OracleOCIConnectionPool

class, which extends the

OracleDataSource

class, is used to create OCI connection pools. From an

OracleOCIConnectionPool

instance, you can obtain logical connection objects. These

connection objects are of the

OracleOCIConnection

class type. This class implements

the

OracleConnection

interface. The

Statement

objects you create from the

OracleOCIConnection

instance have the same fields and methods as

OracleStatement

objects you create from

OracleConnection

instances.

The following code shows header information for the

OracleOCIConnectionPool

class:

* @param us ConnectionPool user-id.

Chapter 24

Comparison Between OCI Driver Connection Pooling and Shared Servers

24-2

* @param p ConnectionPool password

* @param name logical name of the pool. This needs to be one in the

* tnsnames.ora configuration file.

@param config (optional) Properties of the pool, if the default does not

suffice. Default connection configuration is min =1, max=1,

incr=0

Please refer setPoolConfig for property names.

Since this is optional, pass null if the default configuration

suffices.

* @return

* Notes: Choose a userid and password that can act as proxy for the users

* in the getProxyConnection() method.

If config is null, then the following default values will take

effect

CONNPOOL_MIN_LIMIT = 1

CONNPOOL_MAX_LIMIT = 1

CONNPOOL_INCREMENT = 0

public synchronized OracleOCIConnectionPool

(String user, String password, String name, Properties config)

throws SQLException

* This will use the user-id, password and connection pool name values set

LATER using the methods setUser, setPassword, setConnectionPoolName.

* @return

* Notes:

No OracleOCIConnection objects can be created on

this class unless the methods setUser, setPassword, setPoolConfig

are invoked.

When invoking the setUser, setPassword later, choose a userid and

password that can act as proxy for the users

* in the getProxyConnection() method.

public synchronized OracleOCIConnectionPool ()

throws SQLException

24.3.2 Importing the oracle.jdbc.pool and oracle.jdbc.oci Packages

Before you create an OCI connection pool, import the following to have Oracle OCI

connection pooling functionality:

import oracle.jdbc.pool.*;

import oracle.jdbc.oci.*;

24.3.3 Creating an OCI Connection Pool

The following code show how you create an instance of the

OracleOCIConnectionPool

class

called

cpool

Chapter 24

About Defining an OCI Connection Pool

24-3

OracleOCIConnectionPool cpool = new OracleOCIConnectionPool

("HR", "hr", "jdbc:oracle:oci:@(description=(address=(host=

localhost)(protocol=tcp)(port=5221))(connect_data=(INSTANCE_NAME=orcl)))",

poolConfig);

poolConfig

is a set of properties that specify the connection pool. If

poolConfig

is null,

then the default values are used. For example, consider the following:

•

poolConfig.put (OracleOCIConnectionPool.CONNPOOL_MIN_LIMIT, "4");

•

poolConfig.put (OracleOCIConnectionPool.CONNPOOL_MAX_LIMIT, "10");

•

poolConfig.put (OracleOCIConnectionPool.CONNPOOL_INCREMENT, "2");

As an alternative to the constructor call, you can create an instance of the

OracleOCIConnectionPool

class using individual methods to specify the user,

password, and connection string.

OracleOCIConnectionPool cpool = new OracleOCIConnectionPool ( );

cpool.setUser("HR");

cpool.setPassword("hr");

cpool.setURL("jdbc:oracle:oci:@(description=(address=(host=

localhost)(protocol=tcp)(port=5221))(connect_data=(INSTANCE_NAME=orcl)))");

cpool.setPoolConfig(poolConfig); // In case you want to specify a different

// configuration other than the default

// values.

24.3.4 Setting the OCI Connection Pool Parameters

The connection pool configuration is determined by the following

OracleOCIConnectionPool

class attributes:

•

CONNPOOL_MIN_LIMIT

Specifies the minimum number of physical connections that can be maintained by

the pool.

•

CONNPOOL_MAX_LIMIT

Specifies the maximum number of physical connections that can be maintained by

the pool.

•

CONNPOOL_INCREMENT

Specifies the incremental number of physical connections to be opened when all

the existing ones are busy and a call needs one more connection; the increment is

done only when the total number of open physical connections is less than the

maximum number that can be opened in that pool.

•

CONNPOOL_TIMEOUT

Specifies how much time must pass before an idle physical connection is

disconnected; this does not affect a logical connection.

•

CONNPOOL_NOWAIT

Specifies, if enabled, that an error is returned if a call needs a physical connection

while the maximum number of connections in the pool are busy. If disabled, a call

waits until a connection is available. Once this attribute is set to

true

, it cannot be

reset to

false

You can configure all of these attributes dynamically. Therefore, an application has the

flexibility of reading the current load, that is number of open connections and number

Chapter 24

About Defining an OCI Connection Pool

24-4

of busy connections, and adjusting these attributes appropriately, using the

setPoolConfig

method.

Note:

The default values for the

CONNPOOL_MIN_LIMIT

CONNPOOL_MAX_LIMIT

, and

CONNPOOL_INCREMENT

parameters are

, and

, respectively.

The

setPoolConfig

method is used to configure OCI connection pool properties. The

following is a typical example of how the

OracleOCIConnectionPool

class attributes can be

set:

...

java.util.Properties p = new java.util.Properties( );

p.put (OracleOCIConnectionPool.CONNPOOL_MIN_LIMIT, "1");

p.put (OracleOCIConnectionPool.CONNPOOL_MAX_LIMIT, "5");

p.put (OracleOCIConnectionPool.CONNPOOL_INCREMENT, "2");

p.put (OracleOCIConnectionPool.CONNPOOL_TIMEOUT, "10");

p.put (OracleOCIConnectionPool.CONNPOOL_NOWAIT, "true");

cpool.setPoolConfig(p);

...

Observe the following rules when setting these attributes:

•

CONNPOOL_MIN_LIMIT

CONNPOOL_MAX_LIMIT

, and

CONNPOOL_INCREMENT

are mandatory.

•

CONNPOOL_MIN_LIMIT

must be a value greater than zero.

•

CONNPOOL_MAX_LIMIT

must be a value greater than or equal to

CONNPOOL_MIN_LIMIT

plus

CONNPOOL_INCREMENT

•

CONNPOOL_INCREMENT

must be a value greater than or equal to zero.

•

CONNPOOL_TIMEOUT

must be a value greater than zero.

•

CONNPOOL_NOWAIT

must be

true

false.

See Also:

Oracle Call Interface Programmer's Guide

24.3.5 Checking the OCI Connection Pool Status

To check the status of the connection pool, use the following methods from the

OracleOCIConnectionPool

class:

•

int getMinLimit()

Retrieves the minimum number of physical connections that can be maintained by the

pool.

•

int getMaxLimit()

Chapter 24

About Defining an OCI Connection Pool

24-5

Retrieves the maximum number of physical connections that can be maintained by

the pool.

•

int getConnectionIncrement()

Retrieves the incremental number of physical connections to be opened when all

the existing ones are busy and a call needs a connection.

•

int getTimeout()

Retrieves the specified time (in seconds) that a physical connection in a pool can

remain idle before it is disconnected; the age of a connection is based on the

Least Recently Used (LRU) algorithm.

•

String getNoWait()

Retrieves if the

NOWAIT

property is enabled. It returns a string of "

true

" or "

false

•

int getPoolSize()

Retrieves the number of physical connections that are open. This should be used

only as an estimate and for statistical analysis.

•

int getActiveSize()

Retrieves the number of physical connections that are open and busy. This should

be used only as an estimate and for statistical analysis.

•

boolean isPoolCreated()

Retrieves if the pool has been created. The pool is actually created when

OracleOCIConnection(user, password, url, poolConfig)

is called or when

setUser

setPassword

, and

setURL

has been done after calling

OracleOCIConnection()

24.4 About Connecting to an OCI Connection Pool

The

OracleOCIConnectionPool

class, through a

getConnection

method call, creates

an instance of the

OracleOCIConnection

class. This instance represents a connection.

Because the

OracleOCIConnection

class extends

OracleConnection

class, it has the

functionality of this class too. Close the

OracleOCIConnection

objects once the user

session is over, otherwise, they are closed when the pool instance is closed.

There are two ways of calling

getConnection

•

OracleConnection getConnection()

If you do not supply the user name and password, then the default user name and

password used for the creation of the connection pool are used while creating the

connection objects.

•

OracleConnection getConnection(String user, String password)

If you this method, you will get a logical connection identified with the specified

user name and password, which can be different from that used for pool creation.

The following code shows the signatures of the overloaded

getConnection

method:

public synchronized OracleConnection getConnection( )

throws SQLException

Chapter 24

About Connecting to an OCI Connection Pool

24-6

* For getting a connection to the database.

* @param us Connection user-id

* @param p Connection password

* @return connection object

public synchronized OracleConnection getConnection(String us, String p)

throws SQLException

As an enhancement to

OracleConnection

, the following new method is added into

OracleOCIConnection

as a way to change the password for the user:

void passwordChange (String user, String oldPassword, String newPassword)

24.5 Sample Code for OCI Connection Pooling

The following code illustrates the use of OCI connection pooling in a sample application:

import java.sql.DriverManager;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.Properties;

import oracle.jdbc.OracleDriver;

import oracle.jdbc.pool.OracleOCIConnectionPool;

public class conPoolAppl extends Thread

{

public static final String query = "SELECT object_name FROM all_objects WHERE rownum

< 300";

static public void main(String args[]) throws SQLException

{

int _maxCount = 10;

Connection []conn = new Connection[_maxCount];

try

{

String s = null; //System.getProperty ("JDBC_URL");

String url = "jdbc:oracle:oci8:@localhost";

OracleOCIConnectionPool cpool = new OracleOCIConnectionPool("HR", "hr", url,

null);

// Print out the default configuration for the OracleOCIConnectionPool

System.out.println ("-- The default configuration for the

OracleOCIConnectionPool --");

displayPoolConfig(cpool);

//Set up the initial pool configuration

Properties p1 = new Properties();

p1.put (OracleOCIConnectionPool.CONNPOOL_MIN_LIMIT, Integer.toString(1));

p1.put (OracleOCIConnectionPool.CONNPOOL_MAX_LIMIT, Integer.toString(_maxCount));

p1.put (OracleOCIConnectionPool.CONNPOOL_INCREMENT, Integer.toString(1));

// Enable the initial configuration

cpool.setPoolConfig(p1);

Thread []t = new Thread[_maxCount];

for (int i = 0; i < _maxCount; ++i)

{

conn[i] = cpool.getConnection("HR", "hr");

Chapter 24

Sample Code for OCI Connection Pooling

24-7

if ( conn[i] == null )

{

System.out.println("Unable to create connection.");

return;

}

t[i] = new conPoolAppl (i, conn[i]);

t[i].start ();

//displayPoolConfig(cpool);

}

((conPoolAppl)t[0]).startAllThreads ();

try

{

Thread.sleep (200);

}

catch (Exception ea) {}

displayPoolConfig(cpool);

for (int i = 0; i < _maxCount; ++i)

t[i].join ();

}

catch(Exception ex)

{

System.out.println("Error: " + ex);

ex.printStackTrace ();

return;

}

finally

{

for (int i = 0; i < _maxCount; ++i)

if (conn[i] != null)

conn[i].close ();

}

} //end of main

private Connection m_conn;

private static boolean m_startThread = false;

private int m_threadId;

public conPoolAppl (int i, Connection conn)

{

m_threadId = i;

m_conn = conn;

}

public void startAllThreads ()

{

m_startThread = true;

}

public void run ()

{

while (!m_startThread) Thread.yield ();

try

{

doQuery (m_conn);

}

catch (SQLException ea)

{

System.out.println ("*** Thread id: " + m_threadId);

ea.printStackTrace ();

Chapter 24

Sample Code for OCI Connection Pooling

24-8

}

} // end of run

private static void doQuery (Connection conn) throws SQLException

{

PreparedStatement pstmt = null;

ResultSet rs = null;

try

{

pstmt = conn.prepareStatement (query);

rs = pstmt.executeQuery ();

while (rs.next ())

{

//System.out.println ("Object name: " +rs.getString (1));

}

catch (Exception ea)

{

System.out.println ("Error during execution: " +ea);

ea.printStackTrace ();

}

finally

{

if (rs != null)

rs.close ();

if (pstmt != null)

pstmt.close ();

if (conn != null)

conn.close ();

}

} // end of doQuery (Connection)

// Display the current status of the OracleOCIConnectionPool

private static void displayPoolConfig (OracleOCIConnectionPool cpool) throws

SQLException

{

System.out.println (" Min poolsize Limit: " + cpool.getMinLimit());

System.out.println (" Max poolsize Limit: " + cpool.getMaxLimit());

System.out.println (" Connection Increment: " + cpool.getConnectionIncrement());

System.out.println (" NoWait: " + cpool.getNoWait());

System.out.println (" Timeout: " + cpool.getTimeout());

System.out.println (" PoolSize: " + cpool.getPoolSize());

System.out.println (" ActiveSize: " + cpool.getActiveSize());

}

} // end of class conPoolAppl

24.6 Statement Handling and Caching

Statement caching is supported with

OracleOCIConnectionPool

. The caching improves

performance by not having to open, parse, and close cursors. When

OracleOCIConnection.prepareStatement

a_SQL_query

") is processed, the statement cache

is searched for a statement that matches the SQL query. If a match is found, then you can

reuse the

Statement

object instead of incurring the cost of creating another

Statement

object.

The cache size can be dynamically increased or decreased. The default cache size is zero.

Chapter 24

Statement Handling and Caching

24-9

Note:

The

OracleStatement

object created from

OracleOCIConnection

has the

same behavior as one that is created from

OracleConnection

24.7 JNDI and the OCI Connection Pool

The Java Naming and Directory Interface (JNDI) feature makes the properties of a

Java object persist, therefore these properties can be used to construct a new

instance of the object, such as cloning the object. The benefit is that the old object can

be freed, and at a later time a new object with exactly the same properties can be

created. The

InitialContext.bind

method makes the properties persist, either on file

or in a database, while the

InitialContext.lookup

method retrieves the properties

from the persistent store and creates a new object with these properties.

OracleOCIConnectionPool

objects can be bound and looked up using the JNDI

feature. No new interface calls in

OracleOCIConnectionPool

are necessary.

Chapter 24

JNDI and the OCI Connection Pool

24-10

Database Resident Connection Pooling

Database Resident Connection Pool (DRCP) is a connection pool in the server, which many

clients can share. You should use DRCP when the number of active connections, at a given

point of time, is reasonably less than the number of open connections. DRCP is particularly

useful for applications with a large number of middle-tier servers. The Database Resident

Connection Pooling feature increases Database server scalability and resolves the resource

wastage issues of middle-tier connection pooling.

This chapter contains the following sections:

• Overview of Database Resident Connection Pooling

• Enabling Database Resident Connection Pooling

• Pooled Server Processes Across Multiple Connection Pools

• Tagging Support in Database Resident Connection Pooling

• APIs for Using Database Resident Connection Pooling

25.1 Overview of Database Resident Connection Pooling

In middle-tier connection pools, every connection pool maintains a minimum number of open

connections to the server. Each open connection represents resources that are in use at the

server. However, your application does not use all the open connections at a given point of

time, which means that there are unused resources that consume server resources

unnecessarily. In a multiple middle-tier scenario, every middle tier maintains an individual

connection pool, without sharing connections with other middle-tier connection pools, and

retains the open connections for long, even if some of those are inactive. For an application

with a large number of middle-tier connection pools, the number of inactive connections to

the Database server is significantly large in such case, which wastes a lot of Database

resources.

For example, if in your application, the minimum pool size is 200 for every middle-tier

connection pool, the connection pool has 200 open connections to the server, and the

Database server has 200 server processes associated with these connections. If you have 30

similar middle-tier connection pools in your application, then the server has 6000 (200 * 30)

corresponding server processes running at any given point of time. Typically, on an average

only 5% of the connections, and in turn, server processes are in use simultaneously. So, out

of the 6,000 server processes, only 300 server processes are active at any given time. This

leads to 5,700 unused processes on the server, resulting in wasted resources on the server.

The Database Resident Connection Pool implementation creates a pool on the Database

server side, which is shared across multiple client pools. This significantly lowers memory

consumption on the Database server because of reduced number of server processes

running simultaneously and increases its scalability.

25-1

See Also:

• Oracle Database Concepts

• Oracle Database Administrator’s Guide

25.2 Enabling Database Resident Connection Pooling

This section describes how to enable Database Resident Connection Pooling (DRCP)

on the server side and the client side:

• Enabling DRCP on the Server Side

• Enabling DRCP on the Client Side

25.2.1 Enabling DRCP on the Server Side

You must be a database administrator (DBA) and must log on as

SYSDBA

to start and

end a Database Resident Connection Pool (DRCP). This section discusses the

following related concepts:

• Starting a Database Resident Connection Pool

• Configuring a Database Resident Connection Pool

• Ending a Database Resident Connection Pool

• Setting the Statement Cache Size

Note:

You can leverage the DRCP features only with a connection pool on the

client because JDBC does not have a default pool on its own.

Starting a Database Resident Connection Pool

Run the

start_pool

method in the

DBMS_CONNECTION_POOL

package with the default

settings to start the default Oracle Database resident connection pool, namely,

SYS_DEFAULT_CONNECTION_POOL

. For example:

sqlplus /nolog

connect / as sysdba

execute dbms_connection_pool.start_pool();

Configuring a Database Resident Connection Pool

Use the procedures in the

DBMS_CONNECTION_POOL

package to configure the default

Oracle Database resident connection pool. By default, this connection pool uses

default parameter values.

Chapter 25

Enabling Database Resident Connection Pooling

25-2

See Also:

• DBMS_CONNECTION_POOL

• Configuring Database Resident Connection Pooling

Ending a Database Resident Connection Pool

Run the

stop_pool

method in the

DBMS_CONNECTION_POOL

package to end the pool. For

example:

sqlplus /nolog

connect / as sysdba

execute dbms_connection_pool.stop_pool();

Setting the Statement Cache Size

If you use DRCP, then the server caches statement information on the server side. So, you

must specify the statement cache size on the server side in the following way, where 50 is the

preferred size:

execute DBMS_CONNECTION_POOL.CONFIGURE_POOL (session_cached_cursors=>50);

Related Topics

• About Statement Caching

25.2.2 Enabling DRCP on the Client Side

Perform the following steps to enable DRCP on the client side:

Note:

The example in this section uses Universal Connection Pool (UCP) as the client-

side connection pool. For any other connection pool, you must use

oracle.jdbc.pool.OracleConnectionPoolDataSource

as the connection factory.

• Pass a non-null and non-empty

String

value to the

oracle.jdbc.DRCPConnectionClass

connection property

• Append (

SERVER=POOLED

) to the

CONNECT_DATA

configuration parameter in the long

connection string

You can also specify

(<service_name>=POOLED)

in the short connection string in the following

way:

jdbc:oracle:thin:@//<host>:<port>/<service_name>[:POOLED]

For example:

jdbc:oracle:thin:@//localhost:5221/orcl:POOLED

The following code snippet shows how to enable DRCP on the client side:

Chapter 25

Enabling Database Resident Connection Pooling

25-3

Note:

In UCP, if you do not provide a connection class, then the connection pool

name is used as the connection class name by default.

Example 25-1 Enabling DRCP on Client Side Using Universal Connection Pool

String url = "jdbc:oracle:thin:@//localhost:5521/orcl:POOLED";

PoolDataSource pds = PoolDataSourceFactory.getPoolDataSource();

pds.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource");

// Set DataSource Property

pds.setUser("HR");

pds.setPassword("hr");

System.out.println ("Connecting to " + url);

pds.setURL(url);

pds.setConnectionPoolName("HR-Pool1");

pds.setMinPoolSize(2);

pds.setMaxPoolSize(3);

pds.setInitialPoolSize(2);

Properties prop = new Properties();

prop.put("oracle.jdbc.DRCPConnectionClass", "HR-Pool1");

pds.setConnectionProperties(prop);

25.3 Pooled Server Processes Across Multiple Connection

Pools

You can set the same Database Resident Connection Pool (DRCP) connection class

name for all the pooled server processes on the server and share those across

multiple connection pools on the server. For setting the DRCP connection class name,

use the

oracle.jdbc.DRCPConnectionClass

connection property.

25.4 Tagging Support in Database Resident Connection

Pooling

Database Resident Connection Pooling (DRCP) provides an option to associate a

server process with a particular tag name. You can apply a tag to a given connection

and retrieve that tagged connection later. Connection tagging enhances session

pooling because you can retrieve specific sessions easily.

DRCP also provides support for multiple tagging, which is disabled by default. Set the

oracle.jdbc.UseDRCPMultipletag

connection property to

TRUE

for enabling this

feature in your DRCP application.

Once you enable the multiple tagging feature, you can use the same APIs for setting

single or multiple DRCP tags. The only difference between both the cases is the

separator. You must separate the key and the value of a DRCP tag by an equal (

)

character, whereas, you must separate multiple tags from one another by a semi-colon

(

;

) character.

Remember the following points while working with DRCP tags:

• You cannot specify the key or the value of a tag as null or empty.

Chapter 25

Pooled Server Processes Across Multiple Connection Pools

25-4

• When you specify multiple tags, then the leftmost tag has the highest priority and the

rightmost tag has the lowest priority.

• While retrieving a tagged connection, if a complete match is not found (all tags are not

matched), then it searches for a partial match.

See Also:

Oracle Call Interface Programmer's Guide for more information about session

pooling and connection tagging

25.5 PL/SQL Callback for Session State Fix Up

Starting from Oracle Database 12c Release 2 (12.2.0.1), a PL/SQL based fix-up callback for

the session state can be provided on the server. This application-provided callback

transforms a session checked out from the pool to the desired state requested by the

application. This callback works with or without Database Resident Connection Pooling

(DRCP).

Note:

The PL/SQL based fix-up callback is only applicable for multiple tagging.

Using this callback can improve the performance of your application because the fix-up logic

is run for the session state on the server. So, this feature eliminates application round-trips to

the database for the fix-up logic. An appropriate installation user, who must be granted

execute permissions on the related package, should register the fix-up callback during

application installation.

Example 25-2 Example of PL/SQL Fix-Up Callback

Following is an example implementation of the PL/SQL fix up callback to fix up the session

properties

SCHEMA

and

CURRENCY

CREATE OR REPLACE PACKAGE mycb_pack AS

PROCEDURE mycallback (

desired_props IN VARCHAR2,

actual_props IN VARCHAR2

);

END;

CREATE OR REPLACE PACKAGE BODY mycb_pack AS

PROCEDURE mycallback (

desired_props IN VARCHAR2,

actual_props IN VARCHAR2

) IS

property VARCHAR2(64);

key VARCHAR2(64);

value VARCHAR2(64);

Chapter 25

PL/SQL Callback for Session State Fix Up

25-5

pos number;

pos2 number;

pos3 number;

idx1 number;

BEGIN

idx1:=1;

pos:=1;

pos2:=1;

pos3:=1;

property := 'tmp';

-- To check if desired properties are part of actual properties

while (pos > 0 and length(desired_props)>pos)

loop

pos := instr (desired_props, ';', 1, idx1);

if (pos=0)

then

property := substr (desired_props, pos2);

else

property := substr (desired_props, pos2, pos-pos2);

end if ;

pos2 := pos+1;

pos3 := instr (property, '=', 1, 1);

key := substr (property, 1, pos3-1);

value := substr (property, pos3+1);

if (key = 'CURRENCY') then

EXECUTE IMMEDIATE 'ALTER SESSION SET NLS_CURRENCY=''' || value || '''';

elsif (key = 'SCHEMA') then

EXECUTE IMMEDIATE 'ALTER SESSION SET CURRENT_SCHEMA=' || value;

end if;

idx1 := idx1+1;

end loop;

END; -- mycallback

END mycb_pack;

See Also:

Oracle Database JDBC Java API Reference

25.6 APIs for Using Database Resident Connection Pooling

If you want to take advantage of Database Resident Connection Pooling (DRCP) with

higher granular control for your custom connection pool implementations, then you

must use the following APIs declared in the

oracle.jdbc.OracleConnection

interfaces:

•

attachServerConnection

•

detachServerConnection

Chapter 25

APIs for Using Database Resident Connection Pooling

25-6

•

isDRCPEnabled

•

isDRCPMultitagEnabled

•

getDRCPReturnTag

•

needToPurgeStatementCache

•

getDRCPState

See Also:

Oracle Database JDBC Java API Reference

Chapter 25

APIs for Using Database Resident Connection Pooling

25-7

JDBC Support for Database Sharding

This section describes Oracle JDBC support for the Database Sharding feature.

• Overview of Database Sharding for JDBC Users

• About Building the Sharding Key

• APIs for Database Sharding Support

• JDBC Sharding Example

• Overview of the Sharding Data Source

26.1 Overview of Database Sharding for JDBC Users

Modern web applications face new scalability challenges with huge volumes of data. A

commonly accepted solution to this problem is sharding. Sharding is a data tier architecture,

where data is horizontally partitioned across independent databases. Each database in such

a configuration is called a shard. All shards together make up a single logical database,

which is referred to as a sharded database (SDB). Sharding is a shared-nothing database

architecture because shards do not share physical resources such as CPU, memory, or

storage devices.

Sharding uses Global Data Services (GDS), where GDS routes a client request to an

appropriate database based on parameters such as availability, load, network latency, and

replication lag. A GDS pool is a set of replicated databases that offer the same global service.

The databases in a GDS pool can be located in multiple data centers across different regions.

A sharded GDS pool contains all shards of a sharded database and their replicas, and

appears as a single sharded database to database clients.

Starting from Oracle Database 12c Release 2 (12.2.0.1), Oracle JDBC supports database

sharding. The JDBC driver recognizes the specified sharding key and super sharding key and

connects to the relevant shard that contains the data. Once the connection is established to a

shard, then any database operations, such as DMLs, SQL queries and so on, are supported

and executed in the usual way. The following section describes the sharding terminologies

used in this guide:

See Also:

Oracle Database Administrator’s Guide

Sharding, Shard, and Sharded Database

Sharding is a data tier architecture where data is horizontally partitioned across independent

databases. Each database in such configuration is called a shard. All shards together make

up a single logical database which is referred to as a sharded database (SDB).

26-1

Sharding Key, Composite Sharding Key, and Super Sharding Key

A sharding key is a partitioning key used in single-level sharding by range, list, or

consistent hash. All sharding keys together are referred to as the composite sharding

keys. A super-sharding key is the partitioning key used in composite sharding for the

top-level sharding by range or list. Both the sharding key and the super sharding key

can contain one or more columns that determine the shard where each row is stored.

A sharding key can be of type VARCHAR2, CHAR, DATE, NUMBER, TIMESTAMP

and so on.

For JDBC users, it is recommended that sharding keys and super sharding keys must

be passed while obtaining connections from the database. However, Sharding Keys

can be provided in the connection string as a separate attribute under

CONNECT_DATA

Passing sharding key in the connection string restricts the connections only to one

shard. So, it is not recommended to use this approach. Following code snippet shows

how you can provide Sharding Keys as a separate attribute under

CONNECT_DATA

in the

connection string:

(DESCRIPTION=(…)(CONNECT_DATA=(SERVICE_NAME=ORCL (SHARDING_KEY=…)

(SUPER_SHARDING_KEY=...)))

Note:

You must provide the sharding key compliant to the NLS formatting that is

specified in the database.

Multi Shard Queries

Multi Shard Queries enable routing and processing of queries and transactions that

access data stored on multiple shards. Multi Shard Queries are executed without a

sharding key. Multi Shard Operations are used for simple aggregation of data and

reporting across shards.

Shard Catalog

Shard Catalog is a special database that is used for storing sharded database and

supporting multi shard queries. It also helps in centralized management of a sharded

database.

Shard Director

A shard director is a specific implementation of a global service manager (GSM) that

acts as a regional listener for clients that connect to an SDB and maintains a current

topology map of the SDB. Based on the sharding key passed during a connection

request, it routes the connections to the appropriate shard.

Shard Topology

Shard Topology is the sharding key range mappings stored in a particular shard.

Universal Connection Pool (UCP) can cache shard topology, which enables it to

bypass shard director while establishing connections to shards. So, applications that

you built using UCP get fast path for shards.

Chapter 26

Overview of Database Sharding for JDBC Users

26-2

See Also:

Oracle Universal Connection Pool Developer’s Guide

Chunk

A chunk is a single partition from each table of a table family. It is a unit of data migration

between shards.

Chunk Split

Chunk Split is a process that is required when chunks become too big or only part of a chunk

needs to be migrated to another shard.

Chunk Migration

Chunk migration is the process of moving a chunk from one shard to another, when data or

workload skew occurs without any change in the number of shards. It is initiated by DBA to

eliminate hot spots.

Resharding

Resharding is the process of redistributing data between shards triggered by a change in the

number of shards. Chunks are moved between shards for even distribution of chunks across

shards. However, content of chunks does not change, that is, no rehashing takes place

during Resharding.

26.2 About Building the Sharding Key

The shard aware applications must identify and build the sharding key and the super

sharding key, which are required to establish a connection to the sharded database. For

achieving this, the shard aware applications must use the

OracleShardingKey

and the

OracleShardingKeyBuilder

interfaces.

The

OracleShardingKeyBuilder

uses the following builder method for supporting compound

keys with different data types:

subkey(Object subkey, java.sql.SQLTYPE subkeyDataType)

There are multiple invocations of the

subkey

method on the builder for building a compound

sharding key, where each subkey can be of different data types. The data type can be

defined using the

oracle.jdbc.OracleType

enum or

java.sql.JDBCType

Example 26-1 Building a Sharding Key

The following example shows how to build a sharding key:

import java.sql.Connection;

import java.sql.Date;

import java.sql.SQLException;

import java.sql.Statement;

import oracle.jdbc.OracleShardingKey;

Chapter 26

About Building the Sharding Key

26-3

import oracle.jdbc.OracleType;

import oracle.ucp.jdbc.PoolDataSource;

import oracle.ucp.jdbc.PoolDataSourceFactory;

public class ShardExample

{

public static void main(String[] args) throws SQLException

{

String url =

"jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(HOST=myhost)(PORT=3216)

(PROTOCOL=tcp))(CONNECT_DATA=(SERVICE_NAME=myservice)(REGION=east)))";

String user="testuser1";

String pwd = "password";

PoolDataSource pds = PoolDataSourceFactory.getPoolDataSource();

pds.setURL(url);

pds.setUser(user);

pds.setPassword(pwd);

pds.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource");

pds.setInitialPoolSize(5);

pds.setMinPoolSize(5);

pds.setMaxPoolSize(20);

// build the sharding key object

Date shardingKeyVal = new java.sql.Date(0L);

OracleShardingKey sdkey = pds.createShardingKeyBuilder()

.subkey(shardingKeyVal,

OracleType.DATE)

.build();

Connection conn = pds.createConnectionBuilder()

.shardingKey(sdkey)

.build();

Statement stmt = conn.createStatement();

stmt.execute("... SQL statement here ...");

stmt.close();

conn.close();

}

The following code snippet shows how to build a compound sharding key that consists

of String and Date data types:

...

Date shardingKeyVal = new java.sql.Date(0L);

...

OracleShardingKey shardingKey = datasource.createShardingKeyBuilder()

.subkey("[email protected]", JDBCType.VARCHAR)

.subkey(shardingKeyVal, OracleType.DATE)

.build();

...

Chapter 26

About Building the Sharding Key

26-4

Note:

• There is a fixed set of data types that are valid and supported. If any

unsupported data types are used as keys, then exceptions are thrown. The

following list specifies the supported data types:

–

OracleType.VARCHAR2/JDBCType.VARCHAR

–

OracleType.CHAR/JDBCType.CHAR

–

OracleType.NVARCHAR/JDBCType.NVARCHAR

–

OracleType.NCHAR/JDBCType.NCHAR

–

OracleType.NUMBER/JDBCType.NUMERIC

–

OracleType.FLOAT/ JDBCType.FLOAT

–

OracleType.DATE/ JDBCType.DATE

–

OracleType.TIMESTAMP/JDBCType.TIMESTAMP

–

OracleType.TIMESTAMP_WITH_LOCAL_TIME_ZONE

–

OracleType.RAW

• You must provide a sharding key that is compliant to the NLS formatting

specified in the database.

26.3 APIs for Database Sharding Support

Oracle Database 12c Release 2 (12.2.0.1) introduced a set of APIs for implementing

database sharding. The following sections discuss these APIs in details:

• The OracleShardingKey Interface

• The OracleShardingKeyBuilder Interface

• The OracleConnectionBuilder Interface

• Other New Classes and Methods for Database Sharding Support

26.3.1 The OracleShardingKey Interface

This interface indicates that the current object represents an Oracle sharding key that is to be

used with Oracle sharded database.

Syntax

public interface OracleShardingKey extends Comparable <OracleShardingKey>

Chapter 26

APIs for Database Sharding Support

26-5

26.3.2 The OracleShardingKeyBuilder Interface

OracleShardingKeyBuilder

provides the interface to build the compound sharding key

with subkeys of various supported data types. This interface uses the new JDK 8

builder pattern for building a sharding key.

Syntax

public interface OracleShardingKeyBuilder

Example 26-2 Creating the Sharding Key

OracleDataSource ods = new OracleDataSource();

...

//set datasource properties..

...

OracleShardingKey shardingKey = ods.createShardingKeyBuilder()

.subkey("Customer_Name_XYZ",

JDBCType.VARCHAR)

.subkey(94002, JDBCType.NUMERIC)

.build();

26.3.3 The OracleConnectionBuilder Interface

The

OracleConnectionBuilder

is used for building connection objects with additional

parameters, other than user name and password. For creating a connection, the

builder methods need to be called for each parameter that needs to be part of the

connection request, followed by a

build()

method. The order in which the builder

methods are called is not important. However, if the same builder attribute is applied

more than once, then only the most recent value is considered while building the

connection. The

build()

method of the builder can be called only once on a builder

object.

Syntax

public interface OracleConnectionBuilder

Example 26-3 Creating the Connection Builder

...

OracleDataSource ods=new OracleDataSource();

...

OracleConnection conn = ods.createConnectionBuilder()

.shardingKey(shardingKey)

.superShardingKey(superShardingKey)

.build();

Chapter 26

APIs for Database Sharding Support

26-6

26.3.4 Other New Classes and Methods for Database Sharding Support

This section describes the rest of the new classes and methods introduced for implementing

database sharding support.

New Methods in OracleDataSource Class

The

createConnectionBuilder

and

createShardingKeyBulider

methods have been

introduced in

OracleDataSource

class for database sharding support.

OracleConnectionBuilder createConnectionBuilder() throws SQLException;

OracleShardingKeyBuilder createShardingKeyBuilder()

New Methods in OracleXADataSource Class

The

createConnectionBuilder

method has been introduced in

OracleXADataSource

class

for database sharding support.

OracleConnectionBuilder createConnectionBuilder() throws SQLException;

New Methods in OracleConnection Class

The

setShardingKeyIfValid

and

setShardingKey

methods have been introduced in

OracleConnection

class for database sharding support.

boolean setShardingKeyIfValid(OracleShardingKey shardingKey,

OracleShardingKey superShardingKey, int timeout) throws SQLException;

void setShardingKey(OracleShardingKey shardingKey, OracleShardingKey

superShardingKey) throws SQLException;

New Methods in OracleXAConnection Class

The

setShardingKeyIfValid

and

setShardingKey

methods have been introduced in

OracleConnection

class for database sharding support.

boolean setShardingKeyIfValid(OracleShardingKey shardingKey,

OracleShardingKey superShardingKey, int timeout) throws SQLException;

void setShardingKey(OracleShardingKey shardingKey, OracleShardingKey

superShardingKey) throws SQLException;

26.4 JDBC Sharding Example

The following code snippet shows how to use JDBC sharding APIs:

Chapter 26

JDBC Sharding Example

26-7

Example 26-4 JDBC Sharding Example

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(HOST=myhost)

(PORT=1521)(PROTOCOL=tcp))

(CONNECT_DATA=(SERVICE_NAME=myorcldbservicename)))");

ods.setUser("hr");

ods.setPassword("hr");

// Employee name is the sharding Key in this example.

// Build the Sharding Key using employee name as shown below.

OracleShardingKey employeeNameShardKey =

ods.createShardingKeyBuilder()

.subkey("Mary",

JDBCType.VARCHAR)// First Name

.subkey("Claire",

JDBCType.VARCHAR)// Last Name

.build();

OracleShardingKey locationSuperShardKey =

ods.createShardingKeyBuilder() // Building a super sharding key using

location as the key

.subkey("US",

JDBCType.VARCHAR)

.build();

OracleConnection connection = ods.createConnectionBuilder()

.shardingKey(employeeNameShardKe

.superShardingKey(locationSuperS

hardKey)

.build();

26.5 Overview of the Sharding Data Source

Oracle Database Release 21c introduces a new capability in the JDBC data source

that enables Java connectivity to a sharded database without the need to furnish a

sharding key. So, you do not need to identify and build the sharding key and the super

sharding key to establish a connection.

The new sharding data source scales out to sharded databases transparently as it

does not involve any change to the application code. When the sharding key can be

derived from SQL or PL/SQL, the JDBC driver can identify it without the need for the

application to send the sharding key. For using this data source, you must set the

connection property

oracle.jdbc.useShardingDriverConnection

true

in the

following way:

Properties prop = new Properties();

prop.setProperty("oracle.jdbc.useShardingDriverConnection", "true");

The default value of this connection property is

false

Chapter 26

Overview of the Sharding Data Source

26-8

26.5.1 Benefits of the Sharding Data Source

Following are the benefits of the new sharding data source:

• You do not need to use the sharding APIs to pass the sharding key because the sharding

data source derives the sharding key from the SQL statement.

• You do not need to configure the Universal Connection Pool (UCP) because the sharding

data source uses the auto tune feature of UCP.

• You do not need to check-in or check-out a physical connection for every new sharding

key because the sharding data source does it automatically.

• You do not need to separate cross-shard statements from single-shard statements and

create separate connection pools for them because the sharding data source maintains

those connections pools.

• The sharding data source enables the prepared statement caching and routes the

connection to the direct shard based on the key used in the SQL statement.

• The sharding data source simplifies applications and optimizes application performance

without any code change.

26.5.2 Example: How to Use the Sharding Data Source

The following examples show how to use the sharding data source.

Example 26-5 Using the Sharding Data Source

public class ShardingDriverSample {

public static void main(String[] args) throws SQLException

{

ShardingDriverSample sample = new ShardingDriverSample();

sample.bindQuerySample();

}

private void bindQuerySample() throws SQLException {

OracleConnection conn = getGsmConnection();

executeQueryWithBindAndReadRows(conn, "SELECT * FROM MY_SHARD_TABLE

where ID = ?", 10);

System.out.println("Direct shard execution percentage:" +

conn.getPercentageQueryExecutionOnDirectShard());

}

private OracleConnection getGsmConnection() throws SQLException {

OracleDataSource ds = new OracleDataSource();

ds.setURL(gsmURL);

Properties prop = new Properties();

prop.setProperty("user", <userName>);

prop.setProperty("password", <password>);

// this property enables sharding datasource feature

prop.setProperty("oracle.jdbc.useShardingDriverConnection", "true");

ds.setConnectionProperties(prop);

return ds.getConnection();

}

private void executeQueryWithBindAndReadRows(Connection dbConnection,

Chapter 26

Overview of the Sharding Data Source

26-9

String sql, int noOfTime)

throws SQLException {

while (noOfTime-- > 0) {

PreparedStatement statement = dbConnection.prepareStatement(sql);

statement.setInt(1, 15);

ResultSet rs = statement.executeQuery();

...

}

26.5.3 Limitations of the Sharding Data Source

This section describes the limitations of the sharding data source.

• The sharding data source supports only the JDBC Thin driver. It does not support

the JDBC OCI driver or the KPRB driver.

• The sharding data source does not support some Oracle JDBC extension APIs

such as Direct Path Load, JDBC Dynamic Monitoring Service (DMS) metrics, and

so on.

• The sharding data source supports PL/SQL execution only through the catalog

database.

• When

AUTO COMMIT

is set to

OFF

, then the execution always happens on the

catalog database.

• If the data source property

singleShardTransactionSupport

is set to

TRUE

, then

the sharding data source supports local transactions against a single shard, when

AUTO COMMIT

is set to

OFF

The following code snippet shows how to set the

singleShardTransactionSupport

property:

private OracleDataSource createShardingDataSource() throws

SQLException {

OracleDataSource ds = new OracleDataSource();

Properties prop = new Properties();

prop.setProperty("user", <userName>);

prop.setProperty("password", <password>);

// Set this connection property to enable sharding data source

feature

prop.setProperty("oracle.jdbc.useShardingDriverConnection",

"true");

ds.setConnectionProperties(prop);

ds.setURL(gsmURL);

Chapter 26

Overview of the Sharding Data Source

26-10

// Set this data source property to enable single shard transaction

support

ds.setSingleShardTransactionSupport(true);

return ds;

}

Chapter 26

Overview of the Sharding Data Source

26-11

Oracle Advanced Queuing

Oracle Advanced Queuing (AQ) provides database-integrated message queuing functionality.

It is built on top of Oracle Streams and optimizes the functions of Oracle Database so that

messages can be stored persistently, propagated between queues on different computers

and databases, and transmitted using Oracle Net Services, HTTP, and HTTPS. Because

Oracle AQ is implemented in database tables, all operational benefits of high availability,

scalability, and reliability are also applicable to queue data. This chapter provides information

about the Java interface to Oracle AQ.

Note:

• Oracle Advanced Queuing (AQ) is a feature of the Oracle JDBC Thin driver and

is not supported by JDBC OCI driver.

• In Oracle Database 12c Release 1 (12.1), support for

XMLType

queues has

been added. Till Oracle Database 11g Release 1, supported queue types were

RAW

ADT

, and

ANYDATA

queue types.

See Also:

Oracle Database Advanced Queuing User's Guide

This chapters covers the following topics:

• Functionality and Framework of Oracle Advanced Queuing

• Making Changes to the Database

• AQ Asynchronous Event Notification

• About Creating Messages

• Enqueuing Messages

• Dequeuing Messages

• Examples: Enqueuing and Dequeuing

27.1 Functionality and Framework of Oracle Advanced Queuing

The Oracle JDBC package

oracle.jdbc.aq

provides a fast Java interface to AQ. This

package contains the following:

• Classes

–

AQDequeueOptions

27-1

Specifies the options available for the dequeue operation

–

AQEnqueueOptions

Specifies the options available for the enqueue operation

–

AQFactory

Is a factory class for AQ

–

AQNotificationEvent

Is created whenever a new message is enqueued in a queue for which you

have registered your interest

• Interfaces

–

AQAgent

Used to represent and identify a user of the queue or a producer or consumer

of the message

–

AQMessage

Represents a message that is enqueued or dequeued

–

AQMessageProperties

Contains message properties such as Correlation, Sender, Delay and

Expiration, Recipients, and Priority and Ordering

–

AQNotificationListener

Is a listener interface for receiving AQ notification events

–

AQNotificationRegistration

Represents your interest in being notified when a new message is enqueued

in a particular queue

These classes and interfaces enable you to access an existing queue, create

messages, and enqueue and dequeue messages.

Note:

Oracle JDBC drivers do not provide any API to create a queue. Queues must

be created through the

DBMS_AQADM

PL/SQL package.

See Also:

For more information about the APIs, refer to Oracle Database JDBC Java

API Reference.

27.2 Making Changes to the Database

The code snippets used in this chapter assume that user

is connecting to the

database. Therefore, in the database, you must grant the following privileges to

Chapter 27

Making Changes to the Database

27-2

GRANT EXECUTE ON DBMS_AQ to HR;

GRANT EXECUTE ON DBMS_AQADM to HR;

GRANT AQ_ADMINISTRATOR_ROLE TO HR;

GRANT ADMINISTER DATABASE TRIGGER TO HR;

Before you start enqueuing and dequeuing messages, you must have queues in the

Database. For this, you must perform the following:

1. Create a queue table in the following way:

BEGIN

DBMS_AQADM.CREATE_QUEUE_TABLE(

QUEUE_TABLE =>'HR.RAW_SINGLE_QUEUE_TABLE',

QUEUE_PAYLOAD_TYPE =>'RAW',

COMPATIBLE => '10.0');

END;

2. Create a queue in the following way:

BEGIN

DBMS_AQADM.CREATE_QUEUE(

QUEUE_NAME =>'HR.RAW_SINGLE_QUEUE',

QUEUE_TABLE =>'HR.RAW_SINGLE_QUEUE_TABLE',

END;

3. Start the queue in the following way:

BEGIN

DBMS_AQADM.START_QUEUE(

'HR.RAW_SINGLE_QUEUE',

END;

It is a good practice to stop the queue and remove the queue tables from the database. You

can perform this in the following way:

1. Stop the queue in the following way:

BEGIN

DBMS_AQADM.STOP_QUEUE(

HR.RAW_SINGLE_QUEUE',

END;

2. Remove the queue tables from the database in the following way:

BEGIN

DBMS_AQADM.DROP_QUEUE_TABLE(

QUEUE_TABLE =>'HR.RAW_SINGLE_QUEUE_TABLE',

FORCE => TRUE

END;

27.3 AQ Asynchronous Event Notification

A JDBC application can do the following:

• Register to the AQ namespace and receive notification when an enqueue occurs. This

can be performed in the following way:

public AQNotificationRegistration registerForAQEvents(

OracleConnection conn,

String queueName) throws SQLException

{

Properties globalOptions = new Properties();

String[] queueNameArr = new String[1];

Chapter 27

AQ Asynchronous Event Notification

27-3

queueNameArr[0] = queueName;

Properties[] opt = new Properties[1];

opt[0] = new Properties();

opt[0].setProperty(OracleConnection.NTF_AQ_PAYLOAD,"true");

AQNotificationRegistration[] regArr =

conn.registerAQNotification(queueNameArr,opt,globalOptions);

AQNotificationRegistration reg = regArr[0];

return reg;

}

• Register subscriptions to database events and receive notifications when the

events are triggered

Registered clients are notified asynchronously when events are triggered or on an

explicit AQ enqueue (or a new message is enqueued in a queue for which you

have registered your interest). Clients do not need to be connected to a database.

The following code snippet shows how to subscribe to database events and

receive notifications when the events are triggered:

class DemoAQRawQueueListener implements AQNotificationListener

{

OracleConnection conn;

String queueName;

String typeName;

int eventsCount = 0;

public DemoAQRawQueueListener(String _queueName, String _typeName)

throws SQLException

{

queueName = _queueName;

typeName = _typeName;

conn = (OracleConnection)DriverManager.getConnection

(DemoAQRawQueue.URL, DemoAQRawQueue.USERNAME, DemoAQRawQueue.PASSWORD);

}

public void onAQNotification(AQNotificationEvent e)

{

try

{

AQDequeueOptions deqopt = new AQDequeueOptions();

deqopt.setRetrieveMessageId(true);

if(e.getConsumerName() != null)

deqopt.setConsumerName(e.getConsumerName());

if((e.getMessageProperties()).getDeliveryMode()

== AQMessageProperties.DeliveryMode.BUFFERED)

{

deqopt.setDeliveryMode(AQDequeueOptions.DEQUEUE_BUFFERED);

deqopt.setVisibility(AQDequeueOptions.DEQUEUE_IMMEDIATE);

}

AQMessage msg = conn.dequeue(queueName,deqopt,typeName);

byte[] msgId = msg.getMessageId();

if(msgId != null)

{

String mesgIdStr = DemoAQRawQueue.byteBufferToHexString(msgId,20);

System.out.println("ID of message dequeued = "+mesgIdStr);

}

System.out.println(msg.getMessageProperties().toString());

byte[] payload = msg.getPayload();

if(typeName.equals("RAW"))

{

String payloadStr = new String(payload,0,10);

Chapter 27

AQ Asynchronous Event Notification

27-4

System.out.println("payload.length="+payload.length+", value="+payloadStr);

}

catch(SQLException sqlex)

{

System.out.println(sqlex.getMessage());

}

eventsCount++;

}

public int getEventsCount()

{

return eventsCount;

}

public void closeConnection() throws SQLException

{

conn.close();

}

• Register to the listener in the following way:

AQNotificationRegistration reg = registerForAQEvents(conn,queueName+":BLUE");

DemoAQRawQueueListener demo_li = new DemoAQRawQueueListener(queueName,queueType);

reg.addListener(demo_li);

27.4 About Creating Messages

This section describes the following concepts:

• Creating Messages

• AQ Message Properties

• AQ Message Payload

27.4.1 Creating Messages

Before you enqueue a message, you must create the message. An instance of a class

implementing the

AQMessage

interface represents an AQ message. An AQ message contains

properties (metadata) and a payload (data). Perform the following to create an AQ message:

1. Create an instance of

AQMessageProperties

in the following way:

AQMessageProperties msgprop = AQFactory.createAQMessageProperties();

2. Set the property attributes in the following way:

msgprop.setCorrelation("mycorrelation");

msgprop.setExceptionQueue("MY_EXCEPTION_QUEUE");

msgprop.setExpiration(0);

msgprop.setPriority(1);

3. Create the AQ message using the

AQMessageProperties

object in the following way:

AQMessage mesg = AQFactory.createAQMessage(msgprop);

4. Set the payload in the following way:

byte[] rawPayload = "Example_Payload".getBytes();

mesg.setPayload(new oracle.sql.RAW(rawPayload));

Chapter 27

About Creating Messages

27-5

27.4.2 AQ Message Properties

The properties of the AQ message are represented by an instance of the

AQMessageProperties

interface. You can set or get the following message properties:

• Dequeue Attempts Count: Specifies the number of attempts that have been made

to dequeue the message. This property cannot be set.

• Correlation: Is an identifier supplied by the producer of the message at the time of

enqueuing the message.

• Delay: Is the number of seconds for which the message is in the

WAITING

state.

After the specified delay, the message is in the

READY

state and available for

dequeuing. Dequeuing a message by using the message ID (msgid) overrides the

delay specification.

Note:

Delay is not supported with buffered messaging.

• Delivery Mode: Specifies whether the message is a buffered message or a

persistent message. This property cannot be set.

• Enqueue Time: Specifies the time at which the message was enqueued. This

value is determined by the system and cannot be set by the user.

• Exception Queue: Specifies the name of the queue into which the message is

moved if it cannot be processed successfully. Messages are moved in two cases:

– The number of unsuccessful dequeue attempts has exceeded

max_retries

– The message has expired.

• Expiration: Is the number of seconds during which the message is available for

dequeuing, starting from when the message reaches the

READY

state. If the

message is not dequeued before it expires, then it is moved to the exception

queue in the

EXPIRED

state.

• Message State: Specifies the state of the message at the time of dequeuing the

message. This property cannot be set.

• Previous Queue Message ID: Is the ID of the message in the last queue that

generated the current message. When a message is propagated from one queue

to another, this attribute identifies the ID of the queue from which it was last

propagated. This property cannot be set.

• Priority: Specifies the priority of the message. It can be any integer including

negative integers; the smaller the value, the higher the priority.

• Recipient list: Is a list of

AQAgent

objects that represent the recipients. The default

recipients are the queue subscribers. This parameter is valid only for multiple-

consumer queues.

• Sender: Is an identifier specified by the producer at the time of enqueuing the

message. It is an instance of

AQAgent

• Transaction group: Specifies the transaction group of the message for transaction-

grouped queues. It is set after a successful call to the

dequeueArray

method.

Chapter 27

About Creating Messages

27-6

27.4.3 AQ Message Payload

Depending on the type of the queue, the payload of the AQ message can be specified using

the

setPayload

method of the

AQMessage

interface. The following code snippet illustrates how

to set the payload:

...

byte[] rawPayload = "Example_Payload".getBytes();

mesg.setPayload(new oracle.sql.RAW(rawPayload));

...

You can retrieve the payload of an AQ message using the

getPayload

method or the

appropriate

getXXXPayload

method in the following way:

byte[] payload = mesg.getPayload();

These methods are defined in the

AQMessage

interface.

27.5 Example: Creating a Message and Setting a Payload

This section provides an example that illustrates how to create a message and set a payload.

Example 27-1 Creating a Message and Setting a Payload

This example shows how to Create an instance of

AQMessageProperties

, set the property

attributes, create the AQ message, and set the payload.

AQMessageProperties msgprop = AQFactory.createAQMessageProperties();

msgprop.setCorrelation("mycorrelation");

msgprop.setExceptionQueue("MY_EXCEPTION_QUEUE");

AQAgent ag = AQFactory.createAQAgent();

ag.setName("MY_SENDER_AGENT_NAME");

ag.setAddress("MY_SENDER_AGENT_ADDRESS");

msgprop.setSender(ag);

// handle multi consumer case:

if(recipients != null)

msgprop.setRecipientList(recipients);

System.out.println(msgprop.toString());

AQMessage mesg = AQFactory.createAQMessage(msgprop);

byte[] rawPayload = "Example_Payload".getBytes();

mesg.setPayload(new oracle.sql.RAW(rawPayload));

27.6 Enqueuing Messages

After you create a message and set the message properties and payload, you can enqueue

the message using the

enqueue

method of the

OracleConnection

interface. Before you

enqueue the message, you can specify some enqueue options. The

AQEnqueueOptions

class

enables you to specify the following enqueue options:

• Delivery mode: Specifies the delivery mode. Delivery mode can be set to either persistent

(

ENQUEUE_PERSISTENT

) or buffered (

ENQUEUE_BUFFERED

• Retrieve Message ID: Specifies whether or not the message ID has to be retrieved from

the server when the message has been enqueued. By default, the message ID is not

retrieved.

Chapter 27

Example: Creating a Message and Setting a Payload

27-7

• Transformation: Specifies a transformation that will be applied before enqueuing

the message. The return type of the transformation function must match the type

of the queue.

Note:

Transformations must be created in PL/SQL using

DBMS_TRANSFORM.CREATE_TRANSFORMATION(...)

• Visibility: Specifies the transactional behavior of the enqueue request. The default

value for this option is

ENQUEUE_ON_COMMIT

. It indicates that the enqueue operation

is part of the current transaction.

ENQUEUE_IMMEDIATE

indicates that the enqueue

operation is an autonomous transaction, which commits at the end of the

operation. For buffered messaging, you must use

ENQUEUE_IMMEDIATE

The following code snippet illustrates how to set the enqueue options and enqueue the

message:

...

AQEnqueueOptions opt = new AQEnqueueOptions();opt.setRetrieveMessageId(true);

conn.enqueue(queueName, opt, mesg);

...

27.7 Dequeuing Messages

Enqueued messages can be dequeued using the

dequeue

method of the

OracleConnection

interface. Before you dequeue a message you must set the

dequeue options. The

AQDequeueOptions

class enables you to specify the following

dequeue options:

• Condition: Specifies a conditional expression based on the message properties,

the message data properties, and PL/SQL functions. A dequeue condition is

specified as a

Boolean

expression using syntax similar to the

WHERE

clause of a

SQL query.

• Consumer name: If specified, only the messages matching the consumer name

are accessed.

Note:

If the queue is a single-consumer queue, do not set this option.

• Correlation: Specifies a correlation criterion (or search criterion) for the dequeue

operation.

• Delivery Filter: Specifies the type of message to be dequeued. You dequeue

buffered messages only (

DEQUEUE_BUFFERED

) or persistent messages only

(

DEQUEUE_PERSISTENT

), which is the default, or both

(

DEQUEUE_PERSISTENT_OR_BUFFERED

• Dequeue Message ID: Specifies the message identifier of the message to be

dequeued. This can be used to dequeue a unique message whose ID is known.

Chapter 27

Dequeuing Messages

27-8

• Dequeue mode: Specifies the locking behavior associated with the dequeue operation. It

can take one of the following values:

–

DequeueMode.BROWSE

: Message is dequeued without acquiring any lock.

–

DequeueMode.LOCKED

: Message is dequeued with a write lock that lasts for the

duration of the transaction.

–

DequeueMode.REMOVE

: (default) Message is dequeued and deleted. The message can

be retained in the queue based on the retention properties.

–

DequeueMode.REMOVE_NO_DATA

: Message is marked as updated or deleted.

• Maximum Buffer Length: Specifies the maximum number of bytes that will be allocated

when dequeuing a message from a

RAW

queue. The default maximum is

DEFAULT_MAX_PAYLOAD_LENGTH

but it can be changed to any other nonzero value. If the

buffer is not large enough to contain the entire message, then the exceeding bytes will be

silently ignored.

• Navigation: Specifies the position of the message that will be retrieved. It can take one of

the following values:

–

NavigationOption.FIRST_MESSAGE

: The first available message matching the search

criteria is dequeued.

–

NavigationOption.NEXT_MESSAGE

: (default) The next available message matching

the search criteria is dequeued. If the previous message belongs to a message

group, then the next available message matching the search criteria in the message

group is dequeued.

–

NavigationOption.NEXT_TRANSACTION

: Messages in the current transaction group

are skipped, and the first message of the next transaction group is dequeued. This

setting can be used only if message grouping is enabled for the queue.

• Retrieve Message ID: Specifies whether or not the message identifier of the dequeued

message needs to be retrieved. By default, it is not retrieved.

• Transformation: Specifies a transformation that will be applied after dequeuing the

message. The source type of the transformation must match the type of the queue.

Note:

Transformations must be created in PL/SQL using

DBMS_TRANSFORM.CREATE_TRANSFORMATION(...)

• Visibility: Specifies whether or not the message is dequeued as part of the current

transaction. It can take one of the following values:

–

VisibilityOption.ON_COMMIT

: (default) The dequeue operation is part of the current

transaction.

–

VisibilityOption.IMMEDIATE

: The dequeue operation is an autonomous transaction

that commits at the end of the operation.

Chapter 27

Dequeuing Messages

27-9

Note:

The Visibility option is ignored in the

DequeueMode.BROWSE

dequeue

mode. If the delivery filter is

DEQUEUE_BUFFERED

DEQUEUE_PERSISTENT_OR_BUFFERED

, then this option must be set to

VisibilityOption.IMMEDIATE

• Wait: Specifies the wait time for the dequeue operation, if none of the messages

matches the search criteria. The default value is

DEQUEUE_WAIT_FOREVER

indicating

that the operation waits forever. If set to

DEQUEUE_NO_WAIT

, then the operation does

not wait. If a number is specified, then the dequeue operation waits for the

specified number of seconds.

Note:

If you use

DEQUEUE_WAIT_FOREVER

, then the dequeue operation will not

return until a message that matches the search criterion is available in

the queue. However, you can interrupt the dequeue operation by calling

the

cancel

method on the

OracleConnection

object.

The following code snippet illustrates how to set the dequeue options and dequeue the

message:

...

AQDequeueOptions deqopt = new AQDequeueOptions();

deqopt.setRetrieveMessageId(true);

deqopt.setConsumerName(consumerName);

AQMessage msg = conn.dequeue(queueName,deqopt,queueType);

27.8 Examples: Enqueuing and Dequeuing

This section provides a few examples that illustrate how to enqueue and dequeue

messages.

Example 27-2 illustrates how to enqueue a message, and Example 27-3 illustrates

how to dequeue a message.

Example 27-2 Enqueuing a Single Message

This example illustrates how to obtain access to a queue, create a message, and

enqueue it.

AQMessageProperties msgprop = AQFactory.createAQMessageProperties();

msgprop.setPriority(1);

msgprop.setExceptionQueue("EXCEPTION_QUEUE");

msgprop.setExpiration(0);

AQAgent agent = AQFactory.createAQAgent();

agent.setName("AGENTNAME");

agent.setAddress("AGENTADDRESS");

msgprop.setSender(agent);

AQMessage mesg = AQFactory.createAQMessage(msgprop);

mesg.setPayload(buffer); // where buffer is a byte array (for a RAW queue)

AQEnqueueOptions options = new AQEnqueueOptions();

conn.enqueue("HR.MY_QUEUE", options, mesg);

Chapter 27

Examples: Enqueuing and Dequeuing

27-10

Example 27-3 Dequeuing a Single Message

This example illustrates how to obtain access to a queue, set the dequeue options, and

dequeue the message.

AQDequeueOptions options = new AQDequeueOptions();

options.setDeliveryFilter(AQDequeueOptions.DeliveryFilter.BUFFERED);

AQMessage mesg = conn.dequeue("HR.MY_QUEUE", options, "RAW");

Chapter 27

Examples: Enqueuing and Dequeuing

27-11

Continuous Query Notification

This chapter describes how the Continuous Query Notification feature works.

This chapter describes the following topics:

• Overview of Continuous Query Notification

• Overview of Client Initiated Continuous Query Notification

• Creating a Registration

• Associating a Query with a Registration

• Notifying Database Change Events

• Deleting a Registration

28.1 Overview of Continuous Query Notification

Generally, a middle-tier data cache duplicates some data from the back-end database server,

so that it can avoid redundant queries to the database. However, this is efficient only when

the data rarely changes in the database. The data cache has to be updated or invalidated

when the data changes in the database.

Starting from 11g Release 1, Oracle JDBC drivers provide support for the Continuous Query

Notification feature of Oracle Database. Using this functionality, multitier systems can take

advantage of the Continuous Query Notification feature to maintain a data cache as up-to-

date as possible, by receiving invalidation events from the JDBC drivers.

The JDBC drivers can register SQL queries with the database and receive notifications in

response to the following:

• DML or DDL changes on the objects associated with the queries

• DML or DDL changes that affect the result set

The notifications are published when the DML or DDL transaction commits (changes made in

a local transaction do not generate any event until they are committed).

To use Oracle JDBC driver support for Continuous Query Notification, perform the following:

1. Registration: You first need to create a registration.

2. Query association: After you have created a registration, you can associate SQL queries

with it. These queries are part of the registration.

3. Notification: Notifications are created in response to changes in tables or result set.

Oracle database communicates these notifications to the JDBC drivers through a

dedicated network connection and JDBC drivers convert these notifications to Java

events.

Also, you need to grant the

CHANGE NOTIFICATION

privilege to the user. For example, if you

connect to the database using the

user name, then you need to run the following

command in the database:

28-1

grant change notification to HR;

28.2 Overview of Client Initiated Continuous Query

Notification

Starting from Oracle Database Release 19c, the JDBC Thin driver supports the Client

Initiated Continuous Query Notification feature. In this case, the client application

initiates a connection to the database server for receiving notifications.

A client application first initiates a new database connection before creating a

Continuous Query Notification registration. When the application creates a registration,

the JDBC driver internally starts a new thread and creates a new connection with the

database server. The database server then uses this new connection to send change

notifications to the client.

By default, this feature is disabled for an on-premise database. You must set the

OracleConnection.DCN_CLIENT_INIT_CONNECTION

to true for enabling this feature.

See Also:

Continuous Query Notification Registration Options

28.3 Creating a Registration

Creating a CQN registration is a one-time process and is done outside the currently

used transaction. The API for creating a registration in the server is executed in its

own transaction and is committed immediately.

You need a JDBC connection to create a registration. However, the registration is not

attached to the connection. You can close the connection after creating a registration,

and the registration survives. In an Oracle RAC environment, a registration is a

persistent entity that exists on all nodes. The registration exists in the Database. So,

even if a node goes down, the registration continues to exist and is notified when the

tables change.

There are two ways to create a registration:

• The JDBC-style of registration: Use the JDBC driver to create a registration on the

server. The JDBC driver launches a new thread that listens to notifications from

the server (through a dedicated channel) and converts these notification

messages into Java events. The driver then notifies all the listeners registered with

this registration.

• The PL/SQL-style of registration: If you want a PL/SQL stored procedure to handle

the notifications, then create a PL/SQL-style registration. As in the JDBC-style of

registration, the JDBC drivers enable you to attach statements (queries) to this

registration. However the JDBC drivers do not get notifications from the server

because the notifications are handled by the PL/SQL stored procedure.

Chapter 28

Overview of Client Initiated Continuous Query Notification

28-2

Note:

This approach is useful only for nonmultithreaded languages, such as PHP.

There is no way to remove one particular object (table) from an existing registration. A

workaround would be to either create a new registration without this object or ignore the

events that are related to this object.

You can use the

registerDatabaseChangeNotification

method of the

oracle.jdbc.OracleConnection

interface to create a JDBC-style of registration. You can set

certain registration options through the

options

parameter of this method. The "Continuous

Query Notification Registration Options" table in the following section lists some of the

registration options that can be set. To set these options, use the

java.util.Properties

object. These options are defined in the

oracle.jdbc.OracleConnection

interface. The

registration options have a direct impact on the notification events that the JDBC drivers will

create. The example (at the end of this chapter) illustrates how to use the Continuous Query

Notification feature.

The

registerDatabaseChangeNotification

method creates a new database change

registration in the database server with the given options. It returns a

DatabaseChangeRegistration

object, which can then be used to associate a statement with

this registration. It also opens a listener socket that will be used by the database to send

notifications.

Note:

If a listener socket (created by a different registration) exists, then this socket is

used by the new database change registration as well.

28.3.1 Continuous Query Notification Registration Options

The following table lists the Continuous Query Notification Registration Options:

Table 28-1 Continuous Query Notification Registration Options

Option Description

DCN_IGNORE_DELETEOP

If set to

true

DELETE

operations will not generate any database change

event.

DCN_IGNORE_INSERTOP

If set to

true

INSERT

operations will not generate any database change

event.

DCN_IGNORE_UPDATEOP

If set to

true

UPDATE

operations will not generate any database change

event.

DCN_NOTIFY_CHANGELAG

Specifies the number of transactions by which the client is willing to lag

behind.

Note: If this option is set to any value other than

, then

ROWID

level

granularity of information will not be available in the events, even if the

DCN_NOTIFY_ROWIDS

option is set to

true

DCN_NOTIFY_ROWIDS

Database change events will include row-level details, such as operation

type and

ROWID

Chapter 28

Creating a Registration

28-3

Table 28-1 (Cont.) Continuous Query Notification Registration Options

Option Description

DCN_QUERY_CHANGE_NOTIFICATION

Activates query change notification instead of object change notification.

Note: This option is available only when running against an 11.0

database.

NTF_LOCAL_HOST

Specifies the IP address of the computer that will receive the notifications

from the server.

NTF_LOCAL_TCP_PORT

Specifies the TCP port that the driver should use for the listener socket.

NTF_QOS_PURGE_ON_NTFN

Specifies if the registration should be expunged on the first notification

event.

NTF_QOS_RELIABLE

Specifies whether or not to make the notifications persistent, which

comes at a performance cost.

NTF_TIMEOUT

Specifies the time in seconds after which the registration will be

automatically expunged by the database.

If there exists a registration, then you can also use the

getDatabaseChangeRegistration

method to map the existing registration with a new

DatabaseChangeRegistration

object. This method is particularly useful if you have

created a registration using PL/SQL and want to associate a statement with it.

28.4 Associating a Query with a Registration

After you have created a registration or mapped to an existing registration, you can

associate a query with it. Like creating a registration, associating a query with a

registration is a one-time process and is done outside of the currently used

registration. The query will be associated even if the local transaction is rolled back.

You can associate a query with registration using the

setDatabaseChangeRegistration

method defined in the

OracleStatement

class. This

method takes a

DatabaseChangeRegistration

object as parameter. The following

code snippet illustrates how to associate a query with a registration:

...

// conn is an OracleConnection object.

// prop is a Properties object containing the registration options.

DatabaseChangeRegistration dcr = conn.registerDatabaseChangeNotifictaion(prop);

...

Statement stmt = conn.createStatement();

// associating the query with the registration

((OracleStatement)stmt).setDatabaseChangeRegistration(dcr);

// any query that will be executed with the 'stmt' object will be associated with

// the registration 'dcr' until 'stmt' is closed or

// '((OracleStatement)stmt).setDatabaseChangeRegistration(null);' is executed.

...

28.5 Notifying Database Change Events

To receive Continuous Query Notifications, attach a listener to the registration. When a

database change event occurs, the database server notifies the JDBC driver. The

driver then constructs a new Java event, identifies the registration to be notified, and

notifies the listeners attached to the registration. The event contains the object ID of

Chapter 28

Associating a Query with a Registration

28-4

the database object that has changed and the type of operation that caused the change.

Depending on the registration options, the event may also contain row-level detail

information. The listener code can then use the event to make decisions about the data

cache.

Note:

The listener code must not slow down the JDBC notification mechanism. If the code

is time-consuming, for example, if it refreshes the data cache by querying the

database, then it needs to be executed within its own thread.

You can attach a listener to a registration using the

addListener

method. The following code

snippet illustrates how to attach a listener to a registration:

...

// conn is an OracleConnection object.

// prop is a Properties object containing the registration options.

DatabaseChangeRegistration dcr = conn.registerDatabaseChangeNotifictaion(prop);

...

// Attach the listener to the registration.

// Note: DCNListener is a custom listener and not a predefined or standard

// lsiener

DCNListener list = new DCNListener();

dcr.addListener(list);

...

28.6 Deleting a Registration

You need to explicitly unregister a registration to delete it from the server and release the

resources in the driver. You can unregister a registration using a connection different from

one that was used for creating it. To unregister a registration, you can use the

unregisterDatabaseChangeNotification

method defined in

oracle.jdbc.OracleConnection

You must pass the

DatabaseChangeRegistration

object as a parameter to this method. This

method deletes the registration from the server and the driver and closes the listener socket.

If the registration was created outside of JDBC, say using PL/SQL, then you must pass the

registration ID instead of the

DatabaseChangeRegistration

object. The method will delete the

registration from the server, however, it does not free any resources in the driver.

Example 28-1 illustrates how to use the Continuous Query Notification feature. In this

example, the

user is connecting to the database. Therefore in the database you need to

grant the following privilege to the user:

grant change notification to HR;

This code will also work with Oracle Database 10g Release 2 (10.2). This code uses table

registration. That is, when you register a

SELECT

query, what you register is the name of the

tables involved and not the query itself. In other words, you might select one single row of a

table and if another row is updated, you will be notified although the result of your query has

not changed.

Chapter 28

Deleting a Registration

28-5

In this example, if you leave the registration open instead of closing it, then the

Continuous Query Notification thread continues to run. Now if you run a DML query

that changes the

HR.DEPARTMENTS

table and commit it, say from SQL*Plus, then the

Java program prints the notification.

Example 28-1 Continuous Query Notification

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Properties;

import oracle.jdbc.OracleConnection;

import oracle.jdbc.OracleDriver;

import oracle.jdbc.OracleStatement;

import oracle.jdbc.dcn.DatabaseChangeEvent;

import oracle.jdbc.dcn.DatabaseChangeListener;

import oracle.jdbc.dcn.DatabaseChangeRegistration;

public class DBChangeNotification

{

static final String USERNAME= "HR";

static final String PASSWORD= "hr";

static String URL;

public static void main(String[] argv)

{

if(argv.length < 1)

{

System.out.println("Error: You need to provide the URL in the first

argument.");

System.out.println(" For example: > java -classpath .:ojdbc6.jar

DBChangeNotification \"jdbc:oracle:thin:

@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=yourhost.yourdomain.com)(PORT=5221))

(CONNECT_DATA=

(SERVICE_NAME=orcl)))\"");

System.exit(1);

}

URL = argv[0];

DBChangeNotification demo = new DBChangeNotification();

try

{

demo.run();

}

catch(SQLException mainSQLException )

{

mainSQLException.printStackTrace();

}

void run() throws SQLException

{

OracleConnection conn = connect();

// first step: create a registration on the server:

Properties prop = new Properties();

// if connected through the VPN, you need to provide the TCP address of the

client.

// For example:

// prop.setProperty(OracleConnection.NTF_LOCAL_HOST,"14.14.13.12");

Chapter 28

Deleting a Registration

28-6

// Ask the server to send the ROWIDs as part of the DCN events (small performance

// cost):

prop.setProperty(OracleConnection.DCN_NOTIFY_ROWIDS,"true");

//Set the DCN_QUERY_CHANGE_NOTIFICATION option for query registration with finer

granularity.

prop.setProperty(OracleConnection.DCN_QUERY_CHANGE_NOTIFICATION,"true");

// The following operation does a roundtrip to the database to create a new

// registration for DCN. It sends the client address (ip address and port) that

// the server will use to connect to the client and send the notification

// when necessary. Note that for now the registration is empty (we haven't

registered

// any table). This also opens a new thread in the drivers. This thread will be

// dedicated to DCN (accept connection to the server and dispatch the events to

// the listeners).

DatabaseChangeRegistration dcr = conn.registerDatabaseChangeNotification(prop);

try

{

// add the listenerr:

DCNDemoListener list = new DCNDemoListener(this);

dcr.addListener(list);

// second step: add objects in the registration:

Statement stmt = conn.createStatement();

// associate the statement with the registration:

((OracleStatement)stmt).setDatabaseChangeRegistration(dcr);

ResultSet rs = stmt.executeQuery("select * from dept where deptno='45'");

while (rs.next())

{}

String[] tableNames = dcr.getTables();

for(int i=0;i<tableNames.length;i++)

System.out.println(tableNames[i]+" is part of the registration.");

rs.close();

stmt.close();

}

catch(SQLException ex)

{

// if an exception occurs, we need to close the registration in order

// to interrupt the thread otherwise it will be hanging around.

if(conn != null)

conn.unregisterDatabaseChangeNotification(dcr);

throw ex;

}

finally

{

try

{

// Note that we close the connection!

conn.close();

}

catch(Exception innerex){ innerex.printStackTrace(); }

}

synchronized( this )

{

// The following code modifies the dept table and commits:

try

{

Chapter 28

Deleting a Registration

28-7

OracleConnection conn2 = connect();

conn2.setAutoCommit(false);

Statement stmt2 = conn2.createStatement();

stmt2.executeUpdate("insert into dept (deptno,dname) values ('45','cool

dept')",

Statement.RETURN_GENERATED_KEYS);

ResultSet autoGeneratedKey = stmt2.getGeneratedKeys();

if(autoGeneratedKey.next())

System.out.println("inserted one row with

ROWID="+autoGeneratedKey.getString(1));

stmt2.executeUpdate("insert into dept (deptno,dname) values ('50','fun

dept')",

Statement.RETURN_GENERATED_KEYS);

autoGeneratedKey = stmt2.getGeneratedKeys();

if(autoGeneratedKey.next())

System.out.println("inserted one row with

ROWID="+autoGeneratedKey.getString(1));

stmt2.close();

conn2.commit();

conn2.close();

}

catch(SQLException ex) { ex.printStackTrace(); }

// wait until we get the event

try{ this.wait();} catch( InterruptedException ie ) {}

}

// At the end: close the registration (comment out these 3 lines in order

// to leave the registration open).

OracleConnection conn3 = connect();

conn3.unregisterDatabaseChangeNotification(dcr);

conn3.close();

}

/**

* Creates a connection the database.

OracleConnection connect() throws SQLException

{

OracleDriver dr = new OracleDriver();

Properties prop = new Properties();

prop.setProperty("user",DBChangeNotification.USERNAME);

prop.setProperty("password",DBChangeNotification.PASSWORD);

return (OracleConnection)dr.connect(DBChangeNotification.URL,prop);

}

/**

* DCN listener: it prints out the event details in stdout.

class DCNDemoListener implements DatabaseChangeListener

{

DBChangeNotification demo;

DCNDemoListener(DBChangeNotification dem)

{

demo = dem;

}

public void onDatabaseChangeNotification(DatabaseChangeEvent e)

{

Thread t = Thread.currentThread();

System.out.println("DCNDemoListener: got an event ("+this+" running on

thread "+t+")");

Chapter 28

Deleting a Registration

28-8

System.out.println(e.toString());

synchronized( demo ){ demo.notify();}

}

Chapter 28

Deleting a Registration

28-9

Part VI

High Availability

This section provides information about the high availability features of Oracle Database 12c

Release 2 (12.2.0.1).

Part VI contains the following chapters:

• Transaction Guard for Java

• Application Continuity for Java

• Oracle JDBC Support for FAN Events

• Transparent Application Failover

• Single Client Access Name

Transaction Guard for Java

The Transaction Guard feature of Oracle Database provides a generic infrastructure for at-

most-once execution during planned and unplanned outages and duplicate submissions. This

chapter discusses Transaction Guard for Java in the following sections:

• Overview of Transaction Guard for Java

• Transaction Guard Support for XA Transactions

• Transaction Guard for Java APIs

• Complete Example:Using Transaction Guard APIs

• About Using Server-Side Transaction Guard APIs

29.1 Overview of Transaction Guard for Java

For most of the current applications, determining the outcome of the last commit operation in

a guaranteed and scalable manner, following a communication failure to the server, is an

unsolved problem. In many cases, the applications prompt the end users to follow certain

steps to avoid resubmitting duplicate requests. For example, some applications warn users

not to click the Submit button twice because if it is not followed, then users may

unintentionally purchase the same items twice and submit multiple payments for the same

invoice.

To solve this problem, Transaction Guard for Java provides transaction idempotence, that is,

every transaction has at-most-once execution that prevents applications from submitting

duplicate transactions. You can tag every transaction with a Logical Transaction Identifier

(

LTXID

), which the application can use after the occurrence of a failure to verify whether the

transaction had committed before the failure or not. For example, if the commit calls do not

return, then using the

LTXID

, the application can find out whether the calls succeeded or not.

The Application Continuity for Java feature uses Transaction Guard for Java internally, which

enables transparent session recovery and replay of SQL statements (queries and DMLs)

since the beginning of the in-flight transaction. Application Continuity enables recovery of

work after the occurrence of a planned or unplanned outage and Transaction Guard for Java

ensures transaction idempotence. When an outage occurs, the recovery restores the state

exactly as it was before the failure occurred.

Related Topics

• Application Continuity for Java

29.2 Transaction Guard Support for XA Transactions

Starting from Oracle Database 12c Release 2 (12.2.0.1), Transaction Guard provides support

for XA transactions for one-phase commit optimization, read-only optimization, and

promotable XA. Transaction Guard with XA provides safe replay following recoverable

outages for XA transactions. With the addition of XA support, Transaction Managers can now

provide replay with idempotence enforced more easily using Transaction Guard.

29-1

Note:

For using Transaction Guard with XA, during session check-out from the

connection pool, you must verify that the database version is Oracle 12c

Release 2 (12.2.0.1) and Transaction Guard is enabled.

A new server protocol provides a guaranteed commit outcome when the commit is

one-phase managed by the database, and switches to a disabled mode while the

Transaction Manager coordinates a transaction for that session. The new protocol sets

a status flag in the LTXID that validates and invalidates access to the LTXID, based on

the current transaction owner.

The protocol is intelligent in its handling that XA can encompass many sessions and

many branches for the one XA transaction. As a further challenge, once a branch is

suspended, a session is available for different transactions, while the original

transaction remains active. There is no requirement to prepare or commit XA

transactions on the same session or RAC instance that created the original branches.

Transaction Guard for XA uses the following two new methods for handling commit

outcome at the database for one-phase XA transactions, while the Transaction

Manager continues to handle commit-outcome for two-phase transactions:

• Using the first method, the driver marks the LTXID provisional until a recoverable

error, or any other named condition, occurs on that session. When a recoverable

error (or any other condition) occurs, the LTXID at the client is marked final. The

guaranteed commit outcome is provided only when the LTXID is final at the client,

and at the server that LTXID has a VALID status, indicating that the database

owns that transaction. Any other access attempt returns an error.

• Using the second method, the client driver does not provide the LTXID to the

application until a recoverable error, or other named condition, occurs on that

session.

29.3 How to Use Transaction Guard with XA

This section contains the following sections:

Obtaining the Commit Outcome with Promotable XA

For local transactions, the request obtains an LTXID as the transaction key, when

there is a recoverable exception. When a second branch starts, then the request is

promoted to XA, or converted to XA, and a Global Transaction ID (GTRID) is allocated

to it. If a recoverable outage occurs during commit processing, where the application

does not receive a reply from the Transaction Manager, then the application can ask a

Transaction Manager for the outcome. Most requests to the database use either local

transactions or single branch optimization. When you use either local transactions or

promotable XA, then there is no overhead in round trips and management for XA,

because the majority of the transactions are local. The workflow of these transactions

follows:

1. Prior to converting to XA, transaction processing is local. Authentication,

SELECT

statements, and local transactions carry and use the LTXID of the local

transaction.

Chapter 29

How to Use Transaction Guard with XA

29-2

2. The Transaction Manager allocates a GTRID to the transaction only when it starts to use

XA due to opening a second branch of the transaction.

3. Following a recoverable error, when the application does not receive a commit outcome,

if the transaction is local, then the Transaction Manager can use the LTXID with the

GET_LTXID_OUTCOME

procedure to retrieve the commit outcome and return

COMMITTED

UNCOMMITTED

outcome to the application.

Replaying if Promotable XA Is Added

Before being promoted, promotable XA supports RDBMS commits through calls and settings

that are not supported by static XA. These calls include auto-commit mode, DDL, DCL,

COMMIT embedded in PL/SQL, and COMMIT through remote procedure calls. The COMMIT

outcome for these user calls and modes is controlled by the RDBMS, and following an error,

the commit outcome can be found using Transaction Guard.

Until promoted, the Transaction Manager is unaware whether the request has issued any

COMMIT or not. If the Transaction Manager wishes to replay a request following a

recoverable error, then the Transaction Manager must determine if any RDBMS COMMIT has

occurred. If any RDBMS COMMIT occurs, or can occur, then replay does not happen. The

GET_LTXID_OUTCOME

procedure is insufficient in determining this because the procedure only

reports the current transaction outcome. If the LTXID is changed, then the transaction is

committed. So, the invocation of the LTXID callback indicates that the transaction is

committed.

29.4 Transaction Guard for Java APIs

This section discusses the APIs associated with Transaction Guard for Java for the following

activities:

• Retrieving the Logical Transaction Identifiers

• Retrieving the Updated Logical Transaction Identifiers

29.4.1 Retrieving the Logical Transaction Identifiers

Use the

getLogicalTransactionId

method of the

oracle.jdbc.OracleConnection

interface

to retrieve the current Logical Transaction Identifiers that are sent by the server. This method

call does not make a database round-trip.

Example

OracleConnection oconn = (OracleConnection) ods.getConnection();

...

// Getting the 1st LTXID after connecting

LogicalTransactionId firstLtxid = oconn.getLogicalTransactionId();

29.4.2 Retrieving the Updated Logical Transaction Identifiers

Use the

oracle.jdbc.LogicalTransactionIdEventListener

interface for receiving updates

to Logical Transaction Identifiers. You must implement this interface in your application to

process the Logical Transaction Identifier events.

Chapter 29

Transaction Guard for Java APIs

29-3

29.4.2.1 Registering Event Listeners

Use the

addLogicalTransactionIdEventListener

method to register a listener to the

Logical Transaction Identifier events.

Example

OracleConnection oconn = (OracleConnection) ods.getConnection();

...

// The subsequent LTXID updates can be obtained through the listener

oconn.addLogicalTransactionIdEventListener(this);

You can also use the

addLogicalTransactionIdEventListener(LogicalTransactionIdEventListener

listener, java.util.concurrent.Executor executor)

method to register a listener

with an executor.

29.4.2.2 Unregistering Event Listeners

Use the

removeLogicalTransactionIdEventListener

method to unregister a listener

from the Logical Transaction Identifier events.

Example

OracleConnection oconn = (OracleConnection) ods.getConnection();

...

// The subsequent LTXID updates can be obtained through the listener

oconn.removeLogicalTransactionIdEventListener(this);

29.5 Complete Example:Using Transaction Guard APIs

The following is a complete example using the Transaction Guard APIs.

import oracle.jdbc.pool.OracleDataSource;

import oracle.jdbc.OracleConnection;

import oracle.jdbc.LogicalTransactionId;

import oracle.jdbc.LogicalTransactionIdEvent;

import oracle.jdbc.LogicalTransactionIdEventListener;

public class transactionGuardExample

{

...

OracleDataSource ods = new OracleDataSource();

ods.setURL(url);

ods.setUser("user");

ods.setPassword("password");

OracleConnection oconn = (OracleConnection) ods.getConnection();

// Getting the 1st LTXID after connecting

LogicalTransactionId firstLtxid = oconn.getLogicalTransactionId();

// The subsequent LTXID updates can be obtained via the listener

oconn.addLogicalTransactionIdEventListener(this);

Chapter 29

Complete Example:Using Transaction Guard APIs

29-4

}

public class LtxidListenerImpl

implements LogicalTransactionIdEventListener

{

...

public void onLogicalTransactionIdEvent(LogicalTransactionIdEvent ltxidEvent)

{

LogicalTransactionId newLtxid = ltxidEvent.getLogicalTransactionId();

// process newLtxid ......

}

29.6 About Using Server-Side Transaction Guard APIs

The

DBMS_APP_CONT

package contains the

GET_LTXID_OUTCOME

procedure that contains the

server-side Transaction Guard APIs. This procedure forces the outcome of a transaction. If

the transaction is not committed, then a fake transaction is committed. Otherwise, the state of

the transaction is returned. By default, the

EXECUTE

privilege for this package is granted to

Database Administrators.

Syntax

PROCEDURE GET_LTXID_OUTCOME(CLIENT_LTXID IN RAW,

committed OUT BOOLEAN,

USER_CALL_COMPLETED OUT BOOLEAN);

Input Parameter

CLIENT_LTXID

specifies the

LTXID

from the client driver.

Output Parameter

COMMITTED

specifies that the transaction is committed.

USER_CALL_COMPLETED

specifies that the user call, which committed the transaction, is

complete.

Exceptions

SERVER_AHEAD

is thrown when the server is ahead of the client. So, the transaction is an old

transaction and must have already been committed.

CLIENT_AHEAD

is thrown when the client is ahead of the server. This can only happen if the

server is flashed back or the

LTXID

is corrupted. In either of these situations, the outcome

cannot be determined.

ERROR

is thrown when an error occurs during processing and the outcome cannot be

determined. It specifies the error code raised during the execution of the current procedure.

Example

Example 29-1 shows how you can call the

GET_LTXID_OUTCOME

procedure and find out the

outcome of an

LTXID

Chapter 29

About Using Server-Side Transaction Guard APIs

29-5

Example 29-1 Finding Out the Outcome of an LTXID

...

OracleConnection oconn = (OracleConnection) ods.getConnection();

LogicalTransactionId ltxid = oconn.getLogicalTransactionId();

boolean committed = false;

boolean call_completed = false;

try

{

CallableStatement cstmt = oconn.prepareCall(GET_LTXID_OUTCOME);

cstmt.setObject(1, ltxid);

cstmt.registerOutParameter(2, OracleTypes.BIT);

cstmt.registerOutParameter(3, OracleTypes.BIT);

cstmt.execute();

committed = cstmt.getBoolean(2);

call_completed = cstmt.getBoolean(3);

System.out.println("LTXID committed ? " + committed);

System.out.println("User call completed ? " + call_completed);

}

catch (SQLException sqlexc)

{

System.out.println("Calling GET_LTXID_OUTCOME failed");

sqlexc.printStackTrace();

}

Chapter 29

About Using Server-Side Transaction Guard APIs

29-6

Application Continuity for Java

The outages of the underlying software, hardware, communications, and storage layers can

cause application execution to fail. In the worst cases, the middle-tier servers may need to be

restarted to deal with the logon storms

. To overcome such problems, Oracle Database 12c

Release 1 (12.1) introduced the Application Continuity feature that masks database outages

to the application and end users are not exposed to such outages.

Note:

• You must use Transaction Guard for using this feature.

• Application Continuity is a feature of the Oracle JDBC Thin driver and is not

supported by JDBC OCI driver.

• Explicit switch of container and service in applications through the

ALTER

SESSION SET CONTAINER

statement is not supported with Application Continuity.

Application Continuity provides a general purpose, application-independent solution that

enables recovery of work from an application perspective, after the occurrence of a planned

or unplanned outage. The outage can be related to system, communication, or hardware

following a repair, a configuration change, or a patch application.

This chapter discusses the JDBC aspect of Application Continuity in the following sections:

• About Configuring Oracle JDBC for Application Continuity for Java

• About Configuring Oracle Database for Application Continuity for Java

• Application Continuity with DRCP

• Application Continuity Support for XA Data Source

• About Identifying Request Boundaries in Application Continuity for Java

• Support for Transparent Application Continuity

• Establishing the Initial State Before Application Continuity Replays

• About Delaying the Reconnection in Application Continuity for Java

• About Retaining Mutable Values in Application Continuity for Java

• Application Continuity Statistics

• About Disabling Replay in Application Continuity for Java

Related Topics

• Transaction Guard for Java

"A logon storm is a sudden increase in the number of client connection requests."

30-1

30.1 About Configuring Oracle JDBC for Application

Continuity for Java

You must use the

oracle.jdbc.replay.OracleDataSourceImpl

oracle.jdbc.replay.OracleConnectio

nPoolDataSourceImpl

, or

oracle.jdbc.replay.driver.OracleXADataSourceImpl

data source to obtain JDBC connections. You can use both

oracle.jdbc.replay.OracleDataSourceImpl

and

oracle.jdbc.replay.OracleConnectionPoolDataSourceImpl

in a standalone manner,

or configure them as connection factories for a connection pool, such as Universal

Connection Pool (UCP), or Oracle WebLogic Server connection pool. Starting from

Oracle Database 12c Release 2 (12.2.0.1), the JDBC Replay Data Source provides a

new data source, the XA Replay Data Source, which supports JDBC operations replay,

and also works with both UCP data source and WebLogic Active GridLink single-pool

data source for all the Oracle RAC features.

For using this data source, your application must implement the

oracle.jdbc.replay.OracleXADataSource

interface. The actual data source

implementation class is

oracle.jdbc.replay.driver.OracleXADataSourceImpl

. You

can specify the implementation class to UCP data sources and Oracle WebLogic

Server GridLink data source as a connection factory. The factory class for JNDI is

oracle.jdbc.replay.OracleXADataSourceFactory

Note:

• The XA replay data source does not provide a configurable replay mode.

For enabling replay, you must use the replay data source and set

FAILOVER_TYPE

TRANSACTION

on the database service at the server

side, if not set already.

• Starting from Oracle Database Release 18c, you can also set

FAILOVER_TYPE

AUTO

for using Transparent Application Continuity.

See Also:

Oracle Real Application Clusters Administration and

Deployment Guide

• For enabling and disabling replay dynamically, you must use a separate

API available on the replay connection proxy. The XA replay data source

does not provide connection pooling. Any

getXAConnection

method call

produces a new JDBC

XAConnection

proxy dynamically, which holds a

new JDBC physical connection as the delegate. The delegate is an

Oracle JDBC driver object.

The following code snippet illustrates the usage of

oracle.jdbc.replay.OracleDataSourceImpl

and

oracle.jdbc.replay.OracleConnectionPoolDataSourceImpl

in a standalone JDBC

application:

Chapter 30

About Configuring Oracle JDBC for Application Continuity for Java

30-2

import java.sql.Connection;

import javax.sql.PooledConnection;

import oracle.jdbc.OracleConnection;

import oracle.jdbc.replay.OracleDataSourceFactory;

import oracle.jdbc.replay.OracleDataSource;

import oracle.jdbc.replay.OracleConnectionPoolDataSource;

...

{

......

OracleDataSource rds = OracleDataSourceFactory.getOracleDataSource();

rds.setUser(user);

rds.setPassword(passwd);

rds.setURL(url);

...... // Other data source configuration like callback, timeouts, etc.

Connection conn = rds.getConnection();

((OracleConnection) conn).beginRequest(); // Explicit request begin

...... // JDBC calls protected by Application Continuity

((OracleConnection) conn).endRequest(); // Explicit request end

conn.close();

OracleConnectionPoolDataSource rcpds =

OracleDataSourceFactory.getOracleConnectionPoolDataSource();

rcpds.setUser(user);

rcpds.setPassword(passwd);

rcpds.setURL(url);

...... // other data source configuration like callback, timeouts, and so on

PooledConnection pc = rcpds.getPooledConnection();

Connection conn2 = pc.getConnection(); // Implicit request begin

...... // JDBC calls protected by Application Continuity

conn2.close(); // Implicit request end

......

You must remember the following points while using the connection URL:

• Always use the thin driver in the connection URL.

• Always connect to a service. Never use

instance_name

or SID because these do not

direct to known good instances and SID is deprecated.

• If the addresses in the

ADDRESS_LIST

at the client does not match the

REMOTE_LISTENER

setting for the database, then it does not connect showing

services cannot be found

So, the addresses in the

ADDRESS_LIST

at the client must match the

REMOTE_LISTENER

setting for the database:

– If

REMOTE_LISTENER

is set to the

SCAN_VIP

, then the

ADDRESS_LIST

uses

SCAN_VIP

– If

REMOTE_LISTENER

is set to the host VIPs, then the

ADDRESS_LIST

uses the same

host VIPs

– If

REMOTE_LISTENER

is set to both

SCAN_VIP

and host VIPs, then the

ADDRESS_LIST

uses

SCAN_VIP

and the same host VIPs

Chapter 30

About Configuring Oracle JDBC for Application Continuity for Java

30-3

Note:

For Oracle clients prior to release 11.2, the

ADDRESS_LIST

must be

upgraded to use SCAN, which means expanding the

ADDRESS_LIST

to three

ADDRESS

entries corresponding to the three SCAN IP

addresses.

If such clients connect to a database that is upgraded from an earlier

release through Database Upgrade Assistant, then you must retain

the

ADDRESS_LIST

of these clients set to the HOST VIPs. However, if

REMOTE_LISTENER

is changed to

ONLY SCAN

, or the clients are moved

to a newly installed Oracle Database 12c Release 1, where

REMOTE_LISTENER

ONLY SCAN

, then they do not get a complete

service map, and may not always be able to connect.

• Set

RETRY_COUNT

RETRY_DELAY

CONNECT_TIMEOUT

, and

TRANSPORT_CONNECT_TIMEOUT

parameters in the connection string. This is a

general recommendation for configuring the JDBC thin driver connections, starting

from Oracle Database Release 12.1.0.2. These settings improve acquiring new

connections at runtime, at replay, and during work drains for planned outages.

The

CONNECT_TIMEOUT

parameter is equivalent to the

SQLNET.OUTBOUND_CONNECT_TIMEOUT

parameter in the

sqlnet.ora

file and applies

to the full connection. The

TRANSPORT_CONNECT_TIMEOUT

parameter applies as per

the

ADDRESS

parameter. If the service is not registered for a failover or restart, then

retrying is important when you use SCAN. For example, for using remote listeners

pointing to SCAN addresses, you should use the following settings:

Note:

In the following code snippets, the

TRANSPORT_CONNECT_TIMEOUT

parameter is set to 3. However, if you are using 12.2.0.1 JDBC driver in

your application, without the required patch that fixes bug 25977056,

then you must set the

TRANSPORT_CONNECT_TIMEOUT

parameter to 3000.

jdbc:oracle:thin:@(DESCRIPTION =

(TRANSPORT_CONNECT_TIMEOUT=3)

(RETRY_COUNT=20)(RETRY_DELAY=3)(FAILOVER=ON)

(ADDRESS_LIST =(ADDRESS=(PROTOCOL=tcp)

(HOST=CLOUD-SCANVIP.example.com)(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=orcl)))

REMOTE_LISTENERS=CLOUD-SCANVIP.example.com:5221

Similarly, for using remote listeners pointing to VIPs at the database, you should

use the following settings:

jdbc:oracle:thin:@(DESCRIPTION =

(TRANSPORT_CONNECT_TIMEOUT=3)

(CONNECT_TIMEOUT=60)(RETRY_COUNT=20)(RETRY_DELAY=3)(FAILOVER=ON)

(ADDRESS_LIST=

(ADDRESS=(PROTOCOL=tcp)(HOST=CLOUD-VIP1.example.com)(PORT=5221) )

(ADDRESS=(PROTOCOL=tcp)(HOST=CLOUD-VIP2.example.com)(PORT=5221) )

Chapter 30

About Configuring Oracle JDBC for Application Continuity for Java

30-4

(ADDRESS=(PROTOCOL=tcp)(HOST=CLOUD-VIP3.example.com)(PORT=5221) ))

(CONNECT_DATA=(SERVICE_NAME=orcl)))

REMOTE_LISTENERS=CLOUD-VIP1.example.com:5221

See Also:

– Oracle Database Net Services Reference for more information about local

naming parameters

– Oracle Real Application Clusters Administration and Deployment Guide

Related Topics

• Data Sources and URLs

30.1.1 Support for Concrete Classes with Application Continuity

Starting from Oracle Database Release 18c, JDBC driver supports the following concrete

classes with Application Continuity:

•

oracle.sql.CLOB

•

oracle.sql.NCLOB

•

oracle.sql.BLOB

•

oracle.sql.BFILE

•

oracle.sql.STRUCT

•

oracle.sql.REF

•

oracle.sql.ARRAY

30.1.2 About Using LONG and LONG RAW columns with Application

Continuity

Typically, Oracle recommends using LOB columns instead of LONG and LONG RAW

columns. This also applies to Application Continuity.

If you have one or more LONG or LONG RAW columns in your table, then the JDBC driver

transfers those to the client in streaming mode, when a query selects those columns. In

streaming mode, the JDBC driver does not read the column data from the network for LONG

or LONG RAW columns, until required. As a result of this, a query involving one or more such

columns can result in a replay failure. So, if there is a situation when you cannot avoid using

such columns, then perform the following tasks to resolve the issue:

See Also:

About Streaming LONG or LONG RAW Columns

Chapter 30

About Configuring Oracle JDBC for Application Continuity for Java

30-5

• Use the

defineColumnType

method to redefine the type of the LONG or LONG

RAW column. For example, if you redefine the LONG or LONG RAW column as

VARCHAR or VARBINARY type, then the driver will not stream the data

automatically.

• Declare the types of all the columns involved in the query.

Note:

If you redefine the column types with the

defineColumnType

method,

then you must declare the types of all the columns involved in the query.

If you do not do so, then the

executeQuery

method will fail.

• Cast the Statement object to

oracle.jdbc.OracleStatement

30.2 About Configuring Oracle Database for Application

Continuity for Java

You must have the following configuration for Oracle Database to use Application

Continuity for Java:

• Use Oracle Database 12c Release 1 (12.1) or later

• If you are using Oracle Real Application Clusters (Oracle RAC) or Oracle Data

Guard, then ensure that FAN is configured with Oracle Notification System (ONS)

to communicate with Oracle WebLogic Server or the Universal Connection Pool

(UCP)

• Use an application service for all database work. To create the service you must:

– Run the

SRVCTL

command if you are using Oracle RAC

– Use the

DBMS_SERVICE

package if you are not using Oracle RAC

• Set the required properties on the service for replay and load balancing. For

example, set:

–

aq_ha_notifications = TRUE

for enabling FAN notification

–

FAILOVER_TYPE = TRANSACTION

FAILOVER_TYPE = AUTO

for using

Application Continuity

–

COMMIT_OUTCOME

TRUE

for enabling Transaction Guard

–

REPLAY_INITIATION_TIMEOUT = 900

for setting the duration in seconds for

which replay will occur

–

FAILOVER_RETRIES = 30

for specifying the number of connection retries for

each replay

–

FAILOVER_DELAY = 10

for specifying the delay in seconds between connection

retries

–

GOAL = SERVICE_TIME

, if you are using Oracle RAC, then this is a

recommended setting

Chapter 30

About Configuring Oracle Database for Application Continuity for Java

30-6

–

CLB_GOAL = LONG

, typically useful for closed workloads. If you are using Oracle RAC,

then this is a recommended setting. For most of the other workloads,

SHORT

is the

recommended setting.

• Do not use the database service, that is, the default service corresponding to the

DB_NAME

DB_UNIQUE_NAME

. This service is reserved for Oracle Enterprise Manager and for

DBAs. Oracle does not recommend the use of the database service for high availability

because this service cannot be:

– Enabled and disabled

– Relocated on Oracle RAC

– Switched over to Oracle Data Guard

See Also:

Oracle Database Development Guide for more information on the operation and

usage of Application Continuity.

30.3 Application Continuity with DRCP

Oracle Database Release 18c JDBC driver supports Application Continuity when Database

Resident Connection Pooling (DRCP) is enabled on the server side. For using Application

Continuity with DRCP, you must configure an application service to a server that uses DRCP.

The following code snippet shows how to use Application Continuity with DRCP:

Example 30-1 Using Application Continuity with DRCP

...

String url = "jdbc:oracle:thin:@(DESCRIPTION =

(TRANSPORT_CONNECT_TIMEOUT=3000)

(RETRY_COUNT=20)(RETRY_DELAY=3)(FAILOVER=ON)

(ADDRESS_LIST =(ADDRESS=(PROTOCOL=tcp)

(HOST=CLOUD-SCANVIP.example.com)(PORT=5221))

(CONNECT_DATA=(SERVICE_NAME=ac-service)

(SERVER=POOLED)))";

PoolDataSource pds = PoolDataSourceFactory.getPoolDataSource();

pds.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource");

// Set DataSource Property

pds.setUser("HR");

pds.setPassword("hr");

System.out.println ("Connecting to " + url);

pds.setURL(url);

pds.setConnectionPoolName("HR-Pool1");

pds.setMinPoolSize(2);

pds.setMaxPoolSize(3);

pds.setInitialPoolSize(2);

Properties prop = new Properties();

prop.put("oracle.jdbc.DRCPConnectionClass", "HR-Pool1");

Chapter 30

Application Continuity with DRCP

30-7

pds.setConnectionProperties(prop);

...

Related Topics

• Overview of Database Resident Connection Pooling

Related Topics

• About Configuring Oracle Database for Application Continuity for Java

30.4 Application Continuity Support for XA Data Source

Oracle Database 12c Release 2 (12.2.0.1) introduced a new feature that enhances

Application Continuity with support for Oracle XA data source

(

javax.sql.XADataSource

), which is similar to non-XA data source

(

javax.sql.DataSource

). Both JDBC and Java Transaction API (JTA) allow a JDBC

connection to interchangeably participate in local and global/XA transactions.

However, many customer applications obtain connections from an XA data source, but

use these connections to perform only local transactions. With the new feature,

Application Continuity also covers applications that are using XA-capable data sources

but with local transactions, including local transactions that are promotable to

global/XA transactions. So, the benefits of Application Continuity, such as, failover and

forward-recovery are extended to these applications.

Note:

You must use Transaction Guard 12.2 for using this feature.

Whenever an underlying physical connection participates in a global/XA transaction, or

engages in any XA operation, replay is disabled on that connection. All other XA

operations function normally, but the application does not get Application Continuity

protection.

Once replay is disabled on a connection for the above reasons, it remains disabled

until the next request begins. Switching from global/XA transaction to local transaction

mode does not automatically reenable replay on a connection.

The following code snippet illustrates how replay is supported for local transactions,

and disabled for XA transaction, when the connections are obtained from

OracleXADataSource

import javax.transaction.xa.*;

import oracle.jdbc.replay.OracleXADataSource;

import oracle.jdbc.replay.OracleXADataSourceFactory;

import oracle.jdbc.replay.ReplayableConnection;

OracleXADataSource xards =

OracleXADataSourceFactory.getOracleXADataSource();

xards.setURL(connectURL);

xards.setUser(<user_name>);

xards.setPassword(<password>);

Chapter 30

Application Continuity Support for XA Data Source

30-8

XAConnection xaconn = xards.getXAConnection();

// Implicit request begins

Connection conn = xaconn.getConnection();

/* Local transaction case */

// Request-boundary detection OFF

((ReplayableConnection) conn).beginRequest();

conn.setAutoCommit(false);

PreparedStatement pstmt=conn.prepareStatement(“select

cust_first_name,cust_last_name from customers where customer_id=1");

ResultSet rs=pstmt.executeQuery();

// Outage happens at this point

// Replay happens at this point

rs.next();

rs.close();

pstmt.close();

((ReplayableConnection) conn).endRequest();

...

/* Global/XA transaction case */

((ReplayableConnection) conn).beginRequest();

conn.setAutoCommit(false);

XAResource xares = xaconn.getXAResource();

Xid xid = createXid();

// Replay is disabled here

xares.start(xid, XAResource.TMNOFLAGS);

conn.prepareStatement(“INSERT INTO TEST_TAB VALUES(200, 'another new

record')”);

// outage happens at this point

try {

//No replay here and throws exception

conn.executeUpdate();

}

// sqlrexc.getNextException() shows the reason for the replay failure

catch (SQLRecoverableException sqlrexc) {

…...

}

30.5 About Identifying Request Boundaries in Application

Continuity for Java

A Request is a unit of work on a physical connection to Oracle Database that is protected by

Application Continuity. Request demarcation varies with specific use-case scenarios. A

request begins when a connection is borrowed from the Universal Connection Pool (UCP) or

Chapter 30

About Identifying Request Boundaries in Application Continuity for Java

30-9

WebLogic Server connection pool, and ends when this connection is returned to the

connection pool.

The JDBC driver provides explicit request boundary declaration APIs

beginRequest

and

endRequest

in the

oracle.jdbc.OracleConnection

interface. These APIs enable

applications, frameworks, and connection pools to indicate to the JDBC Replay Driver

about demarcation points, where it is safe to release the call history, and to enable

replay if it had been disabled by a prior request. At the end of the request, the JDBC

Replay Driver purges the recorded history on the connection, where the API is called.

This helps to further conserve memory consumption for applications that use the same

connections for an extended period of time without returning them to the pool.

For the connection pool to work, the application must get connections when needed,

and release connections when not in use. This scales better and provides request

boundaries transparently. The APIs have no impact on the applications other than

improving resource consumption, recovery, and load balancing performance. These

APIs do not involve altering a connection state by calling any JDBC method, SQL, or

PL/SQL. An error is returned if an attempt is made to begin or end a request while a

local transaction is open.

30.6 Support for Transparent Application Continuity

Oracle Database Release 18c introduced the Transparent Application Continuity

feature, which is a functional mode of Application Continuity. Transparent Application

Continuity transparently tracks and records session and transactional state, so that a

database session can be recovered following recoverable outages. This is performed

safely and without the need for any knowledge of the application or application code

changes. Transparency is achieved by using a state-tracking infrastructure that

categorizes session state usage as an application issues user calls. This feature

enables the driver to detect and inject possible request boundaries, which are known

as implicit request boundaries. For an implicit request boundary:

• No objects are open

• Cursors are returned to the driver statement cache

• No transactions are open

The session state in such a case is known to be restorable. The driver either closes

the current capture and starts a new event, or enables capture if there had been a

disabling event. On the next call to the server, the server verifies and, if applicable,

creates a request boundary, where there was previously no explicit boundary.

To use Transparent Application Continuity, you must set the server-side service

attribute

FAILOVER_TYPE

on the database service to

AUTO

Support for implicit request helps to reduce application failover recovery time and

optimizes Application Continuity. Using Transparent Application Continuity, the server

and the drivers can track transaction and session state usage. However, this feature

should be used with caution for applications that change server session states during

a request. The JDBC Thin driver provides the

oracle.jdbc.enableImplicitRequests

property to turn off implicit requests, if needed. This property can be set at the system

level, which applies to all connections, or at the connection level, which applies to a

particular connection. By default, the value of this property is

true

, which means that

support for implicit request is enabled.

Chapter 30

Support for Transparent Application Continuity

30-10

See Also:

Oracle Real Application Clusters Administration and Deployment Guide

Starting from Oracle Database Release 19c, if you set the value of the

FAILOVER_TYPE

service attribute to

AUTO

, then the Oracle JDBC driver implicitly begins a request on each new

physical connection created through the replay data source. With this feature, applications

using third-party connection pools can use Transparent Application Continuity (TAC) easily,

without making any code change to inject request boundaries.

This implicit

beginRequest

applies only to the replay data source, and only to the physical

connections created during runtime, when TAC is enabled. The driver does not implicitly

begin a request after each reconnection during replay attempts (that is, a

beginRequest

is not

implicitly injected during a replay connection) or in manual Application Continuity mode,

where the

FAILOVER_TYPE

service attribute is set to

TRANSACTION

If you want to turn off this feature explicitly, you can set the value of the Java system property

oracle.jdbc.beginRequestAtConnectionCreation

false.

The default value of this

property is

true

Related Topics

• About Enabling FAILOVER_RESTORE

This section describes how to use the

FAILOVER_RESTORE

service attribute.

30.7 Establishing the Initial State Before Application Continuity

Replays

Non-transactional session state (NTSS) is state of a database session that exists outside

database transactions and is not protected by recovery. For applications that use stateful

requests, the non-transactional state is re-established as the rebuilt session.

For applications that set state only at the beginning of a request, or for stateful applications

that gain performance benefits from using connections with a preset state, one among the

following callback options are provided:

• No Callback

• Connection Labeling

• Connection Initialization Callback

• About Enabling FAILOVER_RESTORE

30.7.1 No Callback

In this scenario, the application builds up its own state during each request.

30.7.2 Connection Labeling

This scenario is applicable only to Universal Connection Pool (UCP) and Oracle WebLogic

server. The application can be modified to take advantage of the preset state on connections.

Chapter 30

Establishing the Initial State Before Application Continuity Replays

30-11

Connection Labeling APIs determine how well a connection matches, and use a

callback to populate the gap when a connection is borrowed.

See Also:

Oracle Universal Connection Pool Developer’s Guide

30.7.3 Connection Initialization Callback

In this scenario, the replay driver uses an application callback to set the initial state of

the session during runtime and replay. The JDBC replay driver provides an optional

connection initialization callback interface as well as methods for registering and

unregistering such callbacks.

When registered, the initialization callback is executed at each successful

reconnection following a recoverable error. An application is responsible for ensuring

that the initialization actions are the same as that on the original connection before

failover. If the callback invocation fails, then replay is disabled on that connection.

This section discusses initialization callbacks in the following sections:

• Creating an Initialization Callback

• Registering an Initialization Callback

• Removing or Unregistering an Initialization Callback

30.7.3.1 Creating an Initialization Callback

To create a JDBC connection initialization callback, an application implements the

oracle.jdbc.replay.ConnectionInitializationCallback

interface. One callback is

allowed for every instance of the

oracle.jdbc.replay.OracleDataSource

interface.

Note:

This callback is only invoked during failover, after a successful reconnection.

Example

The following code snippet demonstrates a simple initialization callback

implementation:

import oracle.jdbc.replay.ConnectionInitializationCallback;

class MyConnectionInitializationCallback implements

ConnectionInitializationCallback

{

public MyConnectionInitializationCallback()

{

...

}

public void initialize(java.sql.Connection connection) throws SQLException

{

// Reset the state for the connection, if necessary (like ALTER SESSION)

Chapter 30

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30-12

...

}

For applications using an XA data source, the connection initialization callback is registered

on the XA replay data source. The callback is executed every time when both of the following

happen:

• A connection is borrowed from the connection pool.

• The replay XA data source gets a new physical connection at failover.

Note:

The connection initialization must be idempotent. If the connection is already

initialized, then it must not repeat itself. This enables applications to reestablish

session initial starting point after a failover and before the starting of replay. The

callback execution must leave an open local transaction without committing it or

rolling it back. If this is violated, an exception is thrown.

If a callback invocation fails, replay is disabled on that connection. For example, an

application embeds the set up phase for a connection in this callback.

30.7.3.2 Registering an Initialization Callback

Use the following method that the JDBC Replay Driver provides in the

oracle.jdbc.replay.OracleDataSource

interface for registering a connection initialization

callback:

registerConnectionInitializationCallback(ConnectionInitializationCallback cbk)

One callback is allowed for every instance of the

OracleDataSource

interface.

For using an XA Data Source, use the

registerConnectionInitializationCallback(ConnectionInitializationCallback cbk)

method in the

oracle.jdbc.replay.OracleXADataSource

interface.

30.7.3.3 Removing or Unregistering an Initialization Callback

Use the following method that the JDBC Replay Driver provides in the

oracle.jdbc.replay.OracleDataSource

interface for unregistering a connection initialization

callback:

unregisterConnectionInitializationCallback(ConnectionInitializationCallback cbk)

For using an XA Data Source, use the

unregisterConnectionInitializationCallback(ConnectionInitializationCallback cbk)

method in the

oracle.jdbc.replay.OracleXADataSource

interface.

30.7.4 About Enabling FAILOVER_RESTORE

This section describes how to use the

FAILOVER_RESTORE

service attribute.

Chapter 30

Establishing the Initial State Before Application Continuity Replays

30-13

FAILOVER_RESTORE

service attribute was introduced in Oracle Database 12c Release 2

(12.2.0.1). Setting the

FAILOVER_RESTORE

attribute to

LEVEL1

automatically restores the

common initial state before replaying a request. By default, the value of the

FAILOVER_RESTORE

attribute is set to

NONE

, which means that it is disabled.

Starting from Oracle Database Release 18c, you can also set the value of this attribute

AUTO

. Also, if you set the value of the

FAILOVER_TYPE

attribute to

AUTO

, then

FAILOVER_RESTORE

is set to

AUTO

automatically. You cannot change the value of

FAILOVER_RESTORE

to anything else as long as

FAILOVER_TYPE

is set to

AUTO

. When

FAILOVER_RESTORE

is set to

AUTO

, then the common initial state is also set. As far as

session state restore is concerned, this setting provides the same function as

FAILOVER_RESTORE

set to

LEVEL1

See Also:

Real Application Clusters Administration and Deployment Guide

Chapter 30

Establishing the Initial State Before Application Continuity Replays

30-14

Note:

For Application Continuity for Java available with Oracle Database Release 21c, the

following initial states are supported for

FAILOVER_RESTORE

•

NLS_CALENDAR

•

NLS_CURRENCY

•

NLS_DATE_FORMAT

•

NLS_DATE_LANGUAGE

•

NLS_DUAL_CURRENCY

•

NLS_ISO_CURRENCY

•

NLS_LANGUAGE

•

NLS_LENGTH_SEMANTICS

•

NLS_NCHAR_CONV_EXCP

•

NLS_NUMERIC_CHARACTER

•

NLS_SORT

•

NLS_TERRITORY

•

NLS_TIME_FORMAT

•

NLS_TIME_TZ_FORMAT

•

NLS_TIMESTAMP_FORMAT

•

NLS_TIMESTAMP_TZ_FORMAT

•

TIME_ZONE (OCI, ODP.NET 12201)

•

CURRENT_SCHEMA

•

MODULE

•

ACTION

•

CLIENT_ID

•

ECONTEXT_ID

•

ECONTEXT_SEQ

•

DB_OP

•

AUTOCOMMIT

states (Java and SQL*Plus)

•

CONTAINER

(PDB) and

SERVICE

for OCI and ODP.NET

In Oracle Database Release 19c, the following additional initial states are supported

for

FAILOVER_RESTORE

•

ERROR_ON_OVERLAP_TIME

•

EDITION

•

SQL_TRANSLATION_PROFILE

•

ROW ARCHIVAL VISIBILITY

Chapter 30

Establishing the Initial State Before Application Continuity Replays

30-15

•

ROLEs

•

CLIENT_INFO

Note:

For Oracle Database Release 19c,

FAILOVER_RESTORE

is automatically

enabled in Transparent Application Continuity (TAC) mode.

The following states are excluded from the auto-restoration option because

they are not supported by the Thin driver:

•

NLS_COMP

•

CALL_COLLECT_TIME

For many applications, enabling

FAILOVER_RESTORE

is sufficient to automatically

restore the initial state required for AC replay, without the use of a callback. If your

application requires any initial state that is not mentioned in the preceding list, or if the

application prefers explicit control over setting the initial state, then the application

must use a callback, either connection labeling or an initialization callback. When a

callback is configured, it overrides the initial states restored by

FAILOVER_RESTORE

, in

case the latter is enabled at the same time.

30.8 About Delaying the Reconnection in Application

Continuity for Java

By default, when JDBC Replay Data Source initiates a failover, the driver attempts to

recover the in-flight work at an instance where the service is available. For doing this,

the driver must first reestablish a good connection to a working instance. This

reconnection can take some time if the database or the instance needs to be restarted

before the service is relocated and published. So, the failover should be delayed until

the service is available from another instance or database.

You must use the

FAILOVER_RETRIES

and

FAILOVER_DELAY

parameters to sustain the

delay because maximum delay is calculated as

FAILOVER_RETRIES

multiplied by

FAILOVER_DELAY

. These parameters can work well in conjunction with a planned

outage, for example, an outage that may make a service unavailable for several

minutes. While setting the

FAILOVER_DELAY

and

FAILOVER_RETRIES

parameters, check

the value of the

REPLAY_INITIAITION_TIMEOUT

parameter first. The default value for

this parameter is 900 seconds. A high value for the

FAILOVER_DELAY

parameter can

cause replay to be canceled.

Parameter Name

Possible Value Default Value

FAILOVER_RETRIES

Positive integer zero or above 30

FAILOVER_DELAY

Time in seconds 10

Chapter 30

About Delaying the Reconnection in Application Continuity for Java

30-16

30.8.1 Configuration Examples Related to Application Continuity for Java

This section provides configuration examples for service creation and modification in the

following subsections:

• Creating Services on Oracle RAC

• Modifying Services on Single-Instance Databases

30.8.1.1 Creating Services on Oracle RAC

If you are using Oracle RAC or Oracle RAC One, then use the

SRVCTL

command to create

and modify services in the following way:

For Transparent Application Continuity

You can create services that use Transparent Application Continuity, as follows:

For policy-managed databases:

$ srvctl add service -db codedb -service GOLD -serverpool ora.Srvpool -

clbgoal SHORT -rlbgoal SERVICE_TIME -failover_restore AUTO -failoverretry 30

-failoverdelay 10 -commit_outcome TRUE -failovertype AUTO -replay_init_time

1800 -retention 86400 -notification TRUE

For administrator-managed databases:

$ srvctl add service -db codedb -service GOLD -preferred serv1 -available

serv2 -clbgoal SHORT -rlbgoal SERVICE_TIME -failover_restore AUTO

-failoverretry 30 -failoverdelay 10 -commit_outcome TRUE -failovertype AUTO -

replay_init_time 1800 -retention 86400 -notification TRUE

For Manual Application Continuity

You can create services that use manual Application Continuity, as follows:

For policy-managed databases:

$ srvctl add service -db codedb -service GOLD -serverpool ora.Srvpool -

clbgoal SHORT -rlbgoal SERVICE_TIME -failover_restore LEVEL1 -failoverretry

-failoverdelay 10 -commit_outcome TRUE -failovertype TRANSACTION -

replay_init_time 1800 -retention 86400 -notification TRUE

For administrator-managed databases:

$ srvctl add service -db codedb -service GOLD -preferred serv1 -available

serv2 -clbgoal SHORT -rlbgoal SERVICE_TIME -failover_restore LEVEL1

-failoverretry 30 -failoverdelay 10 -commit_outcome TRUE -failovertype

TRANSACTION -replay_init_time 1800 -retention 86400 -notification TRUE

Chapter 30

About Delaying the Reconnection in Application Continuity for Java

30-17

30.8.1.2 Modifying Services on Single-Instance Databases

If you are using a single-instance database, then use the

DBMS_SERVICE

package to

modify services in the following way:

declare

params dbms_service.svc_parameter_array;

begin

params('FAILOVER_TYPE'):='TRANSACTION';

params('REPLAY_INITIATION_TIMEOUT'):=1800;

params('RETENTION_TIMEOUT'):=604800;

params('FAILOVER_DELAY'):=10;

params('FAILOVER_RETRIES'):=30;

params('commit_outcome'):='true';

params('aq_ha_notifications'):='true';

dbms_service.modify_service('[your service]',params);

end;

30.9 About Retaining Mutable Values in Application

Continuity for Java

A mutable object is a variable, function return value, or other structure that returns a

different value each time that it is called. For example,

Sequence.NextVal

SYSDATE

SYSTIMESTAMP

, and

SYS_GUID

. To retain the function results for named functions at

replay, the DBA must grant

KEEP

privileges to the user who invokes the function. This

security restriction is imposed to ensure that it is valid for replay to save and restore

function results for code that is not owned by that user.

See Also:

Oracle Database Development Guide

30.9.1 Grant and Revoke Interface

You can work with mutables values by using the standard

GRANT

and

REVOKE

interfaces

in the following way:

• Dates and SYS_GUID Syntax

• Sequence Syntax

• GRANT ALL Statement

• Rules for Grants on Mutable Values

30.9.1.1 Dates and SYS_GUID Syntax

The

DATE_TIME

and

SYS_GUID

syntax is as follows:

GRANT [KEEP DATE TIME|SYSGUID]..[to USER}

REVOKE [KEEP DATE TIME | KEEP SYSGUID] … [from USER]

Chapter 30

About Retaining Mutable Values in Application Continuity for Java

30-18

For example, for EBS standard usage with original dates

Grant KEEP DATE TIME, KEEP SYSGUID to [custom user];

Grant KEEP DATE TIME, KEEP SYSGUID to [apps user];

30.9.1.2 Sequence Syntax

The Sequence syntax can be of the following types:

• Owned Sequence Syntax

• Others Sequence Syntax

Owned Sequence Syntax

ALTER SEQUENCE [sequence object] [KEEP|NOKEEP];

This command retains the original values of

sequence.nextval

for replaying, so that the keys

match after replay. Most applications need to retain the sequence values at replay. The

ALTER

SYNTAX

is only for owned sequences.

Others Sequence Syntax

GRANT KEEP SEQUENCE..[to USER] on [sequence object];

REVOKE KEEP SEQUENCE … [from USER] on [sequence object];

For example, use the following command for EBS standard usage with original sequence

values:

Grant KEEP SEQUENCE to [apps user] on [sequence object];

Grant KEEP SEQUENCE to [custom user] on [sequence object];

30.9.1.3 GRANT ALL Statement

The

GRANT ALL

statement grants

KEEP

privilege on all the objects of a user. However, it

excludes mutable values, that is, mutable values require explicit grants.

30.9.1.4 Rules for Grants on Mutable Values

Follow these rules while granting privileges on mutable objects:

• If a user has

KEEP

privilege granted on mutables values, then the objects inherit mutable

access when the

SYS_GUID

SYSDATE

, and

SYSTIMESTAMP

functions are called.

• If the

KEEP

privilege on mutable values on a sequence object is revoked, then SQL or

PL/SQL blocks using that object will not allow mutable collection or application for that

sequence.

• If granted privileges are revoked between runtime and failover, then the mutable values

that are collected are not applied for replay.

• If new privileges are granted between runtime and failover, mutable values are not

collected and these values are not applied for replay.

Chapter 30

About Retaining Mutable Values in Application Continuity for Java

30-19

30.10 Application Continuity Statistics

The JDBC Replay Data Source supports the following statistics for an application

using Application Continuity:

• Total number of requests

• Total number of completed requests

• Total number of calls

• Total number of protected calls

• Total number of calls affected by outages

• Total number of calls triggering replay

• Total number of calls affected by outages during replay

• Total number of successful replay

• Total number of failed replay

• Total number of disabled replay

• Total number of replay attempts

All these metrics are available both on a per-connection basis and across-connections

basis. You can use the following methods for obtaining these statistics:

•

getReplayStatistics(StatisticsReportType)

Use the

oracle.jdbc.replay.ReplayableConnection.getReplayStatistics(Statistics

ReportType)

method to obtain the snapshot statistics. The argument to this

method is an enum type also defined in the same

ReplayableConnection

interface. To obtain statistics across connections, it is best calling this method after

the main application logic. Applications can either use any

oracle.jdbc.replay.ReplayableConnection

that is still open, or open a new

connection to the same data source. This applies to applications using both UCP

and WLS data sources, and applications that directly use the replay data source.

•

getReplayStatistics()

Use the

oracle.jdbc.replay.OracleDataSource.getReplayStatistics()

method to obtain across-connection statistics. This applies only to applications that

directly use replay data source.

Both methods return an

oracle.jdbc.replay.ReplayStatistics

object, from which

you can retrieve individual replay metrics. The following is a sample output that prints

a ReplayStatistics object as String:

AC Statistics:

===============================================

TotalRequests = 1

TotalCompletedRequests = 1

TotalCalls = 19

TotalProtectedCalls = 19

===============================================

TotalCallsAffectedByOutages = 3

Chapter 30

Application Continuity Statistics

30-20

TotalCallsTriggeringReplay = 3

TotalCallsAffectedByOutagesDuringReplay = 0

===============================================

SuccessfulReplayCount = 3

FailedReplayCount = 0

ReplayDisablingCount = 0

TotalReplayAttempts = 3

===============================================

If you want to clear the accumulated replay statistics per connection or for all connections,

then you can use the following methods:

•

oracle.jdbc.replay.ReplayableConnection.clearReplayStatistics(ReplayableConn

ection.StatisticsReportType reportType)

•

oracle.jdbc.replay.OracleDataSource.clearReplayStatistics()

Note:

All statistics reflect only updates since the latest clearing.

30.11 About Disabling Replay in Application Continuity for Java

This section describes the following concepts:

• How to Disable Replay

• When to Disable Replay

• Diagnostics and Tracing

30.11.1 How to Disable Replay

If any application module uses a design that is unsuitable for replay, then the disable replay

API disables replay on a per request basis. Disabling replay can be added to the callback or

to the main code by using the

disableReplay

method of the

oracle.jdbc.replay.ReplayableConnection

interface. For example:

if (connection instanceof oracle.jdbc.replay.ReplayableConnection)

{

(( oracle.jdbc.replay.ReplayableConnection)connection).disableReplay();

}

Disabling replay does not alter the connection state by reexecuting any JDBC method, SQL

or PL/SQL. When replay is disabled using the disable replay API, both recording and replay

are disabled until that request ends. There is no API to reenable replay because it is invalid to

reestablish the database session with time gaps in a replayed request. This ensures that

replay runs only if a complete history of needed calls has been recorded.

Chapter 30

About Disabling Replay in Application Continuity for Java

30-21

30.11.2 When to Disable Replay

By default, the JDBC Replay Data Source replays following a recoverable error. The

disable replay API can be used in the entry point of application modules that are

unable to lose the database sessions and recover. For example, if the application uses

the

UTL_SMTP

package and does not want messages to be repeated, then the

disableReplay

API affects only the request that needs to be disabled. All other

requests continue to be replayed.

The following are scenarios to consider before configuring an application for replay:

• Application Calls External PL/SQL Actions that Should not Be Repeated

• Application Synchronizes Independent Sessions

• Application Uses Time at the Middle-tier in the Execution Logic

• Application assumes that ROWIds do not change

• Application Assumes that Side Effects Execute Once

• Application Assumes that Location Values Do not Change

30.11.2.1 Application Calls External Systems that Should not Be Repeated

During replay, autonomous transactions and external systems (like PL/SQL calls or

Java calls) can have side effects that are separate from the main transaction. These

side effects are replayed unless you specify otherwise and leave persistent results

behind. These side effects include writing to an external table, sending email, forking

sessions out of PL/SQL or Java, transferring files, accessing external URLs, and so

on. For example, in case of PL/SQL messaging, suppose, you walk away in-between

some work without committing and the session times out. Now, if you issue a

Ctrl+C

command, then the foreground of a component fails. When you resubmit the work,

then this side effect can also be repeated.

See Also:

Oracle Real Application Clusters Administration and Deployment Guide for

more information about potential side effects of Application Continuity

You must make a conscious decision about whether to enable replay for external

actions or not. For example, you can consider the following situations where this

decision is important:

• Using the

UTL_HTTP

package to issue a SOA call

• Using the

UTL_SMTP

package to send a message

• Using the

UTL_URL

package to access a web site

Use the

disableReplay

API if you do not want such external actions to be replayed.

30.11.2.2 Application Synchronizes Independent Sessions

You can configure an application for replay if the application synchronizes independent

sessions using volatile entities that are held until commit, rollback, or session loss. In

Chapter 30

About Disabling Replay in Application Continuity for Java

30-22

this case, the application synchronizes multiple sessions connected to several data sources

that are otherwise inter-dependent using resources such as a database lock. This

synchronization may be fine if the application is only serializing these sessions and

understands that any session may fail. However, if the application assumes that a lock or any

other volatile resource held by one data source implies exclusive access to data on the same

or a separate data source from other connections, then this assumption may be invalidated

when replaying.

During replay, the driver is not aware that the sessions are dependent on one session holding

a lock or other volatile resource. You can also use pipes, buffered queues, stored procedures

taking a resource (such as a semaphore, device, or socket) to implement the synchronization

that are lost by failures.

Note:

The

DBMS_LOCK

does not replay in the restricted version.

30.11.2.3 Application Uses Time at the Middle-tier in the Execution Logic

In this case, the application uses the wall clock at the middle-tier as part of the execution

logic. The JDBC Replay Data Source does not repeat the middle-tier time logic, but uses the

database calls that execute as part of this logic. For example, an application using middle-tier

time may assume that a statement executed at Time T1 is not reexecuted at Time T2, unless

the application explicitly does so.

30.11.2.4 Application assumes that ROWIds do not change

If an application caches ROWIDs, then access to these ROWIDs may be invalidated due to

database changes. Although a ROWID uniquely identifies a row in a table, a ROWID may

change its value in the following situations:

• The underlying table is reorganized

• An index is created on the table

• The underlying table is partitioned

• The underlying table is migrated

• The underlying table is exported and imported using EXP/IMP/DUL

• The underlying table is rebuilt using Golden Gate or Logical Standby or other replication

technology

• The database of the underlying table is flashed back or restored

It is bad practice for an application to store ROWIDs for later use as the corresponding row

may either not exist or contain completely different data.

30.11.2.5 Application Assumes that Side Effects Execute Once

In this case, the following are replayed during a replay:

• Autonomous transactions

• Opening of back channels separate to the main transaction side effects

Chapter 30

About Disabling Replay in Application Continuity for Java

30-23

Examples of back channels separate to the main transaction include writing to an

external table, sending email, forking sessions out of PL/SQL or Java, writing to output

files, transferring files, and writing exception files. Any of these actions leave persistent

side effects in the absence of replay. Back channels can leave persistent results

behind. For example, if a user leaves a transaction midway without committing and the

session times out, then the user presses Ctrl+C, the foreground or any component

fails. If the user resubmits work, then the side effects can be repeated.

30.11.2.6 Application Assumes that Location Values Do not Change

SYSCONTEXT

options comprise a location-independent set such as National Language

Support (NLS) settings,

ISDBA

CLIENT_IDENTIFIER

MODULE

, and

ACTION

, and a

location-dependent set that uses physical locators. Typically, an application does not

use the physical identifier, except in testing environments. If physical locators are used

in mainline code, then the replay finds the mismatch and rejects it. However, it is fine

to use physical locators in callbacks.

Example

select

sys_context('USERENV','DB_NAME')

,sys_context('USERENV','HOST')

,sys_context('USERENV','INSTANCE')

,sys_context('USERENV','IP_ADDRESS')

,sys_context('USERENV','ISDBA')

,sys_context('USERENV','SESSIONID')

,sys_context('USERENV','TERMINAL')

,sys_context('USERENV',ID')

from dual

30.11.3 Diagnostics and Tracing

The JDBC Replay Data Source supports standard JDK logging. Logging is enabled

using the Java command-line

-Djava.util.logging.config.file=<file>

option. Log

level is controlled with the

oracle.jdbc.internal.replay.level

attribute in the log

configuration file. For example:

oracle.jdbc.internal.replay.level = FINER|FINEST

where,

FINER

produces external APIs and

FINEST

produces large volumes of trace.

You must use

FINEST

only under supervision.

If you use the

java.util.logging.XMLFormatter

class to format a log record, then the

logs are more readable but larger. If you are using replay with FAN enabled on UCP or

WebLogic Server, then you should also enable FAN-processing logging.

See Also:

Oracle Universal Connection Pool for JDBC Developer's Guide

30.11.3.1 Writing Replay Trace to Console

Following is the example of a configuration file for logging configuration.

Chapter 30

About Disabling Replay in Application Continuity for Java

30-24

oracle.jdbc.internal.replay.level = FINER

handlers = java.util.logging.ConsoleHandler

java.util.logging.ConsoleHandler.level = ALL

java.util.logging.ConsoleHandler.formatter = java.util.logging.XMLFormatter

30.11.3.2 Writing Replay Trace to a File

Following is the example of a

properties

file for logging configuration.

oracle.jdbc.internal.replay.level = FINEST

# Output File Format (size, number and style)

# count: Number of output files to cycle through, by appending an integer to the base

file name:

# limit: Limiting size of output file in bytes

handlers = java.util.logging.FileHandler

java.util.logging.FileHandler.pattern = [file location]/replay_%U.trc

java.util.logging.FileHandler.limit = 500000000

java.util.logging.FileHandler.count = 1000

java.util.logging.FileHandler.formatter = java.util.logging.XMLFormatter

See Also:

Restrictions and Other Considerations for Application Continuity

Chapter 30

About Disabling Replay in Application Continuity for Java

30-25

Oracle JDBC Support for FAN Events

Starting from Oracle Database 12c Release 2 (12.2.0.1), Oracle JDBC driver supports Oracle

RAC Fast Application Notification (FAN) events, for planned and unplanned outages. This

facilitates third-party connection pools to leverage Oracle RAC features for high availability.

Java applications not using Oracle Universal Connection Pool (UCP) or WebLogic Server can

now leverage on this support. For example, scenarios like rolling upgrades at the Oracle RAC

server-side do not cause JDBC errors within applications.

Note:

Although the Oracle JDBC drivers now support the FAN events, Oracle UCP

provides more comprehensive support for all FAN events.

See Also:

Oracle Universal Connection Pool Developer’s Guide

• Overview of Oracle JDBC Support for FAN events

• Safe Draining APIs for Planned Maintenance

• Installation and Configuration of Oracle JDBC Driver for FAN Events Support

31.1 Overview of Oracle JDBC Support for FAN events

You must use an Oracle RAC Database or an Oracle Restart on a single instance database

to use this feature.

This feature supports:

• Planned maintenance

This case deals with planned maintenance on Oracle RAC servers, where an Oracle

RAC service can be gracefully shutdown. In this case, borrowed or in-use connections

from a connection pool are not interrupted, and are closed only until any safe-draining

API is invoked. For example, when an application completes work on such a connection

and returns it to the connection pool.

• Unplanned outages

In this case, dead connections are rapidly detected and terminated, so that the network

connections to the server do not become nonresponsive.. In this case, borrowed and in-

use connections are interrupted during unplanned outages. Applications are expected to

handle any exception on affected connections and perform necessary recovery, either on

their own, or using Oracle high-availability solutions such as Application Continuity.

31-1

Related Topics

• Application Continuity for Java

Related Topics

• Safe Draining APIs for Planned Maintenance

See Also:

Oracle Real Application Clusters Administration and Deployment Guidefor

server-side configuration about using Oracle RAC. This chapter describes

only the client-side configuration steps that an application must perform

when using Oracle JDBC driver support for FAN events.

31.2 Safe Draining APIs for Planned Maintenance

For planned Oracle RAC maintenance, the JDBC driver supports a list of safe-draining

APIs, which are required for additional handshake or integration work with a third-party

Java connection pool. These APIs serve as the draining-points, where the driver can

safely close any connection affected by a planned maintenance, without causing

application-visible errors. Following is the list of safe-draining APIs that driver FAN

supports:

•

java.sql.Connection.isValid(int timeout)

•

oracle.jdbc.OracleConnection.pingDatabase()

•

oracle.jdbc.OracleConnection.pingDatabase(int timeout)

•

oracle.jdbc.OracleConnection.endRequest()

• All standard JDBC and Oracle JDBC extension

EXECUTE***

calls on

Statement

PreparedStatement

, and

CallableStatement

interfaces

For the standard JDBC and Oracle JDBC extension

EXECUTE***

calls, the executed

SQL command string must contain the following SQL hint as the first noncomment

token within the SQL string:

/*+ CLIENT_CONNECTION_VALIDATION */

Qualified SQLs are treated as connection-validation SQLs. For example:

/*+ CLIENT_CONNECTION_VALIDATION */ SELECT 1 FROM DUAL

Typically, a third-party connection pool places calls to these APIs. It is expected that on

detection of any bad connection with such invocations, a third-party connection pool

closes and removes the related connection from the pool, so that no errors are visible

to applications. When the application itself calls these APIs, then it is expected that

application is actively validating the underlying connection and will close and remove

any bad connection detected.

Chapter 31

Safe Draining APIs for Planned Maintenance

31-2

31.3 Installation and Configuration of Oracle JDBC Driver for

FAN Events Support

Oracle JDBC driver automatically determines whether to enable Oracle JDBC support for

FAN events, by checking the database server that it connects to, and whether the following

necessary JAR files are available in the application environment, in addition to the Oracle

JDBC driver or not:

• The

simplefan.jar

and

ons.jar

files

You must install the 12.2.0.1 version of the

simplefan.jar

and

ons.jar

files from the

following link and include them in the

CLASSPATH

JDBC and UCP Downloads page

If either one is missing, or the driver is unable to load it, then this feature is disabled.

When used with a third-party connection pool, these JAR files must be placed in the

same location, where the connection pool retrieves and loads the driver JAR files.

• Oracle JDBC data sources

You can use the same typical Oracle JDBC data sources, such as

oracle.jdbc.pool.OracleDataSource

oracle.jdbc.OracleDriver

for obtaining JDBC

connections. When used together with a third-party connection pool, your application

must specify these classes as connection factories for the connection pool.

Applications that want to explicitly disable this feature, can set the

oracle.jdbc.fanEnabled

property to

FALSE

. This property is available as both a system property and a connection

property. For applications using Universal Connection Pool (UCP) or WebLogic Server Active

GridLink (AGL), this property is set to

FALSE

by default. Otherwise, the default value is

TRUE

Note:

• When the JDBC driver automatically enables support for FAN events, with both

the

simplefan.jar

and the

ons.jar

files present on the

CLASSPATH

, then calling

the

getConnection

method may throw an exception, such as,

java.lang.IllegalArgumentException

. To avoid this, you can perform either of

the following:

– Remove either

simplefan.jar

ons.jar

from the

CLASSPATH

– Set the

oracle.jdbc.fanEnabled

property to

FALSE

to disable this feature

explicitly.

• Setting the

oracle.jdbc.fanEnabled

property to

TRUE

may not enable Oracle

JDBC Support for FAN Events feature as the feature depends on other factors

too.

The JDBC driver requires minimal configuration changes or code changes to a third-party

connection pool for supporting Oracle FAN events. For a connection pool that does not need

any configuration change or code change, it is assumed that it fulfils one of the following

criteria:

Chapter 31

Installation and Configuration of Oracle JDBC Driver for FAN Events Support

31-3

• The pool has a configuration option for validating JDBC connections at pool

checkout time.

• The pool uses

javax.sql.PooledConnection

and has a configuration option for

plugging in a

javax.sql.ConnectionPoolDataSource

implementation. Such a

connection pool is also assumed to be able to check for closed or bad physical

connections at connection returns.

Following are a few connection validation options on some third-party Java connection

pools. The majority of these options are based on SQL, and not on validation APIs:

Java Connection Pool Connection Validation Options

Oracle WebLogic Generic and MDS data

sources

TestConnectionsOnReserve

TestConnectionsOnRelease

TestConnectionsOnCreate

IBM WebSphere

PreTest

Connection

RedHat JBoss

check-valid-connection-sql

Apache TomCat

TestonBorrow

TestonRelease

When you use Oracle JDBC support for FAN events feature with an Oracle RAC

server Release 11g, then applications must explicitly set the remote ONS configuration

string for Oracle RAC FAN through the

oracle.jdbc.fanONSConfig

system property.

The value and the format of the property are the same as for UCP Fast Connection

Failover (FCF).

See Also:

Universal Connection Pool Developer’s Guide

31.4 Example of Oracle JDBC Driver FAN support for

Planned Maintenance

The following example illustrates how you can typically enable and use JDBC Oracle

FAN support with planned maintenance on Oracle RAC. Applications should not

receive any exception during a planned maintenance after following these instructions:

1. Upgrade Oracle JDBC driver to Release 12.2.0.1 to use the

ojdbc8.jar

file.

2. Install and use the 12.2.0.1 version of the

ons.jar

and

simplefan.jar

files.

3. Use the

oracle.jdbc.pool.OracleDataSource

class to obtain physical

connections or configure this class as the connection factory on a third-party Java

connection pool. In the latter case, you must set the specific pool property that

enables connection validation.

Optionally, when running against Oracle RAC Release 11g, specify the system

property

oracle.jdbc.fanONSConfig

to configure remote ONS.

4. The application runs until you are ready to perform planned maintenance activities

like a rolling upgrade on the Oracle RAC. During the planned maintenance, for

Chapter 31

Example of Oracle JDBC Driver FAN support for Planned Maintenance

31-4

each service based on usage patterns, a DBA will perform the following activities using

the extended 12.2

srvctl

interface:

• Relocate or stop the services on the next instance to upgrade, with no

–f

(force)

• Wait until all connections to this service are drained by driver FAN

• When the timeout is reached, disconnect the sessions with the defined stop mode

(transactional is recommended)

• When all services are relocated or stopped, shutdown the instance and apply the

upgrade or patch

• Restart the instance and restart the services if they were stopped

• Iterate until all instances are upgraded/patched

Chapter 31

Example of Oracle JDBC Driver FAN support for Planned Maintenance

31-5

Transparent Application Failover

This chapter contains the following sections:

• Overview of Transparent Application Failover

• Failover Type Events

• TAF Callbacks

• Java TAF Callback Interface

• Comparison of TAF and Fast Connection Failover

32.1 Overview of Transparent Application Failover

Transparent Application Failover (TAF) is a feature of the Java Database Connectivity (JDBC)

Oracle Call Interface (OCI) driver. It enables the application to automatically reconnect to a

database, if the database instance to which the connection is made fails. In this case, the

active transactions roll back.

When an instance to which a connection is established fails or is shut down, the connection

on the client-side becomes stale and would throw exceptions to the caller trying to use it. TAF

enables the application to transparently reconnect to a preconfigured secondary instance,

creating a fresh connection, but identical to the connection that was established on the first

original instance. That is, the connection properties are the same as that of the earlier

connection. This is true regardless of how the connection was lost.

Note:

• TAF is always active and does not have to be set.

• TAF is not supported with LOB and XML types.

32.2 Failover Type Events

The following are possible failover events in the

OracleOCIFailover

interface:

•

FO_SESSION

Is equivalent to

FAILOVER_MODE=SESSION

in the

tnsnames.ora

file

CONNECT_DATA

flags.

This means that only the user session is authenticated again on the server side, while

open cursors in the OCI application need to be reprocessed.

•

FO_SELECT

Is equivalent to

FAILOVER_MODE=SELECT

tnsnames.ora

file

CONNECT_DATA

flags. This

means that not only the user session is re-authenticated on the server side, but open

cursors in the OCI can continue fetching. This implies that the client-side logic maintains

fetch-state of each open cursor.

32-1

•

FO_NONE

Is equivalent to

FAILOVER_MODE=NONE

in the

tnsnames.ora

file

CONNECT_DATA

flags.

This is the default, in which no failover functionality is used. This can also be

explicitly specified to prevent failover from happening. Additionally,

FO_TYPE_UNKNOWN

implies that a bad failover type was returned from the OCI driver.

•

FO_BEGIN

Indicates that failover has detected a lost connection and failover is starting.

•

FO_END

Indicates successful completion of failover.

•

FO_ABORT

Indicates that failover was unsuccessful and there is no option of retrying.

•

FO_REAUTH

Indicates that a user handle has been re-authenticated.

•

FO_ERROR

Indicates that failover was temporarily unsuccessful, but it gives the application the

opportunity to handle the error and retry failover. The usual method of error

handling is to issue the

sleep

method and retry by returning the value

FO_RETRY

•

FO_RETRY

Indicates that the application should retry failover.

•

FO_EVENT_UNKNOWN

Indicates a bad failover event.

32.3 TAF Callbacks

TAF callbacks are used in the event of the failure of one database connection, and

failover to another database connection. TAF callbacks are callbacks that are

registered in case of failover. The callback is called during the failover to notify the

JDBC application of events generated. The application also has some control of

failover.

Note:

The callback setting is optional.

32.4 Java TAF Callback Interface

The

OracleOCIFailover

interface includes the

callbackFn

method, supporting the

following types and events:

public interface OracleOCIFailover{

// Possible Failover Types

public static final int FO_SESSION = 1;

Chapter 32

TAF Callbacks

32-2

public static final int FO_SELECT = 2;

public static final int FO_NONE = 3;

public static final int;

// Possible Failover events registered with callback

public static final int FO_BEGIN = 1;

public static final int FO_END = 2;

public static final int FO_ABORT = 3;

public static final int FO_REAUTH = 4;

public static final int FO_ERROR = 5;

public static final int FO_RETRY = 6;

public static final int FO_EVENT_UNKNOWN = 7;

public int callbackFn (Connection conn,

Object ctxt, // ANy thing the user wants to save

int type, // One of the possible Failover Types

int event ); // One of the possible Failover Events

Handling the FO_ERROR Event

In case of an error while failing over to a new connection, the JDBC application is able to

retry failover. Typically, the application sleeps for a while and then it retries, either indefinitely

or for a limited amount of time, by having the callback return

FO_RETRY

Handling the FO_ABORT Event

Callback registered should return the

FO_ABORT

event if the

FO_ERROR

event is passed to it.

32.5 Comparison of TAF and Fast Connection Failover

Transparent Application Failover (TAF) differs from Fast Connection Failover in the following

ways:

• Application-level connection retries

TAF supports connection retries only at the OCI/Net layer. Fast Connection Failover

supports application-level connection retries. This gives the application control of

responding to connection failovers. The application can choose whether to retry the

connection or to rethrow the exception.

• Integration with the Universal Connection Pool

TAF works at the network level on a per-connection basis, which means that the

connection cache cannot be notified of failures. Fast Connection Failover is well-

integrated with the Universal Connection Pool, which enables the Connection Cache

Manager to manage the cache for high availability. For example, failed connections are

automatically invalidated in the cache.

• Event-based

Fast Connection Failover is based on the Oracle RAC event mechanism. This means that

Fast Connection Failover is efficient and detects failures quickly for both active and

inactive connections.

• Load-balancing support

Fast Connection Failover supports

event load balancing of connections and run-time

work request distribution across active Oracle RAC instances.

Chapter 32

Comparison of TAF and Fast Connection Failover

32-3

See Also:

Oracle Universal Connection Pool for JDBC Developer's Guide

Note:

Oracle recommends not to use TAF and Fast Connection Failover in the

same application.

Chapter 32

Comparison of TAF and Fast Connection Failover

32-4

Single Client Access Name

Single Client Access Name (SCAN) is an Oracle Real Application Clusters (Oracle RAC)

feature that provides a single name for clients to access Oracle Databases running in a

cluster. This chapter discusses the following concepts related to the SCAN:

• Overview of Single Client Access Name

• About Configuring the Database Using the SCAN

• Using the SCAN in a Maximum Availability Architecture Environment

• Using the SCAN With Oracle Connection Manager

33.1 Overview of Single Client Access Name

The SCAN is a domain name registered to at least one and up to three IP addresses, either

in Domain Naming Service (DNS) or Grid Naming Service (GNS). When you use GNS and

Dynamic Host Configuration Protocol (DHCP), Oracle Clusterware configures the Virtual IP

(VIP) addresses for the SCAN name that is provided during cluster configuration. The node

VIP and the three SCAN VIPs are obtained from the DHCP server when you use GNS.

See Also:

Oracle Clusterware Administration and Deployment Guide for more information

about GNS

If a new server joins the cluster, then Oracle Clusterware dynamically obtains the required

VIP address from the DHCP server, updates the cluster resource, and makes the server

accessible through GNS. The benefit of using the SCAN is that the connection information of

the client does not need to change if you add or remove nodes in the cluster. Having a single

name to access the cluster enables the client to use the EZConnect client and the simple

JDBC thin URL to access any Database running in the cluster, independent of the active

servers in the cluster. The SCAN provides load balancing and failover for client connections

to the Database. The SCAN works as a cluster alias for Databases in the cluster.

33.2 About Configuring the Database Using the SCAN

The SCAN is an essential part of Database configuration. So, by default, the

REMOTE_LISTENER

parameter is set to the SCAN, assuming that the Database is created using

standard Oracle tools. This enables the instances to register with the SCAN Listeners as

remote listeners to provide information on what services are being provided by the instance,

the current load, and a recommendation on how many incoming connections should be

directed to the instance.

In this context, you must set the

LOCAL_LISTENER

parameter to the node-VIP. If you need fully

qualified domain names, then ensure that the

LOCAL_LISTENER

parameter is set to the fully

33-1

qualified domain name. By default, a node listener is created on each node in the

cluster during cluster configuration. With Oracle Grid Infrastructure, the node listener

runs out of the Oracle Grid Infrastructure home and listens on the node-VIP using the

specified port. The default port is 1521.

Unlike in earlier Database versions, Oracle does not recommend to set your

REMOTE_LISTENER

parameter to a server side

TNSNAMES

alias that resolves the host to

the SCAN in the address list entry, for example,

HOST=sales1-scan

. Instead, you must

use the simplified

SCAN:port

syntax as shown in the following table that shows typical

setting for a

LOCAL_LISTENER

and

REMOTE_LISTENER

Name Type Value

LOCAL_LISTENER

string

(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(

PROTOCOL=TCP)(HOST=localhost)

(PORT=5221))))

REMOTE_LISTENER

string

example.us.oracle.com:5221

Note:

If you are using the easy connect naming method, you may need to modify

the

SQLNET.ORA

file to ensure that

EZCONNECT

is in the list when you specify

the order of the naming methods used for the client name resolution lookups.

33.3 How Connection Load Balancing Works Using the

SCAN

For clients connecting using Oracle SQL*Net, three IP addresses are received by the

client by resolving the SCAN name through DNS. The client then goes through the list

that it receives from the DNS and tries connecting through one of the IP addresses in

the list. If the client receives an error, then it tries connecting to the other addresses

before returning an error to the user or application. This is similar to how client

connection failover works in earlier Database releases, when an address list is

provided in the client connection string.

When a SCAN Listener receives a connection request, the SCAN Listener checks for

the least loaded instance providing the requested service. It then re-directs the

connection request to the local listener on the node where the least loaded instance is

running. Subsequently, the client is given the address of the local listener. The local

listener then finally creates the connection to the Database instance.

Chapter 33

How Connection Load Balancing Works Using the SCAN

33-2

Figure 33-1 Connection Load Balancing Using the SCAN

Example

This example assumes an Oracle client using a default

TNSNAMES.ora

file:

ORCLservice =(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST = sales1-scan.example.com)

(PORT = 1521))(CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = MyORCLservice)))

33.4 Version and Backward Compatibility

To successfully use the SCAN to connect to an Oracle RAC Database in the cluster depends

on the following two factors:

• Ability of the client to understand and use the SCAN

Chapter 33

Version and Backward Compatibility

33-3

• The correct configuration of the

REMOTE_LISTENER

parameter setting in the

Database

If the version of the Oracle Client connecting to the Database and the Oracle

Database version used are both Oracle Database 11g Release 2, and the default

configuration is used as described in the preceding sections, then typically you do not

need to make any change to the system.

If both the Oracle Client version and the version of the Oracle Database that the client

is connecting to are earlier than Oracle Database 11g Release 2, then typically you do

not need to make any change to the system. In this case, the client uses a TNS

connect descriptor that resolves to the node-VIPs of the cluster, while Oracle

Database uses a

REMOTE_LISTENER

entry pointing to the node-VIPs. The disadvantage

of this configuration is that the SCAN is not used and therefore every time the cluster

changes in the back end, the clients are exposed to changes.

If you are using Oracle Database 11g Release 2, but the clients are on an earlier

version of the Database, then you must change the Oracle client, or the Oracle

Database

REMOTE_LISTENER

parameter settings, or both accordingly. You must

consider the following cases in such a scenario:

Table 33-1 Oracle Client and Oracle Database Version Compatibility for the

SCAN

Oracle Client Version Oracle Database Version Comment

Oracle Database 11g Release

No change is required

Oracle Database 11g Release

Oracle Database Version

earlier than Oracle Database

11g Release 2

Add the SCAN VIPs as hosts

to the

REMOTE_LISTENER

parameter.

Oracle Database Version

earlier than Oracle Database

11g Release 2

Oracle Database 11g Release

Update the client

TNSNAMES.ora

file to include

the SCAN VIPs. If the

Database is upgraded using

the Database Upgrade

Assistant (DBUA) from a

Database earlier than 11g

Release 2, then the DBUA

configures the

REMOTE_LISTENER

parameter

to point to the node-VIPs and

the SCAN.

Oracle Database Version

earlier than Oracle Database

11g Release 2

Oracle Database Version

earlier than Oracle Database

11g Release 2

If you want to make use of the

SCAN (recommended), then

add the SCAN VIPs as hosts

to the

REMOTE_LISTENER

parameter and update the

client

TNSNAMES.ora

file to

include the SCAN VIPs.

Otherwise, no change

required.

If you are using a client earlier than Oracle Database 11g Release 2, then you cannot

fully benefit from the advantages of the SCAN because the Oracle Client cannot

handle a set of three IP addresses returned by the DNS for the SCAN. Instead, it tries

to connect to only the first address returned in the list and ignores the other two

Chapter 33

Version and Backward Compatibility

33-4

addresses. If the SCAN Listener listening on this specific IP address is not available or the IP

address itself is not available, then the connection fails. To ensure load balancing and

connection failover with clients earlier than Oracle Database 11g Release 2, you must update

the

TNSNAMES.ora

file of the client, so that it uses three address lines, where each address

line resolves to one of the SCAN VIPs. The following example shows a sample

TNSNAMES.ora

file for a client earlier than Oracle Database 11g Release 2:

sales.example.com =(DESCRIPTION=

(ADDRESS_LIST= (LOAD_BALANCE=on)(FAILOVER=ON)

(ADDRESS=(PROTOCOL=tcp)(HOST=133.22.67.192)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=133.22.67.193)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=133.22.67.194)(PORT=1521)))

(CONNECT_DATA=(SERVICE_NAME= salesservice.example.com)))

33.5 Using the SCAN in a Maximum Availability Architecture

Environment

If you have a Maximum Availability Architecture (MAA) environment implemented, in which

you use Oracle RAC for both your primary and standby Databases that are synchronized

using Oracle Data Guard, then using the SCAN provides a simplified

TNSNAMES

configuration

that a client can use to connect to the Database, independent of whether the primary or

standby Database is the currently active Database.

To use this simplified configuration, Oracle Database 11g Release 2 introduced the following

two SQL*Net parameters that can be used for connection strings of individual clients:

• The

CONNECT_TIMEOUT

parameter

It specifies the timeout duration in seconds for a client to establish an Oracle Net

connection to an Oracle Database. This parameter overrides the

SQLNET.OUTBOUT_CONNECT_TIMEOUT

parameter in the

SQLNET.ORA

file.

• The

RETRY_COUNT

parameter

It specifies the number of times an

ADDRESS_LIST

is traversed before the connection

attempt is terminated.

Using these two parameters, both the SCANs, the one on the primary site and the one on the

standby site, can be used in the client connection strings. Also, if the randomly selected

address points to the site that is not currently active, then the timeout enables the connection

request to failover before the client waits for an unreasonably long time. The following

example shows a sample

TNSNAMES.ORA

entry for a MAA environment:

sales.example.com =(DESCRIPTION= (CONNECT_TIMEOUT=10)(RETRY_COUNT=3)

(ADDRESS_LIST= (LOAD_BALANCE=on)(FAILOVER=ON)

(ADDRESS=(PROTOCOL=tcp)(HOST=sales1-scan)(PORT=1521))

(ADDRESS=(PROTOCOL=tcp)(HOST=sales2-scan)(PORT=1521)))

(CONNECT_DATA=(SERVICE_NAME= salesservice.example.com)))

33.6 Using the SCAN With Oracle Connection Manager

If you use Oracle Connection Manager (CMAN) with your Oracle RAC Database, then the

REMOTE_LISTENER

parameter for the Oracle RAC instances must include the CMAN server, so

that the CMAN server receives load balancing related information and can load balance

connections across the available instances. The easiest way to achieve this is to add the

CMAN server as an entry to the

REMOTE_LISTENER

parameter of the Databases that clients

Chapter 33

Using the SCAN in a Maximum Availability Architecture Environment

33-5

want to connect to through CMAN. You must also remove the SCAN from the

TNSNAMES

connect descriptor of the clients and configure the CMAN server. The

following example shows a server-side

TNSNAMES.ora

example entry when you use

CMAN:

SQL> show parameters listener

NAME TYPE VALUE

-------------------------- ----------- ------------------------------

listener_networks string

local_listener string (DESCRIPTION=(ADDRESS_LIST=

(ADDRESS=(PROTOCOL=TCP)

(HOST=148.87.58.109)(PORT=1521))))

remote_listener string stscan3.oracle.com:1521,(DESCRIPTION=

(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)

(HOST=CMANserver)(PORT=1521))))

See Also:

Oracle Database Net Services Reference for more information about

configuring the CMAN server

Chapter 33

Using the SCAN With Oracle Connection Manager

33-6

Part VII

Transaction Management

This part provides information about transaction management in Oracle Java Database

Connectivity (JDBC). It includes a chapter that discusses the Oracle JDBC implementation of

distributed transactions.

Part VII contains the following chapter:

• Distributed Transactions

Distributed Transactions

This chapter discusses the Oracle Java Database Connectivity (JDBC) implementation of

distributed transactions. These are multiphased transactions, often using multiple databases,

which must be committed in a coordinated way. There is also related discussion of XA, which

is a general standard, and not specific to Java, for distributed transactions.

The following topics are discussed:

• AboutDistributed Transactions

• XA Components

• Error Handling and Optimizations

• About Implementing a Distributed Transaction

• Native-XA in Oracle JDBC Drivers

Note:

This chapter discusses features of the JDBC 2.0 Optional Package, formerly known

as the JDBC 2.0 Standard Extension application programming interface (API) that is

available through the

javax

packages.

For further introductory and general information about distributed transactions, refer to the

specifications for the JDBC 2.0 Optional Package and the Java Transaction API (JTA).

34.1 About Distributed Transactions

The section covers the following topics:

• Overview of Distributed Transaction

• Distributed Transaction Components and Scenarios

• Distributed Transaction Concepts

• About Switching Between Global and Local Transactions

• Oracle XA Packages

34.1.1 Overview of Distributed Transaction

A distributed transaction, sometimes referred to as a global transaction, is a set of two or

more related transactions that must be managed in a coordinated way. The transactions that

constitute a distributed transaction might be in the same database, but more typically are in

different databases and often in different locations. Each individual transaction of a distributed

transaction is referred to as a transaction branch.

34-1

For example, a distributed transaction might consist of money being transferred from

an account in one bank to an account in another bank. You would not want either

transaction committed without assurance that both will complete successfully.

In JDBC, distributed transaction functionality is built on top of connection pooling

functionality. This distributed transaction functionality is also built upon the open XA

standard for distributed transactions. XA is part of the X/Open standard and is not

specific to Java.

JDBC is used to connect to database resources. However, to include all changes to

multiple databases within a transaction, you must use the JDBC connections within a

JTA global transaction. The process of including database SQL updates within a

transaction is referred to as enlisting a database resource.

34.1.2 Distributed Transaction Components and Scenarios

In reading the remainder of the distributed transactions section, it will be helpful to

keep the following points in mind:

• A distributed transaction system typically relies on an external transaction

manager, such as a software component that implements standard JTA

functionality, to coordinate the individual transactions.

Many vendors offer XA-compliant JTA modules, including Oracle, which includes

JTA in Oracle9i Application Server and Oracle Application Server 10g.

• XA functionality is usually isolated from a client application, being implemented

instead in a middle-tier environment, such as an application server.

In many scenarios, the application server and transaction manager will be together

on the middle tier, possibly together with some of the application code as well.

• Discussion throughout this section is intended mostly for middle-tier developers.

• The term resource manager is often used in discussing distributed transactions. A

resource manager is simply an entity that manages data or some other kind of

resource. Wherever the term is used in this chapter, it refers to a database.

Note:

Using JTA functionality requires

jta.jar

to be in the

CLASSPATH

environment variable. This file is located at

ORACLE_HOME/jlib

. Oracle

includes this file with the JDBC product.

34.1.3 Distributed Transaction Concepts

When you use XA functionality, the transaction manager uses XA resource instances

to prepare and coordinate each transaction branch and then to commit or roll back all

transaction branches appropriately.

XA functionality includes the following key components:

• XA data sources

These are extensions of connection pool data sources and other data sources,

and similar in concept and functionality.

Chapter 34

About Distributed Transactions

34-2

There will be one XA data source instance for each resource manager that will be used in

the distributed transaction. You will typically create XA data source instances in your

middle-tier software.

XA data sources produce XA connections.

• XA connections

These are extensions of pooled connections and similar in concept and functionality. An

XA connection encapsulates a physical database connection. Individual connection

instances are temporary handles to these physical connections.

An XA connection instance corresponds to a single Oracle session, although the session

can be used in sequence by multiple logical connection instances, as with pooled

connection instances.

You will typically get an XA connection instance from an XA data source instance in your

middle-tier software. You can get multiple XA connection instances from a single XA data

source instance if the distributed transaction will involve multiple sessions in the same

database.

XA connections produce

OracleXAResource

instances and JDBC connection instances.

• XA resources

These are used by a transaction manager in coordinating the transaction branches of a

distributed transaction.

You will get one

OracleXAResource

instance from each XA connection instance, typically

in your middle-tier software. There is a one-to-one correlation between

OracleXAResource

instances and XA connection instances. Equivalently, there is a one-

to-one correlation between

OracleXAResource

instances and Oracle sessions.

In a typical scenario, the middle-tier component will hand off

OracleXAResource

instances

to the transaction manager, for use in coordinating distributed transactions.

Each

OracleXAResource

instance corresponds to a single Oracle session. So, there can

be only a single active transaction branch associated with an

OracleXAResource

instance

at any given time. However, there can be additional suspended transaction branches.

Each

OracleXAResource

instance has the functionality to start, end, prepare, commit, or

roll back the operations of the transaction branch running in the session with which the

OracleXAResource

instance is associated.

The prepare step is the first step of a two-phase commit operation. The transaction

manager will issue a

PREPARE

to each

OracleXAResource

instance. Once the transaction

manager sees that the operations of each transaction branch have prepared successfully,

it will issue a

COMMIT

to each

OracleXAResource

instance to commit all the changes.

• Transaction IDs

These are used to identify transaction branches. Each ID includes a transaction branch

ID component and a distributed transaction ID component. This is how a branch is

associated with a distributed transaction. All

OracleXAResource

instances associated with

a given distributed transaction would have a transaction ID that includes the same

distributed transaction ID component.

•

OracleXAResource.ORATRANSLOOSE

Start a loosely coupled transaction with transaction ID

xid

Chapter 34

About Distributed Transactions

34-3

34.1.4 About Switching Between Global and Local Transactions

Applications can share connections between local and global transactions.

Applications can also switch connections between local transactions and global

transactions.

A connection is always in one of the following modes:

•

NO_TXN

No transaction is actively using this connection.

•

LOCAL_TXN

A local transaction with auto-commit turned off or disabled is actively using this

connection.

•

GLOBAL_TXN

A global transaction is actively using this connection.

Each connection switches automatically between these modes depending on the

operations carried out on the connection. A connection is always in

NO_TXN

mode when

it is instantiated.

Note:

The modes are maintained internally by the JDBC drivers in association with

Oracle Database.

Table 34-1 describes the connection mode transition rules.

Table 34-1 Connection Mode Transitions

Current Mode Switches to NO_TXN

When

Switches to

LOCAL_TXN When

Switches to

GLOBAL_TXN When

NO_TXN

NA Auto-commit mode is

false and an Oracle

data manipulation

language (DML)

statement is run.

The

start

method is

called on an

XAResource

obtained

from the

XAconnection

that provided the current

connection.

LOCAL_TXN

Any of the following

happens:

• An Oracle data

definition language

(DDL) statement is

run.

•

commit

is called.

•

rollback

is called,

but without

parameters.

NA The

start

method is

called on an

XAResource

obtained

from the

XAconnection

that provided the current

connection. This feature

is available starting from

Oracle Database 12c

Release 1 (12.1.0.2).

Chapter 34

About Distributed Transactions

34-4

Table 34-1 (Cont.) Connection Mode Transitions

Current Mode Switches to NO_TXN

When

Switches to

LOCAL_TXN When

Switches to

GLOBAL_TXN When

GLOBAL_TXN

Within a global

transaction open on this

connection,

end

is called

on an

XAResource

obtained from the

XAconnection

that

provided this

connection.

NEVER NA

If none of these rules is applicable, then the mode does not change.

Mode Restrictions on Operations

The current connection mode restricts which operations are valid within a transaction.

• In the

LOCAL_TXN

mode, applications must not call

prepare

commit

rollback

forget

, or

end

on an

XAResource

. Doing so causes an

XAException

to be thrown.

• In the

GLOBAL_TXN

mode, applications must not call

commit

rollback

rollback(Savepoint)

setAutoCommit(true)

, or

setSavepoint

on a

java.sql.Connection

, and must not call

OracleSetSavepoint

oracleRollback

on an

oracle.jdbc.OracleConnection

. Doing so causes a

SQLException

to be thrown.

Note:

This mode-restriction error checking is in addition to the standard error

checking on the transaction and savepoint APIs.

34.1.5 Oracle XA Packages

Oracle supplies the following three packages that have classes to implement distributed

transaction functionality according to the XA standard:

•

oracle.jdbc.xa

•

oracle.jdbc.xa.client

•

oracle.jdbc.xa.server

Classes for XA data sources, XA connections, and XA resources are in both the

client

package and the

server

package. An abstract class for each is in the top-level package. The

OracleXid

and

OracleXAException

classes are in the top-level

oracle.jdbc.xa

package,

because their functionality does not depend on where the code is running.

In middle-tier scenarios, you will import

OracleXid

OracleXAException

, and the

oracle.jdbc.xa.client

package.

If you intend your XA code to run in the target Oracle Database, however, you will import the

oracle.jdbc.xa.server

package instead of the

client

package.

Chapter 34

About Distributed Transactions

34-5

If code that will run inside a target database must also access remote databases, then

do not import either package. Instead, you must fully qualify the names of any classes

that you use from the

client

package to access a remote database or from the

server

package to access the local database. Class names are duplicated between

these packages.

34.2 XA Components

This section discusses the XA components, that is, the standard XA interfaces

specified in the JDBC standard, and the Oracle classes that implement them. The

following topics are covered:

• XADatasource Interface and Oracle Implementation

• XAConnection Interface and Oracle Implementation

• XAResource Interface and Oracle Implementation

• OracleXAResource Method Functionality and Input Parameters

• Xid Interface and Oracle Implementation

34.2.1 XADatasource Interface and Oracle Implementation

The

javax.sql.XADataSource

interface outlines standard functionality of XA data

sources, which are factories for XA connections. The overloaded

getXAConnection

method returns an XA connection instance and optionally takes a user name and

password as input:

public interface XADataSource

{

XAConnection getXAConnection() throws SQLException;

XAConnection getXAConnection(String user, String password)

throws SQLException;

...

}

Oracle JDBC implements the

XADataSource

interface with the

OracleXADataSource

class, located both in the

oracle.jdbc.xa.client package

and the

oracle.jdbc.xa.server

package.

The

OracleXADataSource

classes also extend the

OracleConnectionPoolDataSource

class, which extends the

OracleDataSource

class, and therefore, include all the

connection properties.

The

getXAConnection

methods of the

OracleXADataSource

class returns the Oracle

implementation of XA connection instances, which are

OracleXAConnection

instances.

Note:

You can register XA data sources in Java Naming Directory and Interface

(JNDI) using the same naming conventions as discussed previously for

nonpooling data sources.

Chapter 34

XA Components

34-6

See Also:

For information about Fast Connection Failover, refer to Oracle Universal

Connection Pool for JDBC Developer's Guide.

34.2.2 XAConnection Interface and Oracle Implementation

An XA connection instance, as with a pooled connection instance, encapsulates a physical

connection to a database. This would be the database specified in the connection properties

of the XA data source instance that produced the XA connection instance.

Each XA connection instance also has the facility to produce the

OracleXAResource

instance

that will correspond to it for use in coordinating the distributed transaction.

An XA connection instance is an instance of a class that implements the standard

javax.sql.XAConnection

interface:

public interface XAConnection extends PooledConnection

{

javax.jta.xa.XAResource getXAResource() throws SQLException;

}

As you see, the

XAConnection

interface extends the

javax.sql.PooledConnection

interface,

so it also includes the

getConnection

addConnectionEventListener

, and

removeConnectionEventListener

methods.

Oracle JDBC implements the

XAConnection

interface with the

OracleXAConnection

class,

located both in the

oracle.jdbc.xa.client package

and the

oracle.jdbc.xa.server

package.

The

OracleXAConnection

classes also extend the

OraclePooledConnection

class.

The

OracleXAConnection

class

getXAResource

method returns the Oracle implementation of

OracleXAResource

instance, which is an

OracleXAResource

instance. The

getConnection

method returns an

OracleConnection

instance.

A JDBC connection instance returned by an XA connection instance acts as a temporary

handle to the physical connection, as opposed to encapsulating the physical connection. The

physical connection is encapsulated by the XA connection instance. The connection obtained

from an

XAConnection

object behaves exactly like a regular connection, until it participates in

a global transaction. At that time, auto-commit status is set to

false

. After the global

transaction ends, auto-commit status is returned to the value it had before the global

transaction. The default auto-commit status on a connection obtained from

XAConnection

false

in all releases prior to Oracle Database 10g. Starting from Oracle Database 10g, the

default status is

true

Each time an XA connection instance

getConnection

method is called, it returns a new

connection instance that exhibits the default behavior, and closes any previous connection

instance that still exists and had been returned by the same XA connection instance.

However, it is advisable to explicitly close any previous connection instance before opening a

new one.

Calling the

method of an XA connection instance closes the physical connection to the

database. This is typically performed in the middle tier.

Chapter 34

XA Components

34-7

34.2.3 XAResource Interface and Oracle Implementation

The transaction manager uses

OracleXAResource

instances to coordinate all the

transaction branches that constitute a distributed transaction.

Each

OracleXAResource

instance provides the following key functionality, typically

invoked by the transaction manager:

• It associates and disassociates distributed transactions with the transaction branch

operating in the XA connection instance that produced this

OracleXAResource

instance. Essentially, it associates distributed transactions with the physical

connection or session encapsulated by the XA connection instance. This is done

through use of transaction IDs.

• It performs the two-phase commit functionality of a distributed transaction to

ensure that changes are not committed in one transaction branch before there is

assurance that the changes will succeed in all transaction branches.

Note:

– Because there must always be a one-to-one correlation between XA

connection instances and

OracleXAResource

instances, an

OracleXAResource

instance is implicitly closed when the associated

XA connection instance is closed.

– If a transaction is opened by a given

OracleXAResource

instance,

then it must also be closed by the same

OracleXAResource

instance.

OracleXAResource

instance is an instance of a class that implements the standard

javax.transaction.xa.XAResource

interface. Oracle JDBC implements the

XAResource

interface with the

OracleXAResource

class, located both in the

oracle.jdbc.xa.client

package and the

oracle.jdbc.xa.server

package.

Oracle JDBC driver creates and returns an

OracleXAResource

instance whenever the

getXAResource

method of the

OracleXAConnection

class is called, and it is Oracle

JDBC driver that associates an

OracleXAResource

instance with a connection instance

and the transaction branch being run through that connection.

This method is how an

OracleXAResource

instance is associated with a particular

connection and with the transaction branch being run in that connection.

34.2.4 OracleXAResource Method Functionality and Input Parameters

The

OracleXAResource

class has several methods to coordinate a transaction branch

with the distributed transaction with which it is associated. This functionality usually

involves two-phase commit operations.

A transaction manager, receiving

OracleXAResource

instances from a middle-tier

component, such as an application server, typically invokes this functionality.

Each of these methods takes a transaction ID as input, in the form of an

Xid

instance,

which includes a transaction branch ID component and a distributed transaction ID

component. Every transaction branch has a unique transaction ID, but transaction

Chapter 34

XA Components

34-8

branches belonging to the same global transaction have the same global transaction

component as part of their transaction IDs.

start

Starts work on behalf of a transaction branch, associating the transaction branch with a

distributed transaction.

void start(Xid xid, int flags)

The

flags

parameter must be one or more of the following values:

•

XAResource.TMNOFLAGS

Flags the start of a new transaction branch for subsequent operations in the session

associated with this XA resource instance. This branch will have the transaction ID

xid

which is an

OracleXid

instance created by the transaction manager. This will map the

transaction branch to the appropriate distributed transaction.

•

XAResource.TMJOIN

Joins subsequent operations in the session associated with this XA resource instance to

the existing transaction branch specified by

xid

•

XAResource.TMRESUME

Resumes the transaction branch specified by

xid

Note:

A transaction branch can be resumed only if it had been suspended earlier.

•

OracleXAResource.TMPROMOTE

Promotes a local transaction to a global transaction

•

OracleXAResource.ORATMSERIALIZABLE

Starts a serializable transaction with transaction ID

xid

•

OracleXAResource.ORATMREADONLY

Starts a read-only transaction with transaction ID

xid

•

OracleXAResource.ORATMREADWRITE

Starts a read/write transaction with transaction ID

xid

•

OracleXAResource.ORATRANSLOOSE

Starts a loosely coupled transaction with transaction ID

xid

TMNOFLAGS

TMJOIN

TMRESUME

TMPROMOTE

ORATMSERIALIZABLE

ORATMREADONLY

, and

ORATMREADWRITE

are defined as

static

members of the

XAResource

interface and

OracleXAResource

class.

ORATMSERIALIZABLE

ORATMREADONLY

, and

ORATMREADWRITE

are the

isolation-mode flags. The default isolation behavior is

READ COMMITTED

Chapter 34

XA Components

34-9

Note:

• Instead of using the

start

method with

TMRESUME

, the transaction

manager can cast to

OracleXAResource

and use the

resume(Xid xid)

method, an Oracle extension.

• If you use

TMRESUME

, then you must also use

TMNOMIGRATE

, as in

start(xid, XAResource.TMRESUME | OracleXAResource.TMNOMIGRATE)

This prevents the application from receiving the error

ORA 1002: fetch

out of sequence

• If you use the isolation-mode flags incorrectly, then an exception with

code

XAER_INVAL

is raised. Furthermore, you cannot use isolation-mode

flags when resuming a global transaction, because you cannot set the

isolation level of an existing transaction. If you try to use the isolation-

mode flags when resuming a transaction, then an external Oracle

exception with code ORA-24790 is raised.

• In order to avoid

Error ORA 1002: fetch out of sequence

, include the

TMNOMIGRATE

flag as part of the

start

method. For example:

start(xid, XAResource.TMSUSPEND | OracleXAResource.TMNOMIGRATE);

• All the flags defined in

OracleXAResource

are Oracle extensions. When

writing a transaction manager that uses these flags, you should be

mindful of this.

Note that to create an appropriate transaction ID in starting a transaction branch, the

transaction manager must know to which distributed transaction the transaction branch

belongs. The mechanics of this are handled between the middle tier and transaction

manager.

end

Ends work on behalf of the transaction branch specified by

xid

, disassociating the

transaction branch from its distributed transaction.

void end(Xid xid, int flags)

The

flags

parameter can have one of the following values:

•

XAResource.TMSUCCESS

This is to indicate that this transaction branch is known to have succeeded.

•

XAResource.TMFAIL

This is to indicate that this transaction branch is known to have failed.

•

XAResource.TMSUSPEND

This is to suspend the transaction branch specified by

xid

. By suspending

transaction branches, you can have multiple transaction branches in a single

session. Only one can be active at any given time, however. Also, this tends to be

more expensive in terms of resources than having two sessions.

TMSUCCESS

TMFAIL

, and

TMSUSPEND

are defined as static members of the

XAResource

interface and

OracleXAResource

class.

Chapter 34

XA Components

34-10

Note:

• Instead of using the

end

method with

TMSUSPEND

, the transaction manager can

cast to

OracleXAResource

and use the

suspend(Xid xid)

method, an Oracle

extension.

• This XA functionality to suspend a transaction provides a way to switch

between various transactions within a single JDBC connection. You can use the

XA classes to accomplish this, even if you are not in a distributed transaction

environment and would otherwise have no need for the XA classes.

• If you use

TMSUSPEND

, then you must also use

TMNOMIGRATE

, as in

end(xid,

XAResource.TMSUSPEND | OracleXAResource.TMNOMIGRATE)

. This prevents the

application from receiving the error

ORA 1002: fetch out of sequence

• In order to avoid

Error ORA 1002: fetch out of sequence

, include the

TMNOMIGRATE

flag as part of the end method. For example:

end(xid, XAResource.TMSUSPEND | OracleXAResource.TMNOMIGRATE);

• All the flags defined in

OracleXAResource

are Oracle extensions. Any

transaction manager that uses these flags should take heed of this.

prepare

Prepares the changes performed in the transaction branch specified by

xid

. This is the first

phase of a two-phase commit operation, to ensure that the database is accessible and that

the changes can be committed successfully.

int prepare(Xid xid)

This method returns an integer value as follows:

•

XAResource.XA_RDONLY

This is returned if the transaction branch runs only read-only operations such as

SELECT

statements.

•

XAResource.XA_OK

This is returned if the transaction branch runs updates that are all prepared without error.

XA_RDONLY

and

XA_OK

are defined as

static

members of the

XAResource

interface and

OracleXAResource

class.

Chapter 34

XA Components

34-11

Note:

• The

prepare

method sometimes does not return any value if the

transaction branch runs updates and any of them encounters errors

during preparation. In this case, an XA exception is thrown.

• Always call the

end

method on a branch before calling the

prepare

method.

• If there is only one transaction branch in a distributed transaction, then

there is no need to call the

prepare

method. You can call the

OracleXAResource

commit

method without preparing first.

commit

Commits prepared changes in the transaction branch specified by

xid

. This is the

second phase of a two-phase commit and is performed only after all transaction

branches have been successfully prepared.

void commit(Xid xid, boolean onePhase)

Set the

onePhase

parameter as follows:

•

true

This is to use one-phase instead of two-phase protocol in committing the

transaction branch. This is appropriate if there is only one transaction branch in

the distributed transaction; the

prepare

step would be skipped.

•

false

This is to use two-phase protocol in committing the transaction branch.

rollback

Rolls back prepared changes in the transaction branch specified by

xid

void rollback(Xid xid)

forget

Tells the resource manager to forget about a heuristically completed transaction

branch.

public void forget(Xid xid)

recover

The transaction manager calls this method during recovery to obtain the list of

transaction branches that are currently in prepared or heuristically completed states.

public Xid[] recover(int flag)

Chapter 34

XA Components

34-12

Note:

Values for

flag

other than

TMSTARTRSCAN

TMENDRSCAN

, or

TMNOFLAGS

, cause an

exception to be thrown, otherwise

flag

is ignored.

The resource manager returns zero or more

Xid

s for the transaction branches that are

currently in a prepared or heuristically completed state. If an error occurs during the

operation, then the resource manager throws the appropriate

XAException

Note:

The

recover

method requires SELECT privilege on

DBA_PENDING_TRANSACTIONS

and EXECUTE privilege on

SYS.DBMS_XA

in Oracle database server. For database

versions prior to Oracle Database 11g Release 1, where an Oracle patch including

a fix for bug 5945463 is not available, or it is infeasible to apply the patch for the

particular application scenario, the

recover

method requires

SYSBDBA

privilege.

Regular use of

SYSDBA

privilege is a security risk. So, Oracle strongly recommends

that you upgrade your Database or apply the fix for bug 5945463, if you need to use

the

recover

method.

isSameRM

To determine if two

OracleXAResource

instances correspond to the same resource manager,

call the

isSameRM

method from one

OracleXAResource

instance, specifying the other

OracleXAResource

instance as input. In the following example, presume

xares1

and

xares2

are

OracleXAResource

instances:

boolean sameRM = xares1.isSameRM(xares2);

34.2.5 Xid Interface and Oracle Implementation

The transaction manager creates transaction ID instances and uses them in coordinating the

branches of a distributed transaction. Each transaction branch is assigned a unique

transaction ID, which includes the following information:

• Format identifier

A format identifier specifies a Java transaction manager. For example, there could be a

format identifier

orcl

. This field cannot be null. The size of a format identifier is 4 bytes.

• Global transaction identifier

It is also known as a distributed transaction ID component. The size of a global

transaction identifier is 64 bytes.

• Branch qualifier

It is also known as transaction branch ID component. The size of a branch qualifier is 64

bytes.

The 64-byte global transaction identifier value will be identical in the transaction IDs of all

transaction branches belonging to the same distributed transaction. However, the overall

transaction ID is unique for every transaction branch.

Chapter 34

XA Components

34-13

An XA transaction ID instance is an instance of a class that implements the standard

javax.transaction.xa.Xid

interface, which is a Java mapping of the X/Open

transaction identifier XID structure.

Oracle implements this interface with the

OracleXid

class in the

oracle.jdbc.xa

package.

OracleXid

instances are employed only in a transaction manager,

transparent to application programs or an application server.

Note:

Oracle does not require the use of

OracleXid

for

OracleXAResource

calls.

Instead, use any class that implements the

javax.transaction.xa.Xid

interface.

A transaction manager may use the following in creating an

OracleXid

instance:

public OracleXid(int fId, byte gId[], byte bId[]) throws XAException

fId

is an integer value for the format identifier,

gId[]

is a byte array for the global

transaction identifier, and

bId[]

is a byte array for the branch qualifier.

The

Xid

interface specifies the following getter methods:

•

public int getFormatId()

•

public byte[] getGlobalTransactionId()

•

public type[] getBranchQualifier()

34.3 Error Handling and Optimizations

This section focuses on the functionality of XA exceptions and error handling and the

Oracle optimizations in its XA implementation. It covers the following topics:

• XAException Classes and Methods

• Mapping Between Oracle Errors and XA Errors

• XA Error Handling

• Oracle XA Optimizations

The exception and error-handling discussion includes the standard XA exception class

and the Oracle-specific XA exception class, as well as particular XA error codes and

error-handling techniques.

34.3.1 XAException Classes and Methods

XA methods throw XA exceptions, as opposed to general exceptions or

SQLExceptions

. An XA exception is an instance of the standard class

javax.transaction.xa.XAException

or a subclass.

An Oracle XAException is an instance that consists of an Oracle error portion and an

XA error portion. Oracle provides the

oracle.jdbc.xa.OracleXAException

subclasses

Chapter 34

Error Handling and Optimizations

34-14

of the standard

javax.transaction.xa.XAException

class. An

OracleXAException

instance

is constructed using one of the following constructors:

public OracleXAException()

public OracleXAException(int error)

The error value is an error code that combines an Oracle SQL error value and an XA error

value. The JDBC driver determines exactly how to combine the Oracle and XA error values.

The

OracleXAException

class has the following methods:

•

public int getOracleError()

This method returns the Oracle SQL error code pertaining to the exception, a standard

ORA error number or 0 if there is no Oracle SQL error.

•

public int getXAError()

This method returns the XA error code pertaining to the exception. XA error values are

defined in the

javax.transaction.xa.XAException

class.

34.3.2 Mapping Between Oracle Errors and XA Errors

Oracle errors correspond to XA errors in

OracleXAException

instances as documented in

Table 34-2.

Table 34-2 Oracle-XA Error Mapping

Oracle Error Code XA Error Code

ORA 24756 XAException.XAER_NOTA

ORA 24764 XAException.XA_HEURCOM

ORA 24765 XAException.XA_HEURRB

ORA 24766 XAException.XA_HEURMIX

ORA 24767 XAException.XA_RDONLY

ORA 25351 XAException.XA_RETRY

ORA 30006 XAException.XA_RETRY

ORA 24763 XAException.XAER_PROTO

ORA 24769 XAException.XAER_PROTO

ORA 24770 XAException.XAER_PROTO

ORA 24776 XAException.XAER_PROTO

ORA 2056 XAException.XAER_PROTO

ORA 17448 XAException.XAER_PROTO

ORA 24768 XAException.XAER_PROTO

ORA 24775 XAException.XAER_PROTO

ORA 24761 XAException.XA_RBROLLBACK

ORA 2091 XAException.XA_RBROLLBACK

ORA 2092 XAException.XA_RBROLLBACK

ORA 24780 XAException.XAER_RMERR

Chapter 34

Error Handling and Optimizations

34-15

Table 34-2 (Cont.) Oracle-XA Error Mapping

Oracle Error Code XA Error Code

All other

ORA

errors

XAException.XAER_RMFAIL

34.3.3 XA Error Handling

The following code snippet uses the

OracleXAException

class to process an XA

exception:

try {

...

...Perform XA operations...

...

} catch(OracleXAException oxae) {

int oraerr = oxae.getOracleError();

System.out.println("Error " + oraerr);

}

catch(XAException xae)

{...Process generic XA exception...}

In case the XA operations did not throw an Oracle-specific XA exception, the code

drops through to process a generic XA exception.

34.3.4 Oracle XA Optimizations

Oracle JDBC has functionality to improve performance if two or more branches of a

distributed transaction use the same database instance, meaning that the

OracleXAResource

instances associated with these branches are associated with the

same resource manager.

In such a circumstance, the

prepare

method of only one of these

OracleXAResource

instances will return

XA_OK

or will fail. The rest will return

XA_RDONLY

, even if updates

are made. This allows the transaction manager to implicitly join all the transaction

branches and commit or roll back, in case of failure, the joined transaction through the

OracleXAResource

instance that returned

XA_OK

or failed.

The transaction manager can use the

OracleXAResource

class

isSameRM

method to

determine if two

OracleXAResource

instances are using the same resource manager.

This way it can interpret the meaning of

XA_RDONLY

return values.

34.4 About Implementing a Distributed Transaction

This section provides an example of how to implement a distributed transaction using

Oracle XA functionality. This section covers the following topics:

• Summary of Imports for Oracle XA

• Oracle XA Code Sample

34.4.1 Summary of Imports for Oracle XA

You must import the following for Oracle XA functionality:

Chapter 34

About Implementing a Distributed Transaction

34-16

import oracle.jdbc.xa.OracleXid;

import oracle.jdbc.xa.OracleXAException;

import oracle.jdbc.pool.*;

import oracle.jdbc.xa.client.*;

import javax.transaction.xa.*;

The

oracle.jdbc.pool

package has classes for connection pooling functionality, some of

which have XA-related classes as subclasses.

Alternatively, if the code will run inside Oracle Database and access that database for SQL

operations, you must import

oracle.jdbc.xa.server

instead of

oracle.jdbc.xa.client

import oracle.jdbc.xa.server.*;

If your application must access another Oracle Database as part of an XA transaction using

the server-side Thin driver, then your code can use the fully qualified names of the

oracle.xa.client

classes.

The

client

and

server

packages each have versions of the

OracleXADataSource

OracleXAConnection

, and

OracleXAResource

classes. Abstract versions of these three

classes are in the top-level

oracle.jdbc.xa

package.

34.4.2 Oracle XA Code Sample

This example uses a two-phase distributed transaction with two transaction branches, each

to a separate database.

Note that for simplicity, this example combines code that would typically be in a middle tier

with code that would typically be in a transaction manager, such as the

OracleXAResource

method invocations and the creation of transaction IDs.

For brevity, the specifics of creating transaction IDs and performing SQL operations are not

shown here. The complete example is shipped with the product.

This example performs the following sequence:

1. Start transaction branch #1.

2. Start transaction branch #2.

3. Execute DML operations on branch #1.

4. Execute DML operations on branch #2.

5. End transaction branch #1.

6. End transaction branch #2.

7. Prepare branch #1.

8. Prepare branch #2.

9. Commit branch #1.

10. Commit branch #2.

// You need to import the java.sql package to use JDBC

import java.sql.*;

import javax.sql.*;

import oracle.jdbc.*;

import oracle.jdbc.pool.*;

import oracle.jdbc.xa.OracleXid;

import oracle.jdbc.xa.OracleXAException;

Chapter 34

About Implementing a Distributed Transaction

34-17

import oracle.jdbc.xa.client.*;

import javax.transaction.xa.*;

class XA4

{

public static void main (String args [])

throws SQLException

{

try

{

String URL1 = "jdbc:oracle:oci:@";

// You can put a database name after the @ sign in the connection URL.

String URL2 ="jdbc:oracle:thin:@(description=(address=(host=localhost)

(protocol=tcp)(port=5521))

(connect_data=(service_name=orcl)))";

// Create first DataSource and get connection

OracleDataSource ods1 = new OracleDataSource();

ods1.setURL(URL1);

ods1.setUser("HR");

ods1.setPassword("hr");

Connection conna = ods1.getConnection();

// Create second DataSource and get connection

OracleDataSource ods2 = new OracleDataSource();

ods2.setURL(URL2);

ods2.setUser("HR");

ods2.setPassword("hr");

Connection connb = ods2.getConnection();

// Prepare a statement to create the table

Statement stmta = conna.createStatement ();

// Prepare a statement to create the table

Statement stmtb = connb.createStatement ();

try

{

// Drop the test table

stmta.execute ("drop table my_table");

}

catch (SQLException e)

{

// Ignore an error here

}

try

{

// Create a test table

stmta.execute ("create table my_table (col1 int)");

}

catch (SQLException e)

{

// Ignore an error here too

}

try

{

// Drop the test table

stmtb.execute ("drop table my_tab");

}

Chapter 34

About Implementing a Distributed Transaction

34-18

catch (SQLException e)

{

// Ignore an error here

}

try

{

// Create a test table

stmtb.execute ("create table my_tab (col1 char(30))");

}

catch (SQLException e)

{

// Ignore an error here too

}

// Create XADataSource instances and set properties.

OracleXADataSource oxds1 = new OracleXADataSource();

oxds1.setURL("jdbc:oracle:oci:@");

oxds1.setUser("HR");

oxds1.setPassword("hr");

OracleXADataSource oxds2 = new OracleXADataSource();

oxds2.setURL("jdbc:oracle:thin:@(description=(address=(host=localhost)

(protocol=tcp)(port=5521))(connect_data=(service_name=orcl)))");

oxds2.setUser("HR");

oxds2.setPassword("hr");

// Get XA connections to the underlying data sources

XAConnection pc1 = oxds1.getXAConnection();

XAConnection pc2 = oxds2.getXAConnection();

// Get the physical connections

Connection conn1 = pc1.getConnection();

Connection conn2 = pc2.getConnection();

// Get the XA resources

XAResource oxar1 = pc1.getXAResource();

XAResource oxar2 = pc2.getXAResource();

// Create the Xids With the Same Global Ids

Xid xid1 = createXid(1);

Xid xid2 = createXid(2);

// Start the Resources

oxar1.start (xid1, XAResource.TMNOFLAGS);

oxar2.start (xid2, XAResource.TMNOFLAGS);

// Execute SQL operations with conn1 and conn2

doSomeWork1 (conn1);

doSomeWork2 (conn2);

// END both the branches -- IMPORTANT

oxar1.end(xid1, XAResource.TMSUCCESS);

oxar2.end(xid2, XAResource.TMSUCCESS);

// Prepare the RMs

int prp1 = oxar1.prepare (xid1);

int prp2 = oxar2.prepare (xid2);

System.out.println("Return value of prepare 1 is " + prp1);

Chapter 34

About Implementing a Distributed Transaction

34-19

System.out.println("Return value of prepare 2 is " + prp2);

boolean do_commit = true;

if (!((prp1 == XAResource.XA_OK) || (prp1 == XAResource.XA_RDONLY)))

do_commit = false;

if (!((prp2 == XAResource.XA_OK) || (prp2 == XAResource.XA_RDONLY)))

do_commit = false;

System.out.println("do_commit is " + do_commit);

System.out.println("Is oxar1 same as oxar2 ? " + oxar1.isSameRM(oxar2));

if (prp1 == XAResource.XA_OK)

if (do_commit)

oxar1.commit (xid1, false);

else

oxar1.rollback (xid1);

if (prp2 == XAResource.XA_OK)

if (do_commit)

oxar2.commit (xid2, false);

else

oxar2.rollback (xid2);

// Close connections

conn1.close();

conn1 = null;

conn2.close();

conn2 = null;

pc1.close();

pc1 = null;

pc2.close();

pc2 = null;

ResultSet rset = stmta.executeQuery ("select col1 from my_table");

while (rset.next())

System.out.println("Col1 is " + rset.getInt(1));

rset.close();

rset = null;

rset = stmtb.executeQuery ("select col1 from my_tab");

while (rset.next())

System.out.println("Col1 is " + rset.getString(1));

rset.close();

rset = null;

stmta.close();

stmta = null;

stmtb.close();

stmtb = null;

conna.close();

conna = null;

connb.close();

connb = null;

} catch (SQLException sqe)

Chapter 34

About Implementing a Distributed Transaction

34-20

{

sqe.printStackTrace();

} catch (XAException xae)

{

if (xae instanceof OracleXAException) {

System.out.println("XA Error is " +

((OracleXAException)xae).getXAError());

System.out.println("SQL Error is " +

((OracleXAException)xae).getOracleError());

}

static Xid createXid(int bids)

throws XAException

{...Create transaction IDs...}

private static void doSomeWork1 (Connection conn)

throws SQLException

{...Execute SQL operations...}

private static void doSomeWork2 (Connection conn)

throws SQLException

{...Execute SQL operations...}

}

34.5 Native-XA in Oracle JDBC Drivers

In general, XA commands can be sent to the server in the following ways:

• Through non-native APIs

• Through native APIs

There is a huge performance difference between the two methods of sending XA commands

to the server. The use of native APIs provide high performance gains as compared to the use

of non-native APIs.

Prior to Oracle Database 10g, the Thin driver used non-native APIs to send XA commands to

the server because Thin native APIs were not available. The non-native APIs use PL/SQL

procedures, so they have the following disadvantages:

• They require different messages on the wire.

• They cause more round-trips to the database.

• They cause more cursors to remain open.

• They damage statement caching by occupying space in the Statement Cache.

Moreover, the implementation of non-native APIs is in the server. So, in order to solve any

problem in sending XA commands, it requires a server patch. This creates a major issue

because sometimes the patch requires restarting the server.

Starting from Oracle Database 10g, the Thin native APIs are available and are used to send

XA commands, by default. Native APIs are more than 10 times faster than the non-native

ones.

This section covers the following topics:

• OCI Native XA

Chapter 34

Native-XA in Oracle JDBC Drivers

34-21

• Thin Native XA

34.5.1 OCI Native XA

Native XA is enabled through the use of the

tnsEntry

and

nativeXA

properties of the

OracleXADataSource

class.

Note:

Currently, OCI Native XA does not work in a multithreaded environment. The

OCI driver uses the C/XA library of Oracle to support distributed transactions,

which requires that an XAConnection be obtained for each thread before

resuming a global transaction.

Configuration and Installation

On a Solaris or Linux system, you need the

libheteroxa11.so

shared library to enable

the Native XA feature. This library must be installed and available in the search path

for the Native XA feature to work properly.

On a Microsoft Windows system, you need the

heteroxa11.dll

file to enable the

Native XA feature. This file must be installed and available in the Windows DLL path

for the Native XA feature to work properly.

Exception Handling

When using the Native XA feature in distributed transactions, it is recommended that

the application simply check for

XAException

SQLException

, rather than

OracleXAException

OracleSQLException

Note:

The mapping from SQL error codes to standard XA error codes does not

apply to the Native XA feature.

Native XA Code Example

The following portion of code shows how to enable the Native XA feature:

...

// Create a XADataSource instance

OracleXADataSource oxds = new OracleXADataSource();

oxds.setURL(url);

// Set the nativeXA property to use Native XA feature

oxds.setNativeXA(true);

// Set the tnsEntry property to an older DB as required

oxds.setTNSEntryName("ora805");

...

Chapter 34

Native-XA in Oracle JDBC Drivers

34-22

Related Topics

• Features and Properties of Data Sources

• Native XA Messages

34.5.2 Thin Native XA

Like the JDBC OCI driver, the JDBC Thin driver also provides support for Native XA.

However, the JDBC Thin driver provides support for Native XA by default. This is unlike the

case of the JDBC OCI driver in which the support for Native XA is not enabled by default.

You can disable Native XA by calling

setNativeXA(false)

on the XA data source as follows:

...

// Create a XADataSource instance

OracleXADataSource oxds = new OracleXADataSource();

...

// Disabling Native XA

oxds.setNativeXA(false);

...

For example, you may need to disable Native XA as a workaround for a bug in the Native XA

code.

Chapter 34

Native-XA in Oracle JDBC Drivers

34-23

Part VIII

Manageability

This part discusses the database management and diagnosability support in Oracle Java

Database Connectivity (JDBC) drivers.

Part VIII contains the following chapters:

• Database Administration

• Diagnosability in JDBC

• JDBC DMS Metrics

Database Administration

This chapter discusses the database administration methods introduced in Oracle Database

11g Release 1. This chapter contains the following sections:

• Using the Database Administration Methods

• Using the startup Method

• Using the shutdown Method

• A Complete Example

35.1 Using the Database Administration Methods

Starting from Oracle Database 11g Release 1, two JDBC methods,

startup

and

shutdown

has been added in the

oracle.jdbc.OracleConnection

interface, which enable you to start

up and shut down an Oracle Database instance. This is similar to the way you would start up

or shut down a database instance from SQL*Plus.

To use the

startup

and

shutdown

methods, you must:

• Have a dedicated connection to the server. You cannot be connected to a shared server

through a dispatcher.

• Be connected as

SYSDBA

SYSOPER

. To connect as

SYSDBA

SYSOPER

with Oracle JDBC

drivers, you need to set the

INTERNAL_LOGON

connection property accordingly.

To log on as

SYSDBA

with the JDBC Thin driver you must configure the server to use the

password file. For example, to configure

system/manager

to connect as

SYSDBA

with the

JDBC Thin driver, perform the following:

1. From the command line, type:

orapwd file=$ORACLE_HOME/dbs/orapw entries=5

Enter password: password

2. Connect to database as

SYSDBA

and run the following commands from SQL*Plus:

GRANT SYSDBA TO system;

PASSWORD system

Changing password for system

New password: password

Retype new password: password

3. Edit

init.ora

and add the following line:

REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE

4. Restart the database instance.

As opposed to the JDBC Thin driver, the JDBC OCI driver can connect as

SYSDBA

SYSOPER

locally without specifying a password file on the server.

35-1

35.2 Using the startup Method

To start a database instance using the

startup

method, the application must first

connect to the database as a

SYSDBA

SYSOPER

in the

PRELIM_AUTH

mode, which is

the only connection mode that is permitted when the database is down. You can do

this by setting the connection property

PRELIM_AUTH

true

. In the

PRELIM_AUTH

mode,

you can only start up a database instance that is down. You cannot run any SQL

statements in this mode.

Example

The following code snippet shows how to start up a database instance that is down:

OracleDataSource ds = new OracleDataSource();

Properties prop = new Properties();

prop.setProperty("user","sys");

prop.setProperty("password","manager");

prop.setProperty("internal_logon","sysdba");

prop.setProperty("prelim_auth","true");

ds.setConnectionProperties(prop);

ds.setURL("jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)

(HOST=XYZ.com)(PORT=5221))"

+ "(CONNECT_DATA=(SERVICE_NAME=rdbms.devplmt.XYZ.com)))");

OracleConnection conn = (OracleConnection)ds.getConnection();

conn.startup(OracleConnection.DatabaseStartupMode.NO_RESTRICTION);

conn.close();

Note:

The

startup

method will start up the database using the server parameter

file. Oracle JDBC drivers do not support database startup using the client

parameter file.

35.2.1 Database Startup Options

The

startup

method takes a parameter that specifies the database startup option.

The following table lists the supported database startup options. These options are

defined in the

oracle.jdbc.OracleConnection.DatabaseStartupMode

class.

Table 35-1 Supported Database Startup Options

Option Description

FORCE

Shuts down the current instance of the database, if any, in the

ABORT

mode, before

starting a new instance.

NO_RESTRICTION

Starts up the database with no restrictions.

RESTRICT

Starts up the database and allows database access only to users with both the

CREATE

SESSION

and

RESTRICTED SESSION

privileges, typically, the DBA.

Chapter 35

Using the startup Method

35-2

The

startup

method only starts up a database instance. It neither mounts it nor opens it. For

mounting and opening the database instance, you have to reconnect as

SYSDBA

SYSOPER

without the

PRELIM_AUTH

mode.

Example

The following code snippet shows how to mount and open a database instance:

OracleDataSource ds1 = new OracleDataSource();

Properties prop1 = new Properties();

prop1.setProperty("user","sys");

prop1.setProperty("password","manager");

prop1.setProperty("internal_logon","sysdba");

ds1.setConnectionProperties(prop1);

ds1.setURL(DB_URL);

OracleConnection conn1 = (OracleConnection)ds1.getConnection();

Statement stmt = conn1.createStatement();

stmt.executeUpdate("ALTER DATABASE MOUNT");

stmt.executeUpdate("ALTER DATABASE OPEN");

35.3 Using the shutdown Method

The

shutdown

method enables you to shut down an Oracle Database instance. To use this

method, you must be connected to the database as a

SYSDBA

SYSOPER

Example

The following code snippet shows how to shut down a database instance:

OracleDataSource ds2 = new OracleDataSource();

...

OracleConnection conn2 = (OracleConnection)ds2.getConnection();

conn2.shutdown(OracleConnection.DatabaseShutdownMode.IMMEDIATE);

Statement stmt1 = conn2.createStatement();

stmt1.executeUpdate("ALTER DATABASE CLOSE NORMAL");

stmt1.executeUpdate("ALTER DATABASE DISMOUNT");

stmt1.close();

conn2.shutdown(OracleConnection.DatabaseShutdownMode.FINAL);

conn2.close();

35.3.1 Database Shutdown Options

Like the

startup

method, the

shutdown

method also takes a parameter. In this case, the

parameter specifies the database shutdown option. Table 35-2 lists the supported database

shutdown options. These options are defined in the

oracle.jdbc.OracleConnection.DatabaseShutdownMode

class.

Table 35-2 Supported Database Shutdown Options

Option Description

ABORT

Does not wait for current calls to complete or users to disconnect from the database.

CONNECT

Refuses any new connection and waits for existing connection to end.

FINAL

Shuts down the database.

IMMEDIATE

Does not wait for current calls to complete or users to disconnect from the database.

Chapter 35

Using the shutdown Method

35-3

Table 35-2 (Cont.) Supported Database Shutdown Options

Option Description

TRANSACTIONAL

Refuses new transactions and waits for active transactions to end.

TRANSACTIONAL_LOCAL

Refuses new local transactions and waits for active local transactions to end.

For shutdown options other than

ABORT

and

FINAL

, you must call the

shutdown

method

again with the

FINAL

option to actually shut down the database.

Note:

The

shutdown(DatabaseShutdownMode.FINAL)

method must be preceded by

another call to the

shutdown

method with one of the following options:

CONNECT

TRANSACTIONAL

TRANSACTIONAL_LOCAL

, or

IMMEDIATE

. Otherwise,

the call hangs.

35.3.2 Standard Database Shutdown Process

A standard way to shut down the database is as follows:

1. Initiate shutdown by prohibiting further connections or transactions in the

database. The shut down option can be either

CONNECT

TRANSACTIONAL

TRANSACTIONAL_LOCAL

, or

IMMEDIATE

2. Dismount and close the database by calling the appropriate

ALTER DATABASE

command.

3. Finish shutdown using the

FINAL

option.

In special circumstances to shut down the database as fast as possible, the

ABORT

option can be used. This is the equivalent to

SHUTDOWN ABORT

in SQL*Plus.

35.4 A Complete Example

Example 35-1 illustrates the use of the

startup

and

shutdown

methods.

Example 35-1 Database Startup and Shutdown

import java.sql.Statement;

import java.util.Properties;

import oracle.jdbc.OracleConnection;

import oracle.jdbc.pool.OracleDataSource;

/**

* To logon as sysdba, you need to create a password file for user "sys":

* orapwd file=/path/orapw password=password entries=300

* and add the following setting in init.ora:

* REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE

* then restart the database.

public class DBStartup

{

static final String DB_URL =

Chapter 35

A Complete Example

35-4

"jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost)(PORT=5221))"

+ "(CONNECT_DATA=(SERVICE_NAME=rdbms.devplmt.XYZ.com)))";

public static void main(String[] argv) throws Exception

{

// Starting up the database:

OracleDataSource ds = new OracleDataSource();

Properties prop = new Properties();

prop.setProperty("user","sys");

prop.setProperty("password","manager");

prop.setProperty("internal_logon","sysdba");

prop.setProperty("prelim_auth","true");

ds.setConnectionProperties(prop);

ds.setURL(DB_URL);

OracleConnection conn = (OracleConnection)ds.getConnection();

conn.startup(OracleConnection.DatabaseStartupMode.NO_RESTRICTION);

conn.close();

// Mounting and opening the database

OracleDataSource ds1 = new OracleDataSource();

Properties prop1 = new Properties();

prop1.setProperty("user","sys");

prop1.setProperty("password","manager");

prop1.setProperty("internal_logon","sysdba");

ds1.setConnectionProperties(prop1);

ds1.setURL(DB_URL);

OracleConnection conn1 = (OracleConnection)ds1.getConnection();

Statement stmt = conn1.createStatement();

stmt.executeUpdate("ALTER DATABASE MOUNT");

stmt.executeUpdate("ALTER DATABASE OPEN");

stmt.close();

conn1.close();

// Shutting down the database

OracleDataSource ds2 = new OracleDataSource();

Properties prop = new Properties();

prop.setProperty("user","sys");

prop.setProperty("password","manager");

prop.setProperty("internal_logon","sysdba");

ds2.setConnectionProperties(prop);

ds2.setURL(DB_URL);

OracleConnection conn2 = (OracleConnection)ds2.getConnection();

conn2.shutdown(OracleConnection.DatabaseShutdownMode.IMMEDIATE);

Statement stmt1 = conn2.createStatement();

stmt1.executeUpdate("ALTER DATABASE CLOSE NORMAL");

stmt1.executeUpdate("ALTER DATABASE DISMOUNT");

stmt1.close();

conn2.shutdown(OracleConnection.DatabaseShutdownMode.FINAL);

conn2.close();

}

Chapter 35

A Complete Example

35-5

Diagnosability in JDBC

The diagnosabilty features of Oracle Database 12c Release 1 (12.1) enable you to diagnose

problems in the applications that use Oracle JDBC drivers and the problems in the drivers

themselves. They also reduce the effort required to develop and maintain Java applications

that access an Oracle Database instance using Oracle JDBC drivers.

Oracle JDBC drivers provide the following diagnosabilty features that enable users to identify

and fix problems in their JDBC applications:

• Logging Feature of Oracle JDBC Drivers

• Diagnosability Management

Note:

The diagnosability features of the JDBC drivers are based on the standard

java.util.logging

framework and the

javax.management

MBean framework.

Information about these standard frameworks is not covered in this document.

36.1 About Logging Feature of Oracle JDBC Drivers

This section describes the following concepts:

• Overview of Logging Feature of Oracle JDBC Drivers

• Enabling and Using JDBC Logging

• Enabling or Disabling Feature-Specific Logging at Runtime

• Using the Logging Configuration File for Feature-Specific Logging

• Performance, Scalability, and Security Issues

36.1.1 Overview of Logging Feature of Oracle JDBC Drivers

This feature logs information about events that occur when JDBC driver code runs. Events

can include user-visible events, such as SQL exceptions, running of SQL statements, and

detailed JDBC internal events, such as entry to and exit from internal JDBC methods. Users

can enable this feature to log specific events or all the events.

Prior to Oracle Database 11g, JDBC drivers supported J2SE 2.0 and 3.0. These versions of

J2SE did not include

java.util.logging

. Therefore, the logging feature provided by JDBC

driver releases prior to Oracle Database 11g, differs from the

java.util.logging

framework.

Starting from Oracle Database 11g, the JDBC drivers no longer support J2SE 2.0 and 3.0.

Therefore, the logging feature of JDBC drivers makes full use of the standard

java.util.logging

package. The enhanced logging system makes effective use of log levels

36-1

to enable users to restrict log output to things of interest. It logs specific classes of

information more consistently, making it easier for the user to understand the log file.

This feature does not introduce new APIs or configuration files. Only new parameters

are added to the existing standard

java.util.logging

configuration file. These

parameters are identical in use to the existing parameters and are intrinsic to using

java.util.logging

Note:

Oracle does not guarantee the exact content of the generated logs. To a

large extent the log content is dependent on the details of the

implementation. The details of the implementation change with every

release, and therefore, the exact content of the logs are likely to change from

release to release.

36.1.2 Enabling and Using JDBC Logging

Before you can start debugging your Java application, you must enable and configure

JDBC logging. This section covers the steps you must perform to enable and use

JDBC logging. It describes the following:

• About Configuring the CLASSPATH

• Enabling Logging

• Configuring Logging

• Using Loggers

• Logging Example

36.1.2.1 About Configuring the CLASSPATH

Oracle ships several JAR files for each version of the JDBC drivers. The optimized

JAR files do not contain any logging code and, therefore, do not generate any log

output when used. To get log output, you must use the debug JAR files, which are

indicated with a "_g" in the file name, like

ojdbc6_g.jar

ojdbc7_g.jar

. The debug

JAR file must be included in the

CLASSPATH

Note:

Ensure that the debug JAR file, say

ojdbc6_g.jar

ojdbc7_g.jar

, is the

only Oracle JDBC JAR file in the

CLASSPATH

36.1.2.2 Enabling Logging

You can enable logging in the following ways:

• Setting a Java system property

You can enable logging by setting the

oracle.jdbc.Trace

system property.

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About Logging Feature of Oracle JDBC Drivers

36-2

java -Doracle.jdbc.Trace=true ...

Setting the system property enables global logging, which means that logging is enabled

for the entire application. You can use global logging if you want to debug the entire

application, or if you cannot or do not want to change the source code of the application.

• Programmatically

You can programmatically enable or disable logging in the following way:

First, get the

ObjectName

of the Diagnosability MBean. The

ObjectName

com.oracle.jdbc:type=diagnosability,name=<loader>

Here,

loader

is a unique name based on the class loader instance that loaded the Oracle

JDBC drivers.

Note:

The drivers can be loaded multiple times in a single VM. So, there can be

multiple MBeans, each with a unique name.

Now, write the following lines of code:

ClassLoader l = oracle.jdbc.OracleDriver.getClassLoader();

String loader = l.getName() + "@" + l.hashCode();

// compute the ObjectName

javax.management.ObjectName name = new

javax.management.ObjectName("com.oracle.jdbc:type=diagnosability,

name="+loader);

// get the MBean server

javax.management.MBeanServer mbs =

java.lang.management.ManagementFactory.getPlatformMBeanServer();

// find out if logging is enabled or not

System.out.println("LoggingEnabled = " + mbs.getAttribute(name, "LoggingEnabled"));

// enable logging

mbs.setAttribute(name, new javax.management.Attribute("LoggingEnabled", true));

// disable logging

mbs.setAttribute(name, new javax.management.Attribute("LoggingEnabled", false));

Note:

– If the same class loader loads the JDBC drivers multiple times, then each

subsequent MBean increments the value of the

l.hashCode()

method, so

as to create a unique name. It may be problematic to identify which MBean

is associated with which JDBC driver instance.

– If there is only one instance of the JDBC drivers loaded, then set the name

to "*".

Chapter 36

About Logging Feature of Oracle JDBC Drivers

36-3

Programmatic enabling and disabling of logging helps you to control what parts of your

application need to generate log output.

Note:

Enabling logging using either of the methods would only generate a minimal

log of serious errors. Usually this is not of much use. To generate a more

useful and detailed log, you must configure

java.util.logging

36.1.2.3 Configuring Logging

To generate a useful and detailed log, you must configure

java.util.logging

. This

can be done either through a configuration file or programmatically.

A sample configuration file,

OracleLog.properties

, is provided as part of the JDBC

installation in the

demo

directory. It contains basic information about how to configure

java.util.logging

and provides some initial settings that you can start with. You may

use this sample file as is, edit the file and use it, rename the file and edit it, or create

an entirely new file of any name.

To use a configuration file, you must identify it to the Java run-time. This can be done

by setting a system property. For example:

java -Djava.util.logging.config.file=/jdbc/demo/OracleLog.properties.

It is read by the

java.util.logging

system. This file can reside anywhere.

You can use both

java.util.logging.config.file

and

oracle.jdbc.Trace

at the

same time.

java -Djava.util.logging.config.file=/jdbc/demo/OracleLog.properties -

Doracle.jdbc.Trace=true

You can use the default

OracleLog.properties

file. It may or may not get you the

desired output. You can also create and use your own configuration file by following

these steps:

1. Create a file named

myConfig.properties

. You can use any name you choose.

2. Insert the following lines of text in the file:

.level=SEVERE

oracle.jdbc.level=INFO

oracle.jdbc.handlers=java.util.logging.ConsoleHandler

java.util.logging.ConsoleHandler.level=INFO

java.util.logging.ConsoleHandler.formatter=java.util.logging.SimpleFormatter

3. Save the file.

4. Set the system property to use this configuration file.

java -Djava.util.logging.config.file=<filepath>/myConfig.properties ...

filepath

is the path of the folder where you have saved the

myConfig.properties

file.

Chapter 36

About Logging Feature of Oracle JDBC Drivers

36-4

Note:

If you use the settings specified in Step 2, then a huge amount of log output will be

generated. Also, the log output will be displayed on the console.

36.1.2.4 Redirecting the Log Output to a File

You can also configure

java.util.logging

to redirect the log output into a file. To do so,

modify the configuration file as follows:

.level=SEVERE

oracle.jdbc.level=INFO

oracle.jdbc.handlers=java.util.logging.FileHandler

java.util.logging.FileHandler.level=INFO

java.util.logging.FileHandler.pattern=jdbc.log

java.util.logging.FileHandler.count=1

java.util.logging.FileHandler.formatter=java.util.logging.SimpleFormatter

This will generate exactly the same log output and save it in a file named

jdbc.log

in the

current directory.

You can control the amount of detail by changing the level settings. The defined levels from

the least detailed to the most detailed are the following:

•

OFF

Turns off logging.

•

SEVERE

Logs SQLExceptions and internal errors.

•

WARNING

Logs SQLWarnings and bad but not fatal internal conditions.

•

INFO

Logs infrequent but significant events and errors. It produces a relatively low volume of

log messages.

•

CONFIG

Logs SQL strings that are executed.

•

FINE

Logs the entry and exit to every public method providing a detailed trace of JDBC

operations. It produces a fairly high volume of log messages.

•

FINER

Logs calls to internal methods.

•

FINEST

Logs calls to high volume internal methods.

•

ALL

Logs all the details. This is the most detailed level of logging.

Chapter 36

About Logging Feature of Oracle JDBC Drivers

36-5

Note:

Levels more detailed than

FINE

generate huge log volumes.

In the example provided earlier, to reduce the amount of detail, change the

java.util.logging.FileHandler.level

setting from

ALL

INFO

java.util.logging.FileHandler.level=INFO

Note:

INFO

logs the SQL strings that are executed.

Although you can, it is not necessary to change the level of the

oracle.jdbc

logger.

Setting the

FileHandler

level will control what log messages are dumped into the log

file.

36.1.2.5 Using Loggers

Setting the level reduces all the logging output from JDBC. However, sometimes you

need a lot of output from one part of the code and very little from other parts. To do

that you must understand more about loggers.

Loggers exist in a tree structure defined by their names. The root logger is named "",

the empty string. If you look at the first line of the configuration file you

see

.level=SEVERE

. This is setting the level of the root logger. The next line is

oracle.jdbc.level=INFO

. This sets the level of the logger named

oracle.jdbc

. The

oracle.jdbc

logger is a member of the logger tree. Its parent is named

oracle

. The

parent of the

oracle

logger is the root logger (the empty string).

Logging messages are sent to a particular logger, for example,

oracle.jdbc

. If the

message passes the level check at that level, then the message is passed to the

handler at that level, if any, and to the parent logger. So a log message sent to

oracle.log

is compared against that logger's level,

INFO

if you are following along. If

the level is the same or less (less detailed) then it is sent to the FileHandler and to the

parent logger, 'oracle'. Again it is checked against the level. If as in this case, the level

is not set then it uses the parent level,

SEVERE

. If the message level is the same or less

it is passed to the handler, which there is not one, and sent to the parent. In this case

the parent in the root logger.All this tree structure did not help you reduce the amount

of output. What will help is that the JDBC drivers use several subloggers. If you restrict

the log messages to one of the subloggers you will get substantially less output. The

loggers used by Oracle JDBC drivers include the following:

•

oracle.jdbc

•

oracle.jdbc.pool

•

oracle.jdbc.rowset

•

oracle.jdbc.xa

•

oracle.sql

Chapter 36

About Logging Feature of Oracle JDBC Drivers

36-6

Note:

The loggers used by the drivers may vary from release to release.

36.1.2.6 Logging Example

Suppose you want to trace what is happening in the

oracle.sql

component and also want to

capture some basic information about the rest of the driver. This is a more complex use of

logging. The following are the entries in the

config

file:

# set levels

.level=SEVERE

oracle.level=INFO

oracle.jdbc.driver.level=INFO

oracle.jdbc.pool.level=OFF

oracle.jdbc.util.level=OFF

oracle.sql.level=INFO

# configure handlers

oracle.handlers=java.util.logging.ConsoleHandler

java.util.logging.ConsoleHandler.level=INFO

java.util.logging.ConsoleHandler.formatter=java.util.logging.SimpleFormatter

Let us consider what each line in the configuration file is doing.

.level=SEVERE

Sets the logging level of the root logger to

SEVERE

. We do not want to see any logging from

other, non-Oracle components unless something fails badly. Therefore, we set the default

level for all loggers to

SEVERE

. Each logger inherits its level from its parent unless set

explicitly. By setting the level of the root logger to

SEVERE

we ensure that all other loggers

inherit that level except for the ones we set otherwise.

oracle.level=INFO

We want log output from both the

oracle.sql

and

oracle.jdbc.driver

loggers. Their

common ancestor is

oracle

. Therefore, we set the level of the

oracle

logger to

INFO

. We will

control the detail more explicitly at lower levels.

oracle.jdbc.driver.level=INFO

We only want to see the SQL execution from

oracle.jdbc.driver

. Therefore, we set the

level to

INFO

. This is a fairly low volume level, but will help us to keep track of what our test is

doing.

oracle.jdbc.pool.level=OFF

We are using a

DataSource

in our test and do not want to see all of that logging. Therefore,

we turn it

OFF

oracle.jdbc.util.level=OFF

Chapter 36

About Logging Feature of Oracle JDBC Drivers

36-7

We do not want to see the logging from the

oracle.jdbc.util

package. If we were

using XA or row sets we would turn them off as well.

oracle.sql.level=INFO

We want to see what is happening in

oracle.sql

. Therefore, we set the level to

INFO

This provides a lot of information about the public method calls without overwhelming

detail.

oracle.handlers=java.util.logging.ConsoleHandler

We are going to dump everything to

stderr

. When we run the test we will redirect

stderr

to a file.

java.util.logging.ConsoleHandler.level=INFO

We want to dump everything to the console which is

System.err

. In this case, we are

doing the filtering with the loggers rather than the handler.

java.util.logging.ConsoleHandler.formatter=java.util.logging.SimpleFormatter

We will use a simple, more or less human readable format.

When you run your test with this configuration file, you will get moderately detailed

information from the

oracle.sql

package, a little bit of information from the core driver

code, and nothing from any other code.

You can also use

XMLFormatter

for sending logs to Oracle Support.

You can implement and use a custom

java.util.logging.Filter

to obtain finer

control of the data captured in the logs. This is a standard

java.util.logging

feature

and is documented in the JSE JavaDoc. A custom Filter enables you to:

• Capture only one thread in multithreaded applications

• Capture intermittent errors in long running applications

36.1.3 Enabling or Disabling Feature-Specific Logging at Run Time

Starting from Oracle Database 12c Release 2 (12.2.0.1), JDBC provides support for

enabling and disabling feature-specific logging for selected features during runtime.

For example, you can enable logging only for Load Balancing feature, while disabling

logging for other features of JDBC. Again, during the same run, you can enable

logging for Fast Connection Failover feature and disable logging for Load Balancing

feature.

By default, logging for all features is enabled.

The logging switching knob of JDBC is a part of the

OracleDiagnosabilityMBean

. For

using this bean, start JConsole and connect to the application.

Displaying Supported Features

For a list of supported features, use the following method:

getTraceController().getSupportedFeatures()

Displaying Enabled Features

Chapter 36

About Logging Feature of Oracle JDBC Drivers

36-8

For a list of currently enabled features, use the following method:

getTraceController().getEnabledFeatures()

Enabling Logging for a Feature

For enabling logging for a specific feature or for all features, use the

trace

method in the

following ways:

trace(boolean enable, String feature_name)

trace(boolean enable, ALL)

Disabling Logging for a Feature

For disabling logging for a specific feature or for all features, use the

trace

method in the

following ways:

trace(boolean disable, String feature_name)

trace(boolean disable, ALL)

Suspending and Resuming Logging

Use the following methods for suspending and resuming logging respectively:

suspend()

resume()

36.1.4 Using the Logging Configuration File for Feature-Specific Logging

This section describes how to use the logging configuration file for enabling or disabling

feature-specific logging.

Starting from Oracle Database 12c Release 2 (12.2.0.1), you can enable or disable logging

for specific features by adding a property in the logging configuration file. By default, logging

is enabled for all features. Otherwise, you can enable logging for all features using the

following syntax:

clio.feature.all = on

For feature-specific enabling of logging, you can use the following properties:

clio.feature.character_set_conversion = on

clio.feature.column_get = on

clio.feature.connect = on

clio.feature.date_time = on

clio.feature.metadata = on

clio.feature.object_types = on

clio.feature.parameter_set = on

clio.feature.protocol_violation = on

clio.feature.result_fetch = on

clio.feature.result_set_cache = on

clio.feature.scrollable_result_set = on

clio.feature.security = on

clio.feature.sensitive_result_set = on

Chapter 36

About Logging Feature of Oracle JDBC Drivers

36-9

clio.feature.sql_execution = on

clio.feature.sql_rewrite = on

clio.feature.sql_translation = on

clio.feature.statement_cache = on

clio.feature.updateable_result_set = on

clio.feature.platform = on

clio.feature.exceptional_execution = on

clio.feature.thin_internal = on

clio.feature.server_internal = on

clio.feature.sql_converter = on

clio.feature.rowset = on

clio.feature.oci_internal = on

clio.feature.conn_pool = on

clio.feature.xa = on

clio.feature.change_notification = on

clio.feature.net = on

clio.feature.advanced_queuing = on

clio.feature.conn_management = on

clio.feature.application_continuity = on

clio.feature.forwarding = on

clio.feature.abstract_datum = on

clio.feature.primitive_datum = on

clio.feature.lob_datum = on

clio.feature.lob_helper = on

clio.feature.character_datum = on

clio.feature.character_processing = on

clio.feature.character_forwarding = on

clio.feature.object_datum = on

clio.feature.object_processing = on

clio.feature.collection_datum = on

clio.feature.object_metadata = on

clio.feature.collection_metadata = on

clio.feature.object_pickler = on

clio.feature.collection_pickler = on

36.1.5 Performance, Scalability, and Security Issues

Although the logging feature enables you to trace or debug your application and

generate detail log output, it has certain performance, scalability, and security issues.

Caution:

Trace files are likely to contain sensitive information including user names,

passwords, and user data. Oracle recommends that users do not use JDBC

debug JAR files with production data or credentials, so as to protect that

sensitive information. In addition, Oracle recommends that users must follow

good security practices for creating trace files.

Security Concerns

Enabling full logging creates the risk that sensitive information will be exposed in the

trace files. This is intrinsic to the logging feature. However, only certain JDBC JAR files

Chapter 36

About Logging Feature of Oracle JDBC Drivers

36-10

include the JDBC logging feature. The following JAR files include full logging and should not

be used in a production environment:

•

ojdbc8_g.jar

•

ojdbc8dms_g.jar

The

ojdbc8dms.jar

JAR file includes a limited logging capability.

Note:

Database user names and passwords do not appear in log files created by the

ojdbc8_g.jar

and the

ojdbc8dms_g.jar

JAR files. However, sensitive user data

that is part of a SQL statement, a defined value, or a bind value can appear in a log

created using one of these JAR files.

About Secure Handling of Trace Files

For secure handling of trace files, you must:

• Trace only as much of the execution as needed to minimize the amount of sensitive

information in the trace file.

• Create the trace file in a directory owned by you. Do not create the file in common public

directories, such as the /tmp directory.

• Set the

UMASK

for the directory where the trace file is created. This will restrict user access

to the trace file.

• Not enable the

append

option in

java.util.logging.FileHandler

. This will provide

better control over the owner and permissions on the trace file.

• Not grant

LoggingPermission

to the JDBC code base, when using the

ojdbc8.jar

file.

The

ojdbc8dms.jar

file provides limited log output and requires

LoggingPermission

. The

debug JAR files,

ojdbc8_g.jar

and

ojdbc8dms_g.jar

have extensive trace and require

LoggingPermission

Performance and Scalability Issues

Logging has substantial impact on performance. You must make sure that logging is not

enabled in production systems. Also, you must not use the debug JAR files in a production

environment. When logging is disabled, it has no impact on performance.

Logging involves protected access to a number of shared resources resulting in severely

reduced scalability. This is intrinsic to the

java.util.logging

framework.

36.2 Diagnosability Management

The JDBC diagnosability management feature introduces an MBean,

oracle.jdbc.driver.OracleDiagnosabilityMBean

. This MBean provides means to enable

and disable JDBC logging.

Chapter 36

Diagnosability Management

36-11

See Also:

For information about the

OracleDiagnosabilityMBean

API, refer to the

JDBC Javadoc.

In future releases, the MBean will be enhanced to provide additional statistics about

JDBC internals.

Security Concerns

This feature can enable JDBC logging. Enabling JDBC logging does not require any

special permission. However, once logging is enabled, generating any log output

requires the standard Java permission

LoggingPermission

. Without this permission,

any JDBC operation that would generate log output will throw a security exception.

This is a standard Java mechanism.

Chapter 36

Diagnosability Management

36-12

JDBC DMS Metrics

DMS metrics are used to measure the performance of application components.

This chapter discusses the following topics:

• Overview of JDBC DMS Metrics

• About Determining the Type of Metric to Be Generated

• About Generating the SQLText Metric

• About Accessing DMS Metrics Using JMX

Note:

There is another kind of metrics called end-to-end metrics. End-to-end metrics are

used for tagging application activity from the entry into the application code through

JDBC to the database and back.

JDBC supports the following end-to-end metrics:

•

Action

•

ClientId

•

ExecutionContextId

•

Module

•

State

For earlier releases, to work with the preceding metrics, you could use the

setEndToEndMetrics

and

getEndToEndMetrics

methods of the

oracle.jdbc.OracleConnection

interface. However, starting from Oracle Database

12c Release 1 (12.1), these methods have been deprecated. Oracle recommends

to use the

setClientInfo

and

getClientInfo

methods instead of the

setEndToEndMetrics

and

getEndToEndMetrics

methods.

In Oracle Database 10g, Oracle Java Database Connectivity (JDBC) supports end-

to-end metrics. In Oracle Database 12c Release 1 (12.1), an application can set the

end-to-end metrics directly only when it does not use a DMS-enabled JAR files. But,

if the application uses a DMS-enabled JAR file, the end-to-end metrics can be set

only through DMS.

WARNING:

Oracle strongly recommends using DMS metrics, if the application uses a DMS-

enabled JAR file.

37-1

See Also:

Oracle Database JDBC Java API Reference for more information about end-

to-end metrics

37.1 Overview of JDBC DMS Metrics

DMS metrics enable application and system developers to measure and export

customized performance metrics for specific software components.

All DMS metrics are available in the following DMS-enabled JAR files:

•

ojdbc8dms.jar

•

ojdbc8dms_g.jar

•

ojdbc11dms.jar

•

ojdbc11dms_g.jar

Any other JDBC JAR files do not generate any DMS metrics. The metrics generated in

Oracle Database 21c are different from the metrics generated for earlier versions of

Oracle JDBC as it makes no attempt to retain compatibility with earlier versions. There

are also no compatibility modes. A system that is dependent on the exact details of the

DMS metrics generated by earlier versions of JDBC may have unexpected behavior

when processing the metrics generated by Oracle JDBC 21c. This is by design and

cannot be changed.

Statement metrics can be reported consolidated for all statements in a connection or

individually for each statement. All DMS metrics, except those related to individual

statements, are enabled at all times.

Note:

You can enable or disable the

SQLText

statement metric. It is disabled by

default. If enabled, it is enabled for all statements.

37.2 About Determining the Type of Metric to Be Generated

To determine whether to use consolidated or individual metrics, JDBC checks the

DMSConsole sensor weight. If the sensor weight is less than or equal to

DMSConsole.NORMAL

, then JDBC generates consolidated statement metrics. If the

sensor weight is greater than

DMSConsole.NORMAL

, then JDBC generates individual

statement metrics.

JDBC checks the DMSConsole sensor weight when creating a Prepared or Callable

statement and depending on the sensor weight at the time the statement is created,

the metrics are generated. Changing the value of the sensor weight, after the

statement has been created, does not cause a statement to switch between

consolidated and individual metrics.

Chapter 37

Overview of JDBC DMS Metrics

37-2

Note:

In the presence of Statement caching, it may appear that changing sensor weight

has no impact as statements are retrieved from the cache rather than created anew.

There is only one list of statement metrics that is generated for both consolidated and

individual statement metrics. The only difference between these two lists is the aggregation of

the statements. When individual statement metrics are generated, one set of metrics is

generated for each distinct statement object created by the JDBC driver. On the other hand,

when consolidated statement metrics are generated, all statements created by a given

connection use the same set of statement metrics.

For example, consider an '

execute

' phase event. If individual statement metrics are used,

then each statement created will have a distinct '

execute

' phase event. So, from two such

statements, it will be possible to distinguish the execution statistics for the two separate

statements. If one has an execution time of 1 second and the other an execution time of 3

seconds, then there will be two distinct 'execute' phase events, one with a total time and

average of 1 second and the other with a total time and average of 3 seconds. But, if

consolidated statement metrics are used, all statements will use the single '

execute

' phase

event common to the connection. So, from two such statements created by the same

connection, it will not be possible to distinguish the execution statistics for the two

statements. If one has an execution time of 1 second and the other an execution time of 3

seconds, then the common '

execute

' phase event will report a total execution time of 4

seconds and an average of 2 seconds.

37.3 About Generating the SQLText Metric

Depending on the version of DMS, there are two mechanisms for determining the generating

of the

SQLText

statement metrics:

• If the 12c version of the DMS JAR file is present in the

classpath

environment variable,

then JDBC checks the DMS update SQL text flag. If this flag is

true

, then the

SQLText

metric is updated.

• If the 12c version of the DMS JAR file is not present in the

classpath

environment

variable, then JDBC uses the value of the

DMSStatementMetrics

connection property. If

this statement property is

true

, then

SQLText

metric is updated. The default value of this

connection property is

false

Whether or not the

SQLText

metric will be generated is independent of the use of the type of

statement metrics used, that is, individual statement metrics or consolidated statement

metrics.

37.4 About Accessing DMS Metrics Using JMX

JMX (Java Management Extensions) is a Java technology that supplies tools for managing

and monitoring applications, system objects, devices, service-oriented networks, and the

JVM (Java Virtual Machine). You can easily access DMS metrics at run time using a

management application that supports JMX. For more information about using JMX to access

DMS data, go to the following URL

http://www.oracle.com/technetwork/middleware/

toplink/overview/index.html

Chapter 37

About Generating the SQLText Metric

37-3

See Also:

Oracle Database Java Developer's Guide for more information about JMX

Chapter 37

About Accessing DMS Metrics Using JMX

37-4

Part IX

Appendixes

This part consists of appendixes that discuss Java Database Connectivity (JDBC) reference

information, tips for coding JDBC applications, JDBC error messages, and troubleshooting

JDBC applications.

Part IX contains the following appendixes:

• JDBC Reference Information

• Oracle RAC Fast Application Notification

• JDBC Coding Tips

• JDBC Error Messages

• Troubleshooting

JDBC Reference Information

This appendix contains detailed Java Database Connectivity (JDBC) reference information,

including the following topics:

• Supported SQL-JDBC Data Type Mappings

• Supported SQL and PL/SQL Data Types

• About Using PL/SQL Types

• Using Embedded JDBC Escape Syntax

• Oracle JDBC Notes and Limitations

A.1 Supported SQL-JDBC Data Type Mappings

The following table lists all the possible Java types to which a given SQL data type can be

validly mapped. Oracle JDBC drivers will support these nondefault mappings. For example,

to materialize SQL

CHAR

data in an

oracle.sql.CHAR

object, use the

getCHAR

method. To

materialize it as a

java.math.BigDecimal

object, use the

getBigDecimal

method.

Note:

The classes, where

oracle.jdbc.OracleData

appears in italic, can be generated

by Oracle JVM Web Services Call-Out Utility.

Table A-1 Valid SQL Data Type-Java Class Mappings

SQL data type Java types

CHAR

VARCHAR2

LONG java.lang.String

oracle.sql.CHAR

A-1

Table A-1 (Cont.) Valid SQL Data Type-Java Class Mappings

SQL data type Java types

NUMBER boolean

char

byte

short

int

long

float

double

java.lang.Byte

java.lang.Short

java.lang.Integer

java.lang.Long

java.lang.Float

java.lang.Double

java.math.BigDecimal

oracle.sql.NUMBER

BINARY_INTEGER boolean

char

byte

short

int

long

BINARY_FLOAT oracle.sql.BINARY_FLOAT

BINARY_DOUBLE oracle.sql.BINARY_DOUBLE

DATE oracle.sql.DATE

RAW oracle.sql.RAW

BLOB oracle.jdbc.OracleBlob

CLOB oracle.jdbc.OracleClob

BFILE oracle.sql.BFILE

ROWID oracle.sql.ROWID

TIMESTAMP oracle.sql.TIMESTAMP

TIMESTAMP WITH TIME ZONE oracle.sql.TIMESTAMPTZ

TIMESTAMP WITH LOCAL TIME

ZONE

oracle.sql.TIMESTAMPLTZ

ref cursor j

ava.sql.ResultSet

sqlj.runtime.ResultSetIterator

user defined named types, ADTs

oracle.jdbc.OracleStruct

opaque named types

oracle.jdbc.OracleOpaque

Appendix A

Supported SQL-JDBC Data Type Mappings

A-2

Table A-1 (Cont.) Valid SQL Data Type-Java Class Mappings

SQL data type Java types

nested tables and VARRAY named

types

oracle.jdbc.OracleArray

references to named types

oracle.jdbc.OracleRef

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.BLOB

class is deprecated and replaced

with the

oracle.jdbc.OracleBlob

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.CLOB

class is deprecated and replaced

with the

oracle.jdbc.OracleClob

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.STRUCT

class is deprecated and

replaced with the

oracle.jdbc.OracleStruct

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.OPAQUE

class is deprecated and

replaced with the

oracle.jdbc.OracleOpaque

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.ARRAY

class is deprecated and replaced

with the

oracle.jdbc.OracleArray

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.REF

class is deprecated and replaced

with the

oracle.jdbc.OracleRef

interface.

Note:

• The type

UROWID

is not supported.

• The

oracle.sql.Datum

class is abstract. The value passed to a parameter of

type

oracle.sql.Datum

must be of the Java type corresponding to the

underlying SQL type. Likewise, the value returned by a method with return type

oracle.sql.Datum

must be of the Java type corresponding to the underlying

SQL type.

A.2 Supported SQL and PL/SQL Data Types

The tables in this section list SQL and PL/SQL data types, and Oracle JDBC driver support

for them. The following table describes Oracle JDBC driver support for SQL data types.

Table A-2 Support for SQL Data Types

SQL Data Type Supported by JDBC Drivers?

BFILE yes

BLOB yes

CHAR yes

CLOB yes

DATE yes

NCHAR no

NCHAR VARYING no

NUMBER yes

Appendix A

Supported SQL and PL/SQL Data Types

A-3

Table A-2 (Cont.) Support for SQL Data Types

SQL Data Type Supported by JDBC Drivers?

NVARCHAR2 yes

RAW yes

REF yes

ROWID yes

UROWID no

VARCHAR2 yes

The NCHAR type is supported indirectly. There is no corresponding java.sql.Types type, but if your

application calls the formOfUse(NCHAR) method, then this type can be accessed.

In JSE 6, the NVARCHAR2 type is supported directly. In J2SE 5.0, the NVARCHAR2 type is supported

indirectly. There is no corresponding java.sql.Types type, but if your application calls the

formOfUse(NCHAR) method, then this type can be accessed.

The following table describes Oracle JDBC support for the ANSI-supported SQL data

types.

Table A-3 Support for ANSI-92 SQL Data Types

ANSI-Supported SQL Data Type Supported by JDBC Drivers?

CHARACTER yes

DEC yes

DECIMAL yes

DOUBLE PRECISION yes

FLOAT yes

INT yes

INTEGER yes

NATIONAL CHARACTER no

NATIONAL CHARACTER VARYING no

NATIONAL CHAR yes

NATIONAL CHAR VARYING no

NCHAR yes

NCHAR VARYING no

NUMERIC yes

REAL yes

SMALLINT yes

VARCHAR yes

The following table describes Oracle JDBC driver support for SQL User-Defined types.

Appendix A

Supported SQL and PL/SQL Data Types

A-4

Table A-4 Support for SQL User-Defined Types

SQL User-Defined type Supported by JDBC Drivers?

OPAQUE yes

Reference types yes

Object types (

JAVA_OBJECT

) yes

Nested table types and VARRAY types yes

The following table describes Oracle JDBC driver support for PL/SQL data types. The

PL/SQL data types include the following categories:

• Scalar types

• Scalar character types, which includes

DATE

data type

• Composite types

• Reference types

• Large object (LOB) types

Table A-5 Support for PL/SQL Data Types

PL/SQL Data Type Supported by JDBC Drivers?

Scalar Types:

BINARY INTEGER yes

DEC yes

DECIMAL yes

DOUBLE PRECISION yes

FLOAT yes

INT yes

INTEGER yes

NATURAL yes

NATURALn no

NUMBER yes

NUMERIC yes

PLS_INTEGER yes

POSITIVE yes

POSITIVEn no

REAL yes

SIGNTYPE yes

SMALLINT yes

BOOLEAN yes

Scalar Character Types:

CHAR yes

CHARACTER yes

Appendix A

Supported SQL and PL/SQL Data Types

A-5

Table A-5 (Cont.) Support for PL/SQL Data Types

PL/SQL Data Type Supported by JDBC Drivers?

LONG yes

LONG RAW yes

NCHAR no (see Note)

NVARCHAR2 no (see Note)

RAW yes

ROWID yes

STRING yes

UROWID no

VARCHAR yes

VARCHAR2 yes

DATE yes

Composite Types:

RECORD no

TABLE no

VARRAY yes

Reference Types:

REF CURSOR types yes

object reference types yes

LOB Types:

BFILE yes

BLOB yes

CLOB yes

NCLOB yes

Note:

• The types

NATURAL

NATURALn

POSITIVE

POSITIVEn

, and

SIGNTYPE

are

subtypes of

BINARY INTEGER

• The types

DEC

DECIMAL

DOUBLE PRECISION

FLOAT

INT

INTEGER

NUMERIC

REAL

, and

SMALLINT

are subtypes of

NUMBER

• The types

NCHAR

and

NVARCHAR2

are supported indirectly. There is no

corresponding

java.sql.Types

type, but if your application calls

formOfUse(NCHAR)

, then these types can be accessed.

Related Topics

• NCHAR, NVARCHAR2, NCLOB and the defaultNChar Property

Appendix A

Supported SQL and PL/SQL Data Types

A-6

A.3 About Using PL/SQL Types

Starting from Oracle Database 12c Release 1 (12.1), you can map schema-level PL/SQL

types as generic

java.sql.Struct

type and PL/SQL collections as

java.sql.Array

types.

So, instead of creating schema-level types that are mapped to PL/SQL package types for

binding, you can describe and bind PL/SQL types using only the JDBC APIs.

For example, you can call the

Connection.createStruct(type_name)

method to first create a

descriptor that can be used to describe a PL/SQL type and then to create a new

STRUCT

representation of this type on the client. In Oracle Database 12c Release 1 (12.1), you can

reuse this API by specifying

type_name

“schema.package.typename"

“package.typename"

All PL/SQL package types are mapped to a system-wide unique name that can be used by

JDBC to retrieve the server-side type metadata. The name is in the following form:

[SCHEMA.]<PACKAGE>.<TYPE>

Note:

If the schema is the same as the package name, and if there is a type with the

same name as the PL/SQL type, then it will not be able to identify an object with the

two part name format, that is, <package>.<type>. In such cases, you must use

three part names <schema>.<package>.<type>.

The following code snippet explains how to bind types declared in PL/SQL packages:

---------------------------

# Perform the following SQL operations prior to running this sample

---------------------------

conn HR/hr;

create or replace package TEST_PKG is

type V_TYP is varray(10) of varchar2(200);

type R_TYP is record(c1 pls_integer, c2 varchar2(100));

procedure VARR_PROC(p1 in V_TYP, p2 OUT V_TYP);

procedure REC_PROC(p1 in R_TYP, p2 OUT R_TYP);

end;

create or replace package body TEST_PKG is

procedure VARR_PROC(p1 in V_TYP, p2 OUT V_TYP) is

begin

p2 := p1;

end;

procedure REC_PROC(p1 in R_TYP, p2 OUT R_TYP) is

begin

p2 := p1;

end;

import java.sql.Array;

import java.sql.CallableStatement;

import java.sql.Connection;

Appendix A

About Using PL/SQL Types

A-7

import java.sql.SQLException;

import java.sql.Struct;

import java.sql.Types;

import oracle.jdbc.OracleConnection;

public class PLSQLTypesSample

{

public static void main(String[] args) throws SQLException

{

System.out.println("begin...");

Connection conn = null;

oracle.jdbc.pool.OracleDataSource ods = new

oracle.jdbc.pool.OracleDataSource();

ods.setURL("jdbc:oracle:oci:localhost:5521:orcl");

ods.setUser("HR");

ods.setPassword("hr");

//get connection

conn = ods.getConnection();

//call procedure TEST_PKG.VARR_PROC

CallableStatement cstmt = null;

try {

cstmt = conn.prepareCall("{ call TEST_PKG.VARR_PROC(?,?) }");

//PLSQL VARRAY type binding

Array arr = ((OracleConnection)conn).createArray("TEST_PKG.V_TYP", new

String[]{"A", "B"});

cstmt.setArray(1, arr);

cstmt.registerOutParameter(2, Types.ARRAY, "TEST_PKG.V_TYP");

cstmt.execute();

//get PLSQL VARRAY type out parameter value

Array outArr = cstmt.getArray(2);

//...

}

catch( Exception e) {

e.printStackTrace();

}finally {

if (cstmt != null)

cstmt.close();

}

//call procedure TEST_PKG.REC_PROC

try {

cstmt = conn.prepareCall("{ call TEST_PKG.REC_PROC(?,?) }");

//PLSQL RECORD type binding

Struct struct = conn.createStruct("TEST_PKG.R_TYP", new Object[]{12345,

"B"});

cstmt.setObject(1, struct);

cstmt.registerOutParameter(2, Types.STRUCT, "TEST_PKG.R_TYP");

cstmt.execute();

//get PLSQL RECORD type out parameter value

Struct outStruct = (Struct)cstmt.getObject(2);

//...

}

catch( Exception e) {

e.printStackTrace();

}finally {

if (cstmt != null)

cstmt.close();

}

if (conn != null)

Appendix A

About Using PL/SQL Types

A-8

conn.close();

System.out.println("done!");

}

Creating Java level objects for each row using %ROWTYPE Attribute

You can create Java-level objects using the

%ROWTYPE

attribute. In this case, each row of the

table is created as a

java.sql.Struct

object. For example, if you have a package

pack1

with

the following specification:

See Also:

Oracle Database PL/SQL Language Reference for more information about the

%ROWTYPE

attribute

CREATE OR REPLACE PACKAGE PACK1 AS

TYPE EMPLOYEE_ROWTYPE_ARRAY IS TABLE OF EMPLOYEES%ROWTYPE;

END PACK1;

The following code snippet shows how you can retrieve the value of the

EMPLOYEE_ROWTYPE_ARRAY

array using JDBC APIs:

This example returns a

java.sql.Array

java.sql.Struct

objects, where every

Struct

element represents one row of the

EMPLOYEES

table.

Example A-1 Creating Struct Objects for Database Table Rows

CallableStatement cstmt = conn.prepareCall("BEGIN SELECT * BULK COLLECT INTO :1 FROM

EMPLOYEE; END;");

cstmt.registerOutParameter(1,OracleTypes.ARRAY, "PACK1.EMPLOYEE_ROWTYPE_ARRAY");

cstmt.execute();

Array a = cstmt.getArray(1);

A.4 Using Embedded JDBC Escape Syntax

Oracle JDBC drivers support some embedded JDBC escape syntax, which is the syntax that

you specify between curly braces. The current support is basic.

Note:

JDBC escape syntax was previously known as SQL92 Syntax or SQL92 escape

syntax.

This section describes the support offered by the drivers for the following constructs:

• Time and Date Literals

• Scalar Functions

• LIKE Escape Characters

Appendix A

Using Embedded JDBC Escape Syntax

A-9

• MATCH_RECOGNIZE Clause

• Outer Joins

• Function Call Syntax

Where driver support is limited, these sections also describe possible workarounds.

Disabling Escape Processing

The processing for JDBC escape syntax is enabled by default, which results in the

JDBC driver performing escape substitution before sending the SQL code to the

database. If you want the driver to use regular Oracle SQL syntax, which is more

efficient than JDBC escape syntax processing, then use this statement:

stmt.setEscapeProcessing(false);

A.4.1 Time and Date Literals

Databases differ in the syntax they use for date, time, and timestamp literals. JDBC

supports dates and times written only in a specific format. This section describes the

formats you must use for date, time, and timestamp literals in SQL statements.

A.4.1.1 Date Literals

The JDBC drivers support date literals in SQL statements written in the format:

{d 'yyyy-mm-dd'}

Where

yyyy-mm-dd

represents the year, month, and day. For example:

{d '1995-10-22'}

The JDBC drivers will replace this escape clause with the equivalent Oracle

representation: "22 OCT 1995".

The following code snippet contains an example of using a date literal in a SQL

statement.

// Connect to the database

// You can put a database name after the @ sign in the connection URL.

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:oci:@");

ods.setUser("HR");

ods.setPassword("hr");

Connection conn = ods.getConnection();

// Create a Statement

Statement stmt = conn.createStatement ();

// Select the first name column from the employees table where the hire date is

Jan-23-1982

ResultSet rset = stmt.executeQuery

("SELECT first_name FROM employees WHERE hire_date = {d

'1982-01-23'}");

// Iterate through the result and print the employee names

while (rset.next ())

System.out.println (rset.getString (1));

Appendix A

Using Embedded JDBC Escape Syntax

A-10

A.4.1.2 Time Literals

The JDBC drivers support time literals in SQL statements written in the format:

{t 'hh:mm:ss'}

where,

hh:mm:ss

represents the hours, minutes, and seconds. For example:

{t '05:10:45'}

The JDBC drivers will replace this escape clause with the equivalent Oracle representation:

"05:10:45".

If the time is specified as:

{t '14:20:50'}

Then the equivalent Oracle representation would be "14:20:50", assuming the server is using

a 24-hour clock.

This code snippet contains an example of using a time literal in a SQL statement.

ResultSet rset = stmt.executeQuery

("SELECT first_name FROM employees WHERE hire_date = {t '12:00:00'}");

A.4.1.3 Timestamp Literals

The JDBC drivers support timestamp literals in SQL statements written in the format:

{ts 'yyyy-mm-dd hh:mm:ss.f...'}

where

yyyy-mm-dd hh:mm:ss.f...

represents the year, month, day, hours, minutes, and

seconds. The fractional seconds portion (

.f...

) is optional and can be omitted. For example:

{ts '1997-11-01 13:22:45'}

represents, in Oracle format, NOV 01 1997 13:22:45.

This code snippet contains an example of using a timestamp literal in a SQL statement.

ResultSet rset = stmt.executeQuery

("SELECT first_name FROM employees WHERE hire_date = {ts '1982-01-23 12:00:00'}");

Mapping SQL DATE Data type to Java

Oracle Database 8i and earlier versions did not support

TIMESTAMP

data, but Oracle

DATE

data

used to have a time component as an extension to the SQL standard. So, Oracle Database 8i

and earlier versions of JDBC drivers mapped

oracle.sql.DATE

java.sql.Timestamp

preserve the time component. Starting with Oracle Database 9.0.1,

TIMESTAMP

support was

included and 9i JDBC drivers started mapping

oracle.sql.DATE

java.sql.Date

. This

mapping was incorrect as it truncated the time component of Oracle

DATE

data. To overcome

this problem, Oracle Database 11g Release 1 introduced a new flag

mapDateToTimestamp

The default value of this flag is

true

, which means that by default the drivers will correctly

map

oracle.sql.DATE

java.sql.Timestamp

, retaining the time information. If you still want

the incorrect but 10g compatible

oracle.sql.DATE

java.sql.Date

mapping, then you can

get it by setting the value of

mapDateToTimestamp

flag to

false

Appendix A

Using Embedded JDBC Escape Syntax

A-11

Note:

• Since Oracle Database 11g, if you have an index on a DATE column to

be used by a SQL query, then to obtain faster and accurate results, you

must use the

setObject

method in the following way:

Date d = parseIsoDate(val);

Timestamp t = new Timestamp(d.getTime());

stmt.setObject(pos, new oracle.sql.DATE(t,

(Calendar)UTC_CAL.clone()));

This is because if you use the

setDate

method, then the time component

of the Oracle DATE data will be lost and if you use the

setTimestamp

method, then the index on the DATE column will not be used.

• To overcome the problem of

oracle.sql.DATE

java.sql.Date

mapping, Oracle Database 9.2 introduced a flag,

V8Compatible

. The

default value of this flag was

false

, which allowed the mapping of Oracle

DATE

data to

java.sql.Date

data. But, users could retain the time

component of the Oracle

DATE

data by setting the value of this flag to

true

. This flag is desupported since 11g because it controlled Oracle

Database 8i compatibility, which is no longer supported.

A.4.2 Scalar Functions

Oracle JDBC drivers do not support all scalar functions. To find out which functions the

drivers support, use the following methods supported by the Oracle-specific

oracle.jdbc.OracleDatabaseMetaData

class and the standard Java

java.sql.DatabaseMetadata

interface:

•

getNumericFunctions()

Returns a comma-delimited list of math functions supported by the driver. For

example,

ABS

COS

SQRT

•

getStringFunctions()

Returns a comma-delimited list of string functions supported by the driver. For

example,

ASCII

LOCATE

•

getSystemFunctions()

Returns a comma-delimited list of system functions supported by the driver. For

example,

DATABASE

USER

•

getTimeDateFunctions()

Returns a comma-delimited list of time and date functions supported by the driver.

For example,

CURDATE

DAYOFYEAR

HOUR

Note:

Oracle JDBC drivers support

, the function keyword.

Appendix A

Using Embedded JDBC Escape Syntax

A-12

A.4.3 LIKE Escape Characters

The characters

and

have special meaning in SQL

clauses. You use

to match zero

or more characters and

to match exactly one character. If you want to interpret these

characters literally in strings, then you precede them with a special escape character. For

example, if you want to use ampersand (

) as the escape character, then you identify it in the

SQL statement as:

Statement stmt = conn.createStatement ();

// Select the empno column from the emp table where the ename starts with '_'

ResultSet rset = stmt.executeQuery

("SELECT empno FROM emp WHERE ename LIKE '&_%' {ESCAPE '&'}");

// Iterate through the result and print the employee numbers

while (rset.next ())

System.out.println (rset.getString (1));

Note:

If you want to use the backslash character (\) as an escape character, then you

must enter it twice, that is, \\. For example:

ResultSet rset = stmt.executeQuery("SELECT empno FROM emp

WHERE ename LIKE '\\_%' {escape '\\'}");

A.4.4 MATCH_RECOGNIZE Clause

The

character is used as a token in

MATCH_RECOGNIZE

clause in Oracle Database 11g and

later versions. As the JDBC standard defines the

character as a parameter marker, the

JDBC Driver and the Server SQL Engine cannot distinguish between different uses of the

same token.

In earlier versions of JDBC Driver, if you want to interpret the

character as a

MATCH_RECOGNIZE

token and not as a parameter marker, then you must use a

Statement

instead of a

PreparedStatement

and disable escape processing. However, starting from

Oracle Database 12c Release 1 (12.1.0.2), you can use the '

{\\ ... \\}'

syntax while

using the

character, so that the JDBC driver does not process it as a parameter marker and

allows the SQL engine to process it. The following code snippet shows how to use the '

\ ... \\}'

syntax:

String sql =

"select T.firstW, T.lastZ, ? " + // use of parameter marker

"from tkpattern_S11 " +

"MATCH_RECOGNIZE ( " +

" MEASURES A.c1 as firstW, last(Z.c1) as lastZ " +

" ALL MATCHES " +

" {\\ PATTERN(A? X*? Y+? Z??)\\} " + // use of escape sequence

" DEFINE " +

" X as X.c2 > prev(X.c2), " +

" Y as Y.c2 < prev(Y.c2), " +

" Z as Z.c2 > prev(Z.c2)" +

") as T";

Appendix A

Using Embedded JDBC Escape Syntax

A-13

PreparedStatement ps = conn.prepareStatatement(sql);

ps.setString(1, "test");

ResultSet rs = ps.executeQuery();

Related Topics

• Using Embedded JDBC Escape Syntax

A.4.5 Outer Joins

Oracle JDBC drivers do not support the outer join syntax. The workaround is to use

Oracle outer join syntax:

Instead of:

Statement stmt = conn.createStatement ();

ResultSet rset = stmt.executeQuery

("SELECT ename, dname

FROM {OJ dept LEFT OUTER JOIN emp ON dept.deptno = emp.deptno}

ORDER BY ename");

Use Oracle SQL syntax:

Statement stmt = conn.createStatement ();

ResultSet rset = stmt.executeQuery

("SELECT ename, dname

FROM emp b, dept a WHERE a.deptno = b.deptno(+)

ORDER BY ename");

A.4.6 Function Call Syntax

Oracle JDBC drivers support the following procedure and function call syntax:

Procedure calls:

{ call procedure_name (argument1, argument2,...) }

Function calls:

{ ? = call procedure_name (argument1, argument2,...) }

A.4.7 JDBC Escape Syntax to Oracle SQL Syntax Example

You can write a simple program to translate JDBC escape syntax to Oracle SQL

syntax. The following program prints the comparable Oracle SQL syntax for

statements using JDBC escape syntax for function calls, date literals, time literals, and

timestamp literals. In the program, the

oracle.jdbc.OracleSql

class

parse()

method

performs the conversions.

public class Foo

{

static oracle.jdbc.OracleDriver driver = new oracle.jdbc.OracleDriver();

public static void main (String args[]) throws Exception

{

show ("{call foo(?, ?)}");

show ("{? = call bar (?, ?)}");

show ("{d '1998-10-22'}");

show ("{t '16:22:34'}");

show ("{ts '1998-10-22 16:22:34'}");

Appendix A

Using Embedded JDBC Escape Syntax

A-14

}

public static void show (String s) throws Exception

{

System.out.println (s + " => " +

driver.processSqlEscapes(s));

}

The following code is the output that prints the comparable SQL syntax.

{call foo(?, ?)} => BEGIN foo(:1, :2); END;

{? = call bar (?, ?)} => BEGIN :1 := bar (:2, :3); END;

{d '1998-10-22'} => TO_DATE ('1998-10-22', 'YYYY-MM-DD')

{t '16:22:34'} => TO_DATE ('16:22:34', 'HH24:MI:SS')

{ts '1998-10-22 16:22:34'} => TO_TIMESTAMP ('1998-10-22 16:22:34', 'YYYY-MM-DD

HH24:MI:SS.FF')

A.5 Oracle JDBC Notes and Limitations

The following limitations exist in the Oracle JDBC implementation, but all of them are either

insignificant or have easy workarounds. This section covers the following topics:

• CursorName

• JDBC Outer Join Escapes

• IEEE 754 Floating Point Compliance

• Catalog Arguments to DatabaseMetaData Calls

• SQLWarning Class

• Executing DDL Statements

• Binding Named Parameters

A.5.1 CursorName

Oracle JDBC drivers do not support the

getCursorName

and

setCursorName

methods,

because there is no convenient way to map them to Oracle constructs. Oracle recommends

using

ROWID

instead.

Related Topics

• Oracle ROWID Type

A.5.2 JDBC Outer Join Escapes

Oracle JDBC drivers do not support JDBC outer join escapes. Use Oracle SQL syntax with +

instead.

Related Topics

• Using Embedded JDBC Escape Syntax

Appendix A

Oracle JDBC Notes and Limitations

A-15

A.5.3 IEEE 754 Floating Point Compliance

The arithmetic for the Oracle

NUMBER

type does not comply with the IEEE 754 standard

for floating-point arithmetic. Therefore, there can be small disagreements between the

results of computations performed by Oracle and the same computations performed

by Java.

Oracle stores numbers in a format compatible with decimal arithmetic and guarantees

38 decimal digits of precision. It represents zero, minus infinity, and plus infinity

exactly. For each positive number it represents, it represents a negative number of the

same absolute value.

It represents every positive number between 10

-30

and (1 – 10

-38

) * 10

126

to full 38-digit

precision.

A.5.4 Catalog Arguments to DatabaseMetaData Calls

Certain

DatabaseMetaData

methods define a

catalog

parameter. This parameter is

one of the selection criteria for the method. Oracle does not have multiple catalogs,

but it does have packages.

Related Topics

• About Reporting DatabaseMetaData TABLE_REMARKS

A.5.5 SQLWarning Class

The

java.sql.SQLWarning

class provides information about a database access

warning. Warnings typically contain a description of the warning and a code that

identifies the warning. Warnings are silently chained to the object whose method

caused it to be reported. Oracle JDBC drivers generally do not support

SQLWarning

. As

an exception to this, scrollable result set operations do generate SQL warnings, but

the

SQLWarning

instance is created on the client, not in the database.

Related Topics

• About Processing SQL Exceptions

A.5.6 Executing DDL Statements

You must execute Data Definition Language (DDL) statements with

Statement

objects.

If you use

PreparedStatements

objects or

CallableStatements

objects, then the DDL

statement takes effect only on the first execution. This can cause unexpected behavior

if the SQL statements are in a statement cache.

A.5.7 Binding Named Parameters

Binding by name is not supported when using the

setXXX

methods. Under certain

circumstances, previous versions of Oracle JDBC drivers have allowed binding

statement variables by name when using the

setXXX

methods. In the following

statement, the named variable

EmpId

would be bound to the integer

314159

Appendix A

Oracle JDBC Notes and Limitations

A-16

PreparedStatement p = conn.prepareStatement

("SELECT name FROM emp WHERE id = :EmpId");

p.setInt(1, 314159);

This capability to bind by name using the

setXXX

methods is not part of the JDBC

specification, and Oracle does not support it. The JDBC drivers can throw a

SQLException

produce unexpected results. Starting from Oracle Database 10g JDBC drivers, bind by name

is supported using the

setXXXAtName

methods.

The bound values are not copied by the drivers until you call the

execute

method. So,

changing the bound value before calling the

execute

method could change the bound value.

For example, consider the following code snippet:

PreparedStatement p;

.......

Date d = new Date(1181676033917L);

p.setDate(1, d);

d.setTime(0);

p.executeUpdate();

This code snippet inserts

Date(0)

in the database instead of

Date(1181676033917L)

because

the bound values are not copied by JDBC driver implementation for performance reasons.

Related Topics

• Interface oracle.jdbc.OracleCallableStatement

• Interface oracle.jdbc.OraclePreparedStatement

Appendix A

Oracle JDBC Notes and Limitations

A-17

Oracle RAC Fast Application Notification

Starting from Oracle Database 12c Release 1 (12.1), the Oracle RAC Fast Application

Notification (FAN) APIs provide an alternative for taking advantage of the high-availability

(HA) features of Oracle Database, if you do not use Universal Connection Pool or Oracle

WebLogic Server with Active Grid Link (AGL).

This appendix covers the following topics:

• Overview of Oracle RAC Fast Application Notification

• Installing and Configuring Oracle RAC Fast Application Notification

• Using Oracle RAC Fast Application Notification

• Implementing a Connection Pool

This feature depends on the Oracle Notification System (ONS) message transport

mechanism. This feature requires configuring your system, servers, and clients to use ONS.

For using Oracle RAC Fast Application Notification, the

simplefan.jar

file must be present in

the

CLASSPATH

, and either the

ons.jar

file must be present in the

CLASSPATH

or an Oracle

Notification Services (ONS) client must be installed and running in the client system.

B.1 Overview of Oracle RAC Fast Application Notification

The Oracle RAC Fast Application Notification (FAN) feature provides a simplified API for

accessing FAN events through a callback mechanism. This mechanism enables third-party

drivers, connection pools, and containers to subscribe, receive and process FAN events.

These APIs are referred to as Oracle RAC FAN APIs in this appendix.

The Oracle RAC FAN APIs provide FAN event notification for developing more responsive

applications that can take full advantage of Oracle Database HA features. If you do not want

to use Universal Connection Pool, but want to work with FAN events implementing your own

connection pool, then you should use Oracle RAC Fast Application Notification.

Note:

• If you do not want to implement your own connection pool, then you should use

Oracle Universal Connection Pool to get all the advantages of Oracle RAC Fast

Application Notification, along with many additional benefits.

• Starting from Oracle Database 12c Release 1 (12.1), implicit connection cache

(ICC) is desupported. Oracle recommends to use Universal Connection Pool

instead.

Your applications are enabled to respond to FAN events in the following way:

• Listening for Oracle RAC service down and node down events.

B-1

• Listening for Oracle RAC service up events representing any Oracle RAC or

Global data Service (GDS) start or restart. For these UP events, FAN parameter

status is

and

event_type

is one of the following:

database

instance

service

servicemember

• Supporting FAN ONS event syntax and fields for both Oracle Database Release

12c and earlier releases, for example, the

event_type

and

timezone

fields added

to every event, the

db_domain

field added to every event other than node or public-

network events, the

percentf

field added to Run-Time Load Balancing (RLB)

events, and so on.

• Listening for load balancing advisory events and responding to them.

This feature exposes the FAN events, which are the notifications sent by a cluster

running Oracle RAC, to inform the subscribers about an event happening at the

service level or the node level. The supported FAN events are the following:

• Service up

The service up event notifies the connection pool that a new instance is available

for use, allowing sessions to be created on the new instance. The

ServiceUpEvent

Client API is supported in the current release of the Oracle RAC FAN APIs, that is,

in the

simplefan.jar

file.

• Service down

The service down events notify that the managed resources are down and

currently not available for access. There are two types of service down events:

– Events indicating that a particular instance of a service is down and the

instance is no longer able to accept work.

– Events indicating that all-but-one instances of a service are down and the

service is no longer able to accept work.

• Node down

The node down events notify that the Oracle RAC node identified by the host

identifier is down and not reachable. The cluster sends node down events when a

node is no longer able to accept work.

• Planned down

Planned down events include all the down events, except node down event. These

events have the following two fields set:

status=down

and

reason=user

• Load balancing advisory

The load balancing advisory events provide metrics for load balancing algorithms.

Load balancing advisories are sent regularly to inform subscribers of the

recommended distribution of work among the available nodes.

Note:

If you want to implement your own connection pool, only then you should use

Oracle RAC Fast Application Notification. Otherwise, you should use Oracle

Universal Connection Pool to get all the advantages of Oracle RAC Fast

Application Notification, along with many additional benefits.

Appendix B

Overview of Oracle RAC Fast Application Notification

B-2

Related Topics

• Oracle Universal Connection Pool Developer’s Guide

B.2 Installing and Configuring Oracle RAC Fast Application

Notification

You can install the Oracle RAC FAN APIs by performing the following steps:

1. Download the

simplefan.jar

file from the following link

JDBC and UCP Downloads page

2. Add the

simplefan.jar

file to the classpath.

3. Perform the following in your Java code:

a. Get an instance of the

FanManager

class by using the

getInstance

method.

b. Configure the event daemon using the

configure

method of the

FanManager

class.

The

configure

method sets the following properties:

onsNodes

: A comma separated list of

host:port

pairs of ONS daemons that the ONS

runtime in this Java VM should communicate with. The

host

in a

host:port

pair is

the host name of a system running the ONS daemon. The

port

is the local port

configuration parameter for that daemon.

onsWalletFile

: The path name of the ONS wallet file. The wallet file is the path to a

local wallet file used by SSL to store SSL certificates. Same as wallet file

configuration parameter to ONS daemon.

onsWalletPassword

: The password for accessing the ONS wallet file.

See Also:

• For a detailed description of the Oracle RAC FAN APIs, refer to Oracle

Database RAC FAN Events Java API Reference.

• Oracle Universal Connection Pool Developer’s Guide

B.3 Using Oracle RAC Fast Application Notification

The following code snippet explains how to handle FAN down events. This example code

prints the event data to the standard output device.

This example code demonstrates how to use Oracle RAC FAN APIs by overloading the

handleFanEvent

method to accept different FAN event notifications as arguments. The

example code also displays event data such as:

• Name of the system sending the FAN event notification

• Timestamp of the FAN event notification

• Load status of the FAN event notification

Appendix B

Installing and Configuring Oracle RAC Fast Application Notification

B-3

Example B-1 Example of Sample Code Using Oracle RAC FAN API for FAN

Down Events

...

...Properties props = new Properties();

props.putProperty(“serviceName", “gl");

FanSubscription sub = FanManager.getInstance().subscribe(props);

sub.addListener(new FanEventListener()) {

public void handleFanEvent(ServiceDownEvent se) {

try {

System.out.println(event.getTimestamp());

System.out.println(event.getServiceName());

System.out.println(event.getDatabaseUniqueName());

System.out.println(event.getReason());

ServiceMemberEvent me = se.getServiceMemberEvent();

if (me != null) {

System.out.println(me.getInstanceName());

System.out.println(me.getNodeName());

System.out.println(me.getServiceMemberStatus());

}

ServiceCompositeEvent ce = se.getServiceCompositeEvent();

if (ce != null) {

System.out.println(ce.getServiceCompositeStatus());

}

catch (Throwable t) {

// handle all exceptions and errors

t.printStackTrace(System.err);

}

public void handleFanEvent(NodeDownEvent ne) {

try {

System.out.println(event.getTimestamp());

System.out.println(ne.getNodeName());

System.out.println(ne.getIncarnation());

}

catch (Throwable t) {

// handle all exceptions and errors

t.printStackTrace(System.err);

}

public void handleFanEvent(LoadAdvisoryEvent le) {

try {

System.out.println(event.getTimestamp());

System.out.println(le.getServiceName());

System.out.println(le.getDatabaseUniqueName());

System.out.println(le.getInstanceName());

System.out.println(le.getPercent());

System.out.println(le.getServiceQuality());

System.out.println(le.getLoadStatus());

}

catch (Throwable t) {

// handle all exceptions and errors

t.printStackTrace(System.err);

}

});

Appendix B

Using Oracle RAC Fast Application Notification

B-4

Example B-2 Example of Sample Code Using Oracle RAC FAN API for FAN Up Events

The following code snippet explains how to use Oracle RAC Fast Application Notification for

service up events. The code uses the new Oracle RAC FAN APIs introduced in Oracle

Database 12c Release 2 (12.2.0.1), namely,

FanUpEventListener

interface that extends the

FanEventListener

interface and

ServiceUpEvent

. You must implement the

FanUpEventListener

interface in the client application in the similar way you implement the

FanEventListener

interface.

import oracle.simplefan.*;

...

FanEventListener fanListener = new FanUpEventListener() {

public void handleEvent(ServiceUpEvent event) { ...... }

// Specify the next action here, when the node comes up

public void handleEvent(NodeUpEvent event) { ...... }

......

}

FanManager fanMngr = FanManager.getInstance();

Properties onsProps = new Properties();

onsProps.setProperty("onsNodes", ......);

fanMngr.configure(onsProps);

Properties subscriptionProps = new Properties();

subscriptionProps.setProperty("serviceName", ......);

fanSubscription = fanMngr.subscribe(subscriptionProps);

fanSubscription.addListener(fanListener);

...

B.4 Implementing a Connection Pool

You must implement your own connection pool for using Oracle RAC FAN APIs. Consider the

following points before you implement a connection pool using the Oracle RAC FAN APIs:

• Oracle RAC FAN APIs provide a subset of FAN events.

• Oracle RAC FAN APIs support only ONS events. If you want your application to support

corresponding supercluster events, then you may require additions to the subscription

properties.

Appendix B

Implementing a Connection Pool

B-5

JDBC Coding Tips

This appendix describes methods to optimize a Java Database Connectivity (JDBC)

application. It includes the following topics:

• JDBC and Multithreading

• Performance Optimization of JDBC Programs

• Transaction Isolation Levels and Access Modes in JDBC

C.1 JDBC and Multithreading

Oracle JDBC drivers provide full support for, and are highly optimized for, applications that

use Java multithreading. Controlled serial access to a connection, such as that provided by

connection caching, is both necessary and encouraged. However, Oracle strongly

discourages sharing a database connection among multiple threads. Avoid allowing multiple

threads to access a connection simultaneously. If multiple threads must share a connection,

use a disciplined begin-using/end-using protocol.

Keep the following points in mind while working on multithreaded applications:

• Use the

Connection

object as a local variable.

• Close the connection in the

finally

block before exiting the method. For example:

Connection conn = null;

try

{

...

}

finally

{

if(conn != null) conn.close();

}

• Do not share

Connection

objects between threads.

• Never synchronize on JDBC objects because it is done internally by the driver.

• Use the

Statement.setQueryTimeout

method to set the time to execute a query instead

of cancelling the long-running query from a different thread.

• Use the

Statement.cancel

method for SQL operations like

SELECT

UPDATE

, or

DELETE

• Use the

Connection.cancel

method for SQL operations like

COMMIT

ROLLBACK

, and so

on.

• Do not use the

Thread.interrupt

method.

C.2 Performance Optimization of JDBC Programs

You can significantly enhance the performance of your JDBC programs by using any of these

features:

C-1

• Disabling Auto-Commit Mode

• Standard Fetch Size and Oracle Row Prefetching

• About Setting the Session Data Unit Size

• JDBC Update Batching

• Statement Caching

• Mapping Between Built-in SQL and Java Types

C.2.1 Disabling Auto-Commit Mode

Auto-commit mode indicates to the database whether to issue an automatic

COMMIT

operation after every SQL operation. Being in auto-commit mode can be expensive in

terms of time and processing effort if, for example, you are repeating the same

statement with different bind variables.

By default, new connection objects are in auto-commit mode. However, you can

disable auto-commit mode with the

setAutoCommit

method of the connection object,

either

java.sql.Conection

oracle.jdbc.OracleConnection

In auto-commit mode, the

COMMIT

operation occurs either when the statement

completes or the next execute occurs, whichever comes first. In the case of

statements returning a

ResultSet

object, the statement completes when the last row

of the Result Set has been retrieved or when the Result Set has been closed. In more

complex cases, a single statement can return multiple results as well as output

parameter values. Here, the

COMMIT

occurs when all results and output parameter

values have been retrieved.

If you disable auto-commit mode with a

setAutoCommit(false)

call, then you must

manually commit or roll back groups of operations using the

commit

rollback

method of the connection object.

Example

The following example illustrates loading the driver and connecting to the database.

Because new connections are in auto-commit mode by default, this example shows

how to disable auto-commit. In the example,

conn

represents the

Connection

object,

and

stmt

represents the

Statement

object.

// Connect to the database

// You can put a database host name after the @ sign in the connection URL.

OracleDataSource ods = new OracleDataSource();

ods.setURL("jdbc:oracle:oci:@");

ods.setUser("HR");

ods.setPassword("hr");

Connection conn = ods.getConnection();

// It's faster when auto commit is off

conn.setAutoCommit (false);

// Create a Statement

Statement stmt = conn.createStatement ();

...

Appendix C

Performance Optimization of JDBC Programs

C-2

C.2.2 Standard Fetch Size and Oracle Row Prefetching

Oracle JDBC connection and statement objects allow you to specify the number of rows to

prefetch into the client with each trip to the database while a result set is being populated

during a query. You can set a value in a connection object that affects each statement

produced through that connection, and you can override that value in any particular

statement object. The default value in a connection object is 10. Prefetching data into the

client reduces the number of round-trips to the server.

Similarly, and with more flexibility, JDBC 2.0 enables you to specify the number of rows to

fetch with each trip, both for statement objects (affecting subsequent queries) and for result

set objects (affecting row refetches). By default, a result set uses the value for the statement

object that produced it. If you do not set the JDBC 2.0 fetch size, then the Oracle connection

row-prefetch value is used by default.

Related Topics

• Row Fetch Size

C.2.3 About Setting the Session Data Unit Size

Session data unit (SDU) is a buffer that Oracle Net uses to place data before transmitting it

across the network. Oracle Net sends the data in the buffer either when the request is

completed or when it is full.

You can configure the SDU and obtain the following benefits, among others:

• Reduction in the time required to transmit a SQL query and result across the network

• Transmission of larger chunks of data

Note:

The footprint of the client and the server process increase if you set a bigger SDU

size.

See Also:

Oracle Database Net Services Administrator's Guide

This section describes the following:

• About Setting the SDU Size for the Database Server

• About Setting the SDU Size for JDBC Thin Client

C.2.3.1 About Setting the SDU Size for the Database Server

To set the SDU size for the database server, configure the

DEFAULT_SDU_SIZE

parameter in

the

sqlnet.ora

file.

Appendix C

Performance Optimization of JDBC Programs

C-3

C.2.3.2 About Setting the SDU Size for JDBC OCI Client

The JDBC OCI client uses Oracle Net layer. So, you can set the SDU size for the

JDBC OCI client by configuring the

DEFAULT_SDU_SIZE

parameter in the

sqlnet.ora

file.

C.2.3.3 About Setting the SDU Size for JDBC Thin Client

You can set the SDU size for JDBC thin client by specifying it in the

DESCRIPTION

parameter for a particular connection descriptor.

sales.example.com=

(DESCRIPTION=

(SDU=11280)

(ADDRESS=(PROTOCOL=tcp)(HOST=sales-server)(PORT=5221))

(CONNECT_DATA=

(SERVICE_NAME=sales.example.com))

)

C.2.4 JDBC Update Batching

Oracle JDBC drivers enable you to accumulate

INSERT

DELETE

, and

UPDATE

operations

of prepared statements at the client and send them to the server in batches. This

feature reduces round-trips to the server.

Note:

Oracle recommends to keep the batch sizes in the range of 100 or less.

Larger batches provide little or no performance improvement and may

actually reduce performance due to the client resources required to handle

the large batch.

C.2.5 Statement Caching

Statement caching improves performance by caching executable statements that are

used repeatedly, such as in a loop or in a method that is called repeatedly.

Applications use the statement cache to cache statements associated with a particular

physical connection. When you enable Statement caching, a Statement object is

cached when you call the

method. Because each physical connection has its

own cache, multiple caches can exist if you enable Statement caching for multiple

physical connections.

Note:

The Oracle JDBC drivers are optimized for use with the Oracle Statement

cache. Oracle strongly recommends that you use the Oracle Statement

cache (implicit or explicit).

Appendix C

Performance Optimization of JDBC Programs

C-4

When you enable Statement caching on a connection cache, the logical connections benefit

from the Statement caching that is enabled on the underlying physical connection. If you try

to enable Statement caching on a logical connection held by a connection cache, then this

will throw an exception.

Related Topics

• Statement and Result Set Caching

C.2.6 Mapping Between Built-in SQL and Java Types

The SQL built-in types are those types with system-defined names, such as

NUMBER

, and

CHAR

, as opposed to the Oracle objects, varray, and nested table types, which have user-

defined names. In JDBC programs that access data of built-in SQL types, all type

conversions are unambiguous, because the program context determines the Java type to

which a SQL datum will be converted.

Table C-1 Mapping of SQL Data Types to Java Classes that Represent SQL Data

Types

SQL Data Type ORACLE Mapping - Java Classes Representing SQL Data Types

CHAR oracle.sql.CHAR

VARCHAR2 oracle.sql.CHAR

DATE oracle.sql.DATE

DECIMAL oracle.sql.NUMBER

DOUBLE PRECISION oracle.sql.NUMBER

FLOAT oracle.sql.NUMBER

INTEGER oracle.sql.NUMBER

REAL oracle.sql.NUMBER

RAW oracle.sql.RAW

LONG RAW oracle.sql.RAW

REF CURSOR java.sql.ResultSet

CLOB LOCATOR oracle.jdbc.OracleClob

BLOB LOCATOR oracle.jdbc.OracleBlob

BFILE oracle.sql.BFILE

nested table

oracle.jdbc.OracleArray

varray

oracle.jdbc.OracleArray

SQL object value If there is no entry for the object value in the type map:

•

oracle.jdbc.OracleStruct

If there is an entry for the object value in the type map:

• customized Java class

REF to SQL object type class that implements

oracle.sql.SQLRef

, typically by implementing

oracle.jdbc.OracleRef

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.CLOB

class is deprecated and replaced

with the

oracle.jdbc.OracleClob

interface.

Appendix C

Performance Optimization of JDBC Programs

C-5

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.BLOB

class is deprecated and

replaced with the

oracle.jdbc.OracleBlob

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.ARRAY

class is deprecated and

replaced with the

oracle.jdbc.OracleArray

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.STRUCT

class is deprecated

and replaced with the

oracle.jdbc.OracleStruct

interface.

Starting from Oracle Database 12c Release 1 (12.1), the

oracle.sql.REF

class is deprecated and

replaced with the

oracle.jdbc.OracleRef

interface.

The most efficient way to access numeric data is to use primitive Java types like

int

float

long

, and

double

. However, the range of values of these types do not exactly

match the range of values of the SQL

NUMBER

data type. As a result, there may be

some loss of information. If absolute precision is required across the entire value

range, then use the

BigDecimal

type.

All character data is converted to the UCS2 character set of Java. The most efficient

way to access character data is as

java.lang.String

. In worst case, this can cause a

loss of information when two or more characters in the database character set map to

a single UCS2 character. Since Oracle Database 11g, all characters in the character

set map to the characters in the UCS2 character set. However, some characters do

map to surrogate pairs.

C.3 Transaction Isolation Levels and Access Modes in

JDBC

Read-only connections are supported by Oracle JDBC drivers, but not by the Oracle

server.

For transactions, the Oracle server supports only the

TRANSACTION_READ_COMMITTED

and

TRANSACTION_SERIALIZABLE

transaction isolation levels. The default is

TRANSACTION_READ_COMMITTED

. Use the following methods of the

oracle.jdbc.OracleConnection

interface to get and set the level:

•

getTransactionIsolation

: Gets the current transaction isolation level of the

connection.

•

setTransactionIsolation

: Changes the transaction isolation level, using either

the

TRANSACTION_READ_COMMITTED

or the

TRANSACTION_SERIALIZABLE

value.

Appendix C

Transaction Isolation Levels and Access Modes in JDBC

C-6

JDBC Error Messages

This appendix briefly discusses the general structure of Java Database Connectivity (JDBC)

error messages, then lists general JDBC error messages and TTC error messages that

Oracle JDBC drivers can return. The appendix is organized as follows:

• General Structure of JDBC Error Messages

• General JDBC Messages

• Native XA Messages

• TTC Messages

Each of the message lists is first sorted by

ORA

number, and then alphabetically.

D.1 General Structure of JDBC Error Messages

The general JDBC error message structure allows run-time information to be appended to the

end of a message, following a colon, as follows:

<error_message>:<extra_info>

For example, a "closed statement" error might be displayed as follows:

Closed Statement:next

This indicates that the exception was thrown during a call to the

method (of a result set

object).

In some cases, the user can find the same information in a stack trace.

D.2 General JDBC Messages

This section lists general JDBC error messages, first sorted by the

ORA

number, and then in

alphabetic order in the following subsections:

• JDBC Messages Sorted by ORA Number

• JDBC Messages Sorted in Alphabetic Order

Note:

The

ORA-17033

and

ORA-17034

error messages use the term SQL92. The JDBC

escape syntax was previously known as SQL92 Syntax or SQL92 escape syntax.

D.2.1 JDBC Messages Sorted by ORA Number

The following table lists the JDBC error messages sorted by the

ORA

number:

D-1

Table D-1 JDBC Messages Sorted by ORA Number

ORA Number Message

ORA-17001 Internal Error

ORA-17002 Io exception

ORA-17003 Invalid column index

ORA-17004 Invalid column type

ORA-17005 Unsupported column type

ORA-17006 Invalid column name

ORA-17007 Invalid dynamic column

ORA-17008 Closed Connection

ORA-17009 Closed Statement

ORA-17010 Closed Resultset

ORA-17011 Exhausted Resultset

ORA-17012 Parameter Type Conflict

ORA-17014 ResultSet.next was not called

ORA-17015 Statement was cancelled

ORA-17016 Statement timed out

ORA-17017 Cursor already initialized

ORA-17018 Invalid cursor

ORA-17019 Can only describe a query

ORA-17020 Invalid row prefetch

ORA-17021 Missing defines

ORA-17022 Missing defines at index

ORA-17023 Unsupported feature

ORA-17024 No data read

ORA-17025 Error in defines.isNull ()

ORA-17026 Numeric Overflow

ORA-17027 Stream has already been closed

ORA-17028 Can not do new defines until the current ResultSet is closed

ORA-17029 setReadOnly: Read-only connections not supported

ORA-17030 READ_COMMITTED and SERIALIZABLE are the only valid

transaction levels

ORA-17031 setAutoClose: Only support auto close mode on

ORA-17032 cannot set row prefetch to zero

ORA-17033 Malformed SQL92 string at position

ORA-17034 Non supported SQL92 token at position

ORA-17035 Character Set Not Supported !!

ORA-17036 exception in OracleNumber

ORA-17037 Fail to convert between UTF8 and UCS2

ORA-17038 Byte array not long enough

Appendix D

General JDBC Messages

D-2

Table D-1 (Cont.) JDBC Messages Sorted by ORA Number

ORA Number Message

ORA-17039 Char array not long enough

ORA-17040 Sub Protocol must be specified in connection URL

ORA-17041 Missing IN or OUT parameter at index:

ORA-17042 Invalid Batch Value

ORA-17043 Invalid stream maximum size

ORA-17044 Internal error: Data array not allocated

ORA-17045 Internal error: Attempt to access bind values beyond the batch

value

ORA-17046 Internal error: Invalid index for data access

ORA-17047 Error in Type Descriptor parse

ORA-17048 Undefined type

ORA-17049 Inconsistent java and sql object types

ORA-17050 no such element in vector

ORA-17051 This API cannot be be used for non-UDT types

ORA-17052 This ref is not valid

ORA-17053 The size is not valid

ORA-17054 The LOB locator is not valid

ORA-17055 Invalid character encountered in

ORA-17056 Non supported character set (add orai18n.jar in your classpath)

ORA-17057 Closed LOB

ORA-17058 Internal error: Invalid NLS Conversion ratio

ORA-17059 Fail to convert to internal representation

ORA-17060 Fail to construct descriptor

ORA-17061 Missing descriptor

ORA-17062 Ref cursor is invalid

ORA-17063 Not in a transaction

ORA-17064 Invalid Sytnax or Database name is null

ORA-17065 Conversion class is null

ORA-17066 Access layer specific implementation needed

ORA-17067 Invalid Oracle URL specified

ORA-17068 Invalid argument(s) in call

ORA-17069 Use explicit XA call

ORA-17070 Data size bigger than max size for this type

ORA-17071 Exceeded maximum VARRAY limit

ORA-17072 Inserted value too large for column

ORA-17074 invalid name pattern

ORA-17075 Invalid operation for forward only resultset

ORA-17076 Invalid operation for read only resultset

Appendix D

General JDBC Messages

D-3

Table D-1 (Cont.) JDBC Messages Sorted by ORA Number

ORA Number Message

ORA-17077 Fail to set REF value

ORA-17078 Cannot do the operation as connections are already opened

ORA-17079 User credentials doesn't match the existing ones

ORA-17080 invalid batch command

ORA-17081 error occurred during batching

ORA-17082 No current row

ORA-17083 Not on the insert row

ORA-17084 Called on the insert row

ORA-17085 Value conflicts occurs

ORA-17086 Undefined column value on the insert row

ORA-17087 Ignored performance hint: setFetchDirection()

ORA-17088 Unsupported syntax for requested resultset type and

concurrency level

ORA-17089 internal error

ORA-17090 operation not allowed

ORA-17091 Unable to create resultset at the requested type and/or

concurrency level

ORA-17092 JDBC statements cannot be created or executed at end of call

processing

ORA-17093 OCI operation returned OCI_SUCCESS_WITH_INFO

ORA-17094 Object type version mismatched

ORA-17095 Statement cache size has not been set

ORA-17096 Statement Caching cannot be enabled for this logical connection.

ORA-17097 Invalid PL/SQL Index Table element type

ORA-17098 Invalid empty lob operation

ORA-17099 Invalid PL/SQL Index Table array length

ORA-17100 Invalid database Java Object

ORA-17101 Invalid properties in OCI Connection Pool Object

ORA-17102 Bfile is read only

ORA-17103 invalid connection type to return via getConnection. Use

getJavaSqlConnection instead

ORA-17104 SQL statement to execute cannot be empty or null

ORA-17105 connection session time zone was not set

ORA-17106 invalid JDBC-OCI driver connection pool configuration specified

ORA-17107 invalid proxy type specified

ORA-17108 No max length specified in defineColumnType

ORA-17109 standard Java character encoding not found

ORA-17110 execution completed with warning

ORA-17111 Invalid connection cache TTL timeout specified

Appendix D

General JDBC Messages

D-4

Table D-1 (Cont.) JDBC Messages Sorted by ORA Number

ORA Number Message

ORA-17112 Invalid thread interval specified

ORA-17113 Thread interval value is more than the cache timeout value

ORA-17114 could not use local transaction commit in a global transaction

ORA-17115 could not use local transaction rollback in a global transaction

ORA-17116 could not turn on auto-commit in an active global transaction

ORA-17117 could not set savepoint in an active global transaction

ORA-17118 could not obtain ID for a named Savepoint

ORA-17119 could not obtain name for an un-named Savepoint

ORA-17120 could not set a Savepoint with auto-commit on

ORA-17121 could not rollback to a Savepoint with auto-commit on

ORA-17122 could not rollback to a local txn Savepoint in a global transaction

ORA-17123 Invalid statement cache size specified

ORA-17124 Invalid connection cache Inactivity timeout specified

ORA-17125 Improper statement type returned by explicit cache

ORA-17126 Fixed Wait timeout elapsed

ORA-17127 Invalid Fixed Wait timeout specified

ORA-17128 SQL string is not Query

ORA-17129 SQL string is not a DML Statement

ORA-17132 Invalid conversion requested

ORA-17133 UNUSED

ORA-17134 Length of named parameter in SQL exceeded 32 characters

ORA-17135 Parameter name used in setXXXStream appears more than

once in SQL

ORA-17136 Malformed DATALINK URL, try getString() instead

ORA-17137 Connection Caching Not Enabled or Not a Valid Cache Enabled

DataSource

ORA-17138 Invalid Connection Cache Name. Must be a valid String and

Unique

ORA-17139 Invalid Connection Cache Properties

ORA-17140 Connection Cache with this Cache Name already exists

ORA-17141 Connection Cache with this Cache Name does not exist

ORA-17142 Connection Cache with this Cache Name is Disabled

ORA-17143 Invalid or Stale Connection found in the Connection Cache

ORA-17144 statement handle not executed

ORA-17145 Invalid ONS Event received

ORA-17146 Invalid ONS Event Version received

ORA-17147 Attempt to set a parameter name that does not occur in the SQL

ORA-17148 Method only implemented in thin

ORA-17149 This is already a proxy session

Appendix D

General JDBC Messages

D-5

Table D-1 (Cont.) JDBC Messages Sorted by ORA Number

ORA Number Message

ORA-17150 Wrong arguments for proxy session

ORA-17151 Clob is too large to be stored in a Java String

ORA-17152 This method is only implemented in logical connections

ORA-17153 This method is only implemented in physical connections

ORA-17154 Cannot map Oracle character to Unicode

ORA-17155 Cannot map Unicode to Oracle character

ORA-17156 Invalid array size for End-to-End metrics values

ORA-17157 setString can only process strings of less than 32766

chararacters

ORA-17158 duration is invalid for this function

ORA-17159 metric value for end-to-end tracing is too long

ORA-17160 execution context id sequence number out of range

ORA-17161 Invalid transaction mode used

ORA-17162 Unsupported holdability value

ORA-17163 Can not use getXAConnection() when connection caching is

enabled

ORA-17164 Can not call getXAResource() from physical connection with

caching on

ORA-17165 DBMS_JDBC package not preset in server for this connection

ORA-17166 Cannot perform fetch on a PLSQL statement

ORA-17167 PKI classes not found. To use 'connect /' functionality,

oraclepki.jar must be in the classpath

ORA-17168 encountered a problem with the Secret Store. Check the wallet

location for the presence of an open wallet (cwallet.sso) and

ensure that this wallet contains the correct credentials using the

mkstore utility

ORA-17169 Cannot bind stream to a ScrollableResultSet or

UpdatableResultSet

ORA-17170 The Namespace cannot be empty

ORA-17171 The attribute length cannot exceed 30 chars

ORA-17172 That value of the attribute cannot exceed 400 chars

ORA-17173 Not all return parameters registered

ORA-17174 The only supported namespace is CLIENTCONTEXT

ORA-17175 Error during remote ONS configuration

ORA-17259 SQLXML cannot find the XML support jar file in the classpath

ORA-17260 Attempt to read an empty SQLXML

ORA-17261 Attempt to read a SQLXML that is not readable

ORA-17262 Attempt to write a SQLXML that is not writeable

ORA-17263 SQLXML cannot create a Result of that type

ORA_17264 SQLXML cannoct create a Source of that type

Appendix D

General JDBC Messages

D-6

D.2.2 JDBC Messages Sorted in Alphabetic Order

The following table lists the JDBC error messages sorted in alphabetic order:

Table D-2 JDBC Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17066 Access layer specific implementation needed

ORA-17261 Attempt to read a SQLXML that is not readable

ORA-17260 Attempt to read an empty SQLXML

ORA-17147 Attempt to set a parameter name that does not occur in the SQL

ORA-17262 Attempt to write a SQLXML that is not writeable

ORA-17102 Bfile is read only

ORA-17038 Byte array not long enough

ORA-17084 Called on the insert row

ORA-17164 Can not call getXAResource() from physical connection with caching

ORA-17028 Can not do new defines until the current ResultSet is closed

ORA-17163 Can not use getXAConnection() when connection caching is enabled

ORA-17019 Can only describe a query

ORA-17169 Cannot bind stream to a ScrollableResultSet or UpdatableResultSet

ORA-17078 Cannot do the operation as connections are already opened

ORA-17154 Cannot map Oracle character to Unicode

ORA-17155 Cannot map Unicode to Oracle character

ORA-17166 Cannot perform fetch on a PLSQL statement

ORA-17032 Cannot set row prefetch to zero

ORA-17039 Char array not long enough

ORA-17035 Character Set Not Supported !!

ORA-17151 Clob is too large to be stored in a Java String

ORA-17008 Closed Connection

ORA-17057 Closed LOB

ORA-17010 Closed Resultset

ORA-17009 Closed Statement

ORA-17140 Connection Cache with this Cache Name already exists

ORA-17141 Connection Cache with this Cache Name does not exist

ORA-17142 Connection Cache with this Cache Name is Disabled

ORA-17137 Connection Caching Not Enabled or Not a Valid Cache Enabled

DataSource

ORA-17105 Connection session time zone was not set

ORA-17065 Conversion class is null

ORA-17118 Could not obtain ID for a named Savepoint

ORA-17119 Could not obtain name for an un-named Savepoint

Appendix D

General JDBC Messages

D-7

Table D-2 (Cont.) JDBC Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17122 Could not rollback to a local txn Savepoint in a global transaction

ORA-17121 Could not rollback to a Savepoint with auto-commit on

ORA-17120 Could not set a Savepoint with auto-commit on

ORA-17117 Could not set savepoint in an active global transaction

ORA-17116 Could not turn on auto-commit in an active global transaction

ORA-17114 Could not use local transaction commit in a global transaction

ORA-17115 Could not use local transaction rollback in a global transaction

ORA-17017 Cursor already initialized

ORA-17070 Data size bigger than max size for this type

ORA-17165 DBMS_JDBC package not preset in server for this connection

ORA-17158 Duration is invalid for this function

ORA-17168 Encountered a problem with the Secret Store. Check the wallet

location for the presence of an open wallet (cwallet.sso) and ensure

that this wallet contains the correct credentials using the mkstore

utility

ORA-17175 Error during remote ONS configuration

ORA-17025 Error in defines.isNull ()

ORA-17047 Error in Type Descriptor parse

ORA-17081 error occurred during batching

ORA-17071 Exceeded maximum VARRAY limit

ORA-17036 Exception in OracleNumber

ORA-17110 Execution completed with warning

ORA-17160 Execution context id sequence number out of range

ORA-17011 Exhausted Resultset

ORA-17060 Fail to construct descriptor

ORA-17037 Fail to convert between UTF8 and UCS2

ORA-17059 Fail to convert to internal representation

ORA-17077 Fail to set REF value

ORA-17126 Fixed Wait timeout elapsed

ORA-17087 Ignored performance hint: setFetchDirection()

ORA-17125 Improper statement type returned by explicit cache

ORA-17049 Inconsistent java and sql object types

ORA-17072 Inserted value too large for column

ORA-17001 Internal Error

ORA-17089 internal error

ORA-17045 Internal error: Attempt to access bind values beyond the batch value

ORA-17044 Internal error: Data array not allocated

ORA-17046 Internal error: Invalid index for data access

ORA-17058 Internal error: Invalid NLS Conversion ratio

Appendix D

General JDBC Messages

D-8

Table D-2 (Cont.) JDBC Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17068 Invalid argument(s) in call

ORA-17156 Invalid array size for End-to-End metrics values

ORA-17080 invalid batch command

ORA-17042 Invalid Batch Value

ORA-17055 Invalid character encountered in

ORA-17003 Invalid column index

ORA-17006 Invalid column name

ORA-17004 Invalid column type

ORA-17124 Invalid connection cache Inactivity timeout specified

ORA-17138 Invalid Connection Cache Name. Must be a valid String and Unique

ORA-17139 Invalid Connection Cache Properties

ORA-17111 Invalid connection cache TTL timeout specified

ORA-17103 invalid connection type to return via getConnection. Use

getJavaSqlConnection instead

ORA-17132 Invalid conversion requested

ORA-17018 Invalid cursor

ORA-17100 Invalid database Java Object

ORA-17007 Invalid dynamic column

ORA-17098 Invalid empty lob operation

ORA-17127 Invalid Fixed Wait timeout specified

ORA-17106 invalid JDBC-OCI driver connection pool configuration specified

ORA-17074 invalid name pattern

ORA-17145 Invalid ONS Event received

ORA-17146 Invalid ONS Event Version received

ORA-17075 Invalid operation for forward only resultset

ORA-17076 Invalid operation for read only resultset

ORA-17143 Invalid or Stale Connection found in the Connection Cache

ORA-17067 Invalid Oracle URL specified

ORA-17099 Invalid PL/SQL Index Table array length

ORA-17097 Invalid PL/SQL Index Table element type

ORA-17101 Invalid properties in OCI Connection Pool Object

ORA-17107 invalid proxy type specified

ORA-17020 Invalid row prefetch

ORA-17123 Invalid statement cache size specified

ORA-17043 Invalid stream maximum size

ORA-17064 Invalid Sytnax or Database name is null

ORA-17112 Invalid thread interval specified

ORA-17161 Invalid transaction mode used

Appendix D

General JDBC Messages

D-9

Table D-2 (Cont.) JDBC Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17002 Io exception

ORA-17092 JDBC statements cannot be created or executed at end of call

processing

ORA-17134 Length of named parameter in SQL exceeded 32 characters

ORA-17136 Malformed DATALINK URL, try getString() instead

ORA-17033 Malformed SQL92 string at position

ORA-17148 Method only implemented in thin

ORA-17159 metric value for end-to-end tracing is too long

ORA-17021 Missing defines

ORA-17022 Missing defines at index

ORA-17061 Missing descriptor

ORA-17041 Missing IN or OUT parameter at index:

ORA-17082 No current row

ORA-17024 No data read

ORA-17108 No max length specified in defineColumnType

ORA-17050 no such element in vector

ORA-17056 Non supported character set (add orai18n.jar in your classpath)

ORA-17034 Non supported SQL92 token at position

ORA-17173 Not all return parameters registered

ORA-17063 Not in a transaction

ORA-17083 Not on the insert row

ORA-17026 Numeric Overflow

ORA-17094 Object type version mismatched

ORA-17093 OCI operation returned OCI_SUCCESS_WITH_INFO

ORA-17090 operation not allowed

ORA-17135 Parameter name used in setXXXStream appears more than once in

SQL

ORA-17012 Parameter Type Conflict

ORA-17167 PKI classes not found. To use 'connect /' functionality, oraclepki.jar

must be in the classpath

ORA-17030 READ_COMMITTED and SERIALIZABLE are the only valid

transaction levels

ORA-17062 Ref cursor is invalid

ORA-17014 ResultSet.next was not called

ORA-17031 setAutoClose: Only support auto close mode on

ORA-17029 setReadOnly: Read-only connections not supported

ORA-17157 setString can only process strings of less than 32766 chararacters

ORA-17104 SQL statement to execute cannot be empty or null

ORA-17129 SQL string is not a DML Statement

Appendix D

General JDBC Messages

D-10

Table D-2 (Cont.) JDBC Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17128 SQL string is not Query

ORA-17263 SQLXML cannot create a Result of that type

ORA_17264 SQLXML cannoct create a Source of that type

ORA-17259 SQLXML cannot find the XML support jar file in the classpath

ORA-17109 standard Java character encoding not found

ORA-17095 Statement cache size has not been set

ORA-17096 Statement Caching cannot be enabled for this logical connection.

ORA-17144 statement handle not executed

ORA-17016 Statement timed out

ORA-17015 Statement was cancelled

ORA-17027 Stream has already been closed

ORA-17040 Sub Protocol must be specified in connection URL

ORA-17172 That value of the attribute cannot exceed 400 chars

ORA-17171 The attribute length cannot exceed 30 chars

ORA-17054 The LOB locator is not valid

ORA-17170 The Namespace cannot be empty

ORA-17174 The only supported namespace is CLIENTCONTEXT

ORA-17053 The size is not valid

ORA-17051 This API cannot be be used for non-UDT types

ORA-17149 This is already a proxy session

ORA-17152 This method is only implemented in logical connections

ORA-17153 This method is only implemented in physical connections

ORA-17052 This ref is not valid

ORA-17113 Thread interval value is more than the cache timeout value

ORA-17091 Unable to create resultset at the requested type and/or concurrency

level

ORA-17086 Undefined column value on the insert row

ORA-17048 Undefined type

ORA-17005 Unsupported column type

ORA-17023 Unsupported feature

ORA-17162 Unsupported holdability value

ORA-17088 Unsupported syntax for requested resultset type and concurrency

level

ORA-17133 UNUSED

ORA-17069 Use explicit XA call

ORA-17079 User credentials doesn't match the existing ones

ORA-17085 Value conflicts occurs

ORA-17150 Wrong arguments for proxy session

Appendix D

General JDBC Messages

D-11

D.3 Native XA Messages

The following sections cover the JDBC error messages that are specific to the Native

XA feature:

• Native XA Messages Sorted by ORA Number

• Native XA Messages Sorted in Alphabetic Order

D.3.1 Native XA Messages Sorted by ORA Number

The following table lists the Native XA messages sorted by the

ORA

number:

Table D-3 Native XA Messages Sorted by ORA Number

ORA Number Message

ORA-17200 Unable to properly convert XA open string from Java to C

ORA-17201 Unable to properly convert XA close string from Java to C

ORA-17202 Unable to properly convert RM name from Java to C

ORA-17203 Could not casting pointer type to jlong

ORA-17204 Input array too short to hold OCI handles

ORA-17205 Failed to obtain OCISvcCtx handle from C-XA using xaoSvcCtx

ORA-17206 Failed to obtain OCIEnv handle from C-XA using xaoEnv

ORA-17207 The tnsEntry property was not set in DataSource

ORA-17213 C-XA returned XAER_RMERR during xa_open

ORA-17215 C-XA returned XAER_INVAL during xa_open

ORA-17216 C-XA returned XAER_PROTO during xa_open

ORA-17233 C-XA returned XAER_RMERR during xa_close

ORA-17235 C-XA returned XAER_INVAL during xa_close

ORA-17236 C-XA returned XAER_PROTO during xa_close

D.3.2 Native XA Messages Sorted in Alphabetic Order

The following table lists the Native XA messages sorted in the alphabetic order:

Table D-4 Native XA Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17203 Could not casting pointer type to jlong

ORA-17235 C-XA returned XAER_INVAL during xa_close

ORA-17215 C-XA returned XAER_INVAL during xa_open

ORA-17236 C-XA returned XAER_PROTO during xa_close

ORA-17216 C-XA returned XAER_PROTO during xa_open

ORA-17233 C-XA returned XAER_RMERR during xa_close

ORA-17213 C-XA returned XAER_RMERR during xa_open

Appendix D

Native XA Messages

D-12

Table D-4 (Cont.) Native XA Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17206 Failed to obtain OCIEnv handle from C-XA using xaoEnv

ORA-17205 Failed to obtain OCISvcCtx handle from C-XA using xaoSvcCtx

ORA-17204 Input array too short to hold OCI handles

ORA-17207 The tnsEntry property was not set in DataSource

ORA-17202 Unable to properly convert RM name from Java to C

ORA-17201 Unable to properly convert XA close string from Java to C

ORA-17200 Unable to properly convert XA open string from Java to C

D.4 TTC Messages

This section lists TTC error messages, first sorted by the

ORA

number and then in alphabetic

order in the following subsections:

• TTC Messages Sorted by ORA Number

• TTC Messages Sorted in Alphabetic Order

D.4.1 TTC Messages Sorted by ORA Number

The following table lists the TTC messages sorted by the

ORA

number:

Table D-5 TTC Messages Sorted by ORA Number

ORA Number Message

ORA-17401 Protocol violation

ORA-17402 Only one RPA message is expected

ORA-17403 Only one RXH message is expected

ORA-17404 Received more RXDs than expected

ORA-17405 UAC length is not zero

ORA-17406 Exceeding maximum buffer length

ORA-17407 invalid Type Representation(setRep)

ORA-17408 invalid Type Representation(getRep)

ORA-17409 invalid buffer length

ORA-17410 No more data to read from socket

ORA-17411 Data Type representations mismatch

ORA-17412 Bigger type length than Maximum

ORA-17413 Exceding key size

ORA-17414 Insufficient Buffer size to store Columns Names

ORA-17415 This type hasn't been handled

ORA-17416 FATAL

ORA-17417 NLS Problem, failed to decode column names

Appendix D

TTC Messages

D-13

Table D-5 (Cont.) TTC Messages Sorted by ORA Number

ORA Number Message

ORA-17418 Internal structure's field length error

ORA-17419 Invalid number of columns returned

ORA-17420 Oracle Version not defined

ORA-17421 Types or Connection not defined

ORA-17422 Invalid class in factory

ORA-17423 Using a PLSQL block without an IOV defined

ORA-17424 Attempting different marshaling operation

ORA-17425 Returning a stream in PLSQL block

ORA-17426 Both IN and OUT binds are NULL

ORA-17427 Using Uninitialized OAC

ORA-17428 Logon must be called after connect

ORA-17429 Must be at least connected to server

ORA-17430 Must be logged on to server

ORA-17431 SQL Statement to parse is null

ORA-17432 invalid options in all7

ORA-17433 invalid arguments in call

ORA-17434 not in streaming mode

ORA-17435 invalid number of in_out_binds in IOV

ORA-17436 invalid number of outbinds

ORA-17437 Error in PLSQL block IN/OUT argument(s)

ORA-17438 Internal - Unexpected value

ORA-17439 Invalid SQL type

ORA-17440 DBItem/DBType is null

ORA-17441 Oracle Version not supported. Minimum supported version is 7.2.3.

ORA-17442 Refcursor value is invalid

ORA-17443 Null user or password not supported in THIN driver

ORA-17444 TTC Protocol version received from server not supported

ORA-17445 LOB already opened in the same transaction

ORA-17446 LOB already closed in the same transaction

ORA-17447 OALL8 is in an inconsistent state

D.4.2 TTC Messages Sorted in Alphabetic Order

The following table lists the TTC messages in the alphabetic order:

Table D-6 TTC Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17424 Attempting different marshaling operation

Appendix D

TTC Messages

D-14

Table D-6 (Cont.) TTC Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17412 Bigger type length than Maximum

ORA-17426 Both IN and OUT binds are NULL

ORA-17411 Data Type representations mismatch

ORA-17440 DBItem/DBType is null

ORA-17437 Error in PLSQL block IN/OUT argument(s)

ORA-17413 Exceding key size

ORA-17406 Exceeding maximum buffer length

ORA-17416 FATAL

ORA-17414 Insufficient Buffer size to store Columns Names

ORA-17438 Internal - Unexpected value

ORA-17418 Internal structure's field length error

ORA-17433 invalid arguments in call

ORA-17409 invalid buffer length

ORA-17422 Invalid class in factory

ORA-17419 Invalid number of columns returned

ORA-17435 invalid number of in_out_binds in IOV

ORA-17436 invalid number of outbinds

ORA-17432 invalid options in all7

ORA-17439 Invalid SQL type

ORA-17408 invalid Type Representation(getRep)

ORA-17407 invalid Type Representation(setRep)

ORA-17446 LOB already closed in the same transaction

ORA-17445 LOB already opened in the same transaction

ORA-17428 Logon must be called after connect

ORA-17429 Must be at least connected to server

ORA-17430 Must be logged on to server

ORA-17417 NLS Problem, failed to decode column names

ORA-17410 No more data to read from socket

ORA-17434 not in streaming mode

ORA-17443 Null user or password not supported in THIN driver

ORA-17447 OALL8 is in an inconsistent state

ORA-17402 Only one RPA message is expected

ORA-17403 Only one RXH message is expected

ORA-17420 Oracle Version not defined

ORA-17441 Oracle Version not supported. Minimum supported version is

7.2.3.

ORA-17401 Protocol violation

ORA-17404 Received more RXDs than expected

Appendix D

TTC Messages

D-15

Table D-6 (Cont.) TTC Messages Sorted in Alphabetic Order

ORA Number Message

ORA-17442 Refcursor value is invalid

ORA-17425 Returning a stream in PLSQL block

ORA-17431 SQL Statement to parse is null

ORA-17415 This type hasn't been handled

ORA-17444 TTC Protocol version received from server not supported

ORA-17421 Types or Connection not defined

ORA-17405 UAC length is not zero

ORA-17423 Using a PLSQL block without an IOV defined

ORA-17427 Using Uninitialized OAC

Appendix D

TTC Messages

D-16

Troubleshooting

This appendix describes how to troubleshoot a Java Database Connectivity (JDBC)

application in the following topics:

• Common Problems

• Basic Debugging Procedures

E.1 Common Problems

This section describes some common problems that you might encounter while using Oracle

JDBC drivers. These problems include:

• Memory Consumption for CHAR Columns Defined as OUT or IN/OUT Variables

• Memory Leaks and Running Out of Cursors

• Opening More than 16 OCI Connections for a Process

• Using statement.cancel

• Using JDBC with Firewalls

• Frequent Abrupt Disconnection from Server

• Network Adapter Cannot Establish Connection

E.1.1 Memory Consumption for CHAR Columns Defined as OUT or

IN/OUT Variables

In PL/SQL, when a

CHAR

or a

VARCHAR2

column is defined as a

OUT

IN/OUT

variable, the

driver allocates a

CHAR

array of 32512 chars. This can cause a memory consumption

problem. JDBC Thin driver does not allocate memory when using

VARCHAR2

output type. But

JDBC OCI driver allocates memory for both

CHAR

and

VARCHAR2

types. So, CPU load in OCI

driver is higher than Thin driver.

At previous releases, the solution to the problem was to invoke the

Statement.setMaxFieldSize

method. A better solution is to use

OracleCallableStatement.registerOutParameter

. Oracle encourages you always to call

registerOutParameter (int paramIndex, int sqlType, int scale, int maxLength)

each

CHAR

VARCHAR2

column. This method is defined in

oracle.jdbc.OracleCallableStatement

. Use the fourth argument,

maxLength

, to limit the

memory consumption. This parameter tells the driver how many characters are necessary to

store this column. The column is truncated if the character array cannot hold the column data.

The third argument,

scale

, is ignored by the driver.

E.1.2 Memory Leaks and Running Out of Cursors

If you receive messages that you are running out of cursors or that you are running out of

memory, make sure that all your

Statement

and

ResultSet

objects are explicitly closed.

E-1

Oracle JDBC drivers do not have finalizer methods. They perform cleanup routines by

using the

method of the

ResultSet

and

Statement

classes. If you do not

explicitly close your result set and statement objects, significant memory leaks can

occur. You could also run out of cursors in the database. Closing a statement releases

the corresponding cursor in the database.

Similarly, you must explicitly close

Connection

objects to avoid leaking and running out

of cursors on the server-side. When you close the connection, the JDBC driver closes

any open statement objects associated with it, thus releasing the cursor on the server-

side.

E.1.3 Opening More than 16 OCI Connections for a Process

You may find that you are unable to open more than approximately 16 JDBC-OCI

connections for a process at any given time. The most likely reasons for this would be

either that the number of processes on the server exceeded the limit specified in the

initialization file, or that the per-process file descriptors limit was exceeded. It is

important to note that one JDBC-OCI connection can use more than one file descriptor

(it might use anywhere between 3 and 4 file descriptors).

If the server allows more than 16 processes, then the problem could be with the per-

process file descriptor limit. The possible solution would be to increase this limit.

E.1.4 Using statement.cancel

The JDBC standard method

Statement.cancel

attempts to cleanly stop the execution

of a SQL statement by sending a message to the database. In response, the database

stops execution and replies with an error message. The Java thread that invoked

Statement.execute

waits on the server, and continues execution only when it receives

the error reply message invoked by the call of the other thread to

Statement.cancel

method.

As a result, the

Statement.cancel

method relies on the correct functioning of the

network and the database. If either the network connection is broken or the database

server is hung, the client does not receive the error reply to the cancel message.

Frequently, when the server process dies, JDBC receives an

IOException

that frees

the thread that invoked

Statement.execute

. In some circumstances, the server is

hung, but JDBC does not receive an

IOException

. The

Statement.cancel

method

does not free the thread that initiated the

Statement.execute

method.

Appendix E

Common Problems

E-2

Note:

Remember the following points while working with the

Statement.cancel

method:

• Distinguish between Connection-level and Statement-level cancel. If a

nonstatement execution, for example, a

ROLLBACK

is cancelled by a

statement.cancel

method, then we replay the command (only if it is

ROLLBACK

COMMIT

autoCommit ON

autoCommit OFF

VERSION

). To guarantee data integrity,

we do not replay statement executions.

• Synchronize statement execution and statement cancel, so that the execution

does not return until the cancel call is sent to the Database. This provides a

better chance for the executing statement to be cancelled.

• Synchronize cancel calls, so that any new cancel request is ignored until the

cancel in progress has completed the full protocol, that is, after the database

receives an interrupt, act on it, and notify JDBC.

When JDBC does not receive an

IOException

, Oracle Net may eventually time out and close

the connection. This causes an

IOException

and frees the thread. This process can take

many minutes. For information about how to control this time-out, see the description of the

readTimeout

property for

OracleDatasource.setConnectionProperties

. You can also tune

this time-out with certain Oracle Net settings.

The JDBC standard method

Statement.setQueryTimeout

relies on the

Statement.cancel

method. If execution continues longer than the specified time-out interval, then the monitor

thread calls the

Statement.cancel

method. This is subject to all the same limitations

described previously. As a result, there are cases when the time-out does not free the thread

that invoked the

Statement.execute

method.

The length of time between execution and cancellation is not precise. This interval is no less

than the specified time-out interval but can be several seconds longer. If the application has

active threads running at high priority, then the interval can be arbitrarily longer. The monitor

thread runs at high priority, but other high priority threads may keep it from running

indefinitely. Note that the monitor thread is started only if there are statements executed with

non zero time-out. There is only one monitor thread that monitors all Oracle JDBC statement

execution.

Note:

The

Statement.cancel

method and the

Statement.setQueryTimeout

method are

not supported in the server-side internal driver. The server-side internal driver runs

in the single-threaded server process and the Oracle JVM implements Java threads

within this single-threaded process. If the server-side internal driver is executing a

SQL statement, then no Java thread can call the

Statement.cancel

method. This

also applies to the Oracle JDBC monitor thread.

Appendix E

Common Problems

E-3

E.1.5 Using JDBC with Firewalls

Firewall timeout for idle-connections may sever a connection. This can cause JDBC

applications to hang while waiting for a connection. You can perform one or more of

the following actions to avoid connections from being severed due to firewall timeout:

• If you are using connection caching or connection pooling, then always set the

inactivity timeout value on the connection cache to be shorter than the firewall idle

timeout value.

• Pass

oracle.jdbc.ReadTimeout

as connection property to enable read timeout on

socket. The timeout value is in milliseconds.

• For both JDBC OCI and JDBC Thin drivers, use net descriptor to connect to the

database and specify the

ENABLE=BROKEN

parameter in the

DESCRIPTION

clause in

the connect descriptor. Also, set a lower value for

TCP_KEEPALIVE_INTERVAL

• Enable Oracle Net DCD by setting

SQLNET.EXPIRE_TIME=1

in the

sqlnet.ora

file

on the server-side.

E.1.6 Frequent Abrupt Disconnection from Server

If the network is not reliable, then it is difficult for a client to detect the frequent

disconnections when the server is abruptly disconnected. By default, a client running

on Linux takes 7200 seconds (2 hours) to sense the abrupt disconnections. This value

is equal to the value of the

tcp_keepalive_time

property. If you want your application

to detect the disconnections faster, then you must set the value of the

tcp_keepalive_time

tcp_keepalive_interval

, and

tcp_keepalive_probes

properties to a lower value at the operating system level.

Note:

Setting a low value for the

tcp_keepalive_interval

property leads to

frequent probe packets on the network, which can make the system slower.

So, the value of this property should be set appropriately based on the

system requirements.

Also, you must specify the

ENABLE=BROKEN

parameter in the

DESCRIPTION

clause in the

connection descriptor. For example:

jdbc:oracle:thin:@(DESCRIPTION=(ENABLE=BROKEN)(ADDRESS=(PROTOCOL=tcp)(PORT=5221)

(HOST=myhost))(CONNECT_DATA=(SERVICE_NAME=orcl)))

E.1.7 Network Adapter Cannot Establish Connection

You may receive the following error while trying to establish a connection from a JDBC

application to an Oracle instance:

java.sql.SQLException: Io exception:

The Network Adapter could not establish connection

SQLException: SQLState (null) vendor code (17002)

Appendix E

Common Problems

E-4

This error may occur even if all or any of the following conditions is true:

• You are able to establish a SQL*Plus connection from the same client to the same Oracle

instance.

• You are able to establish a JDBC OCI connection, but not a JDBC Thin connection from

the same client to the same Oracle instance.

• The same JDBC application is able to connect from a different client to the same Oracle

instance.

• The same behavior applies whether the initial JDBC connection string specifies a host

name or an IP address.

One or more of the following reasons can cause this error:

• The host name to which you are trying to establish the connection is incorrect.

• The port number you are using to establish the connection is wrong.

• The NIC card supports both IPv4 and IPv6.

• The Oracle instance is configured for MTS, but the JDBC connection uses a shared

server instead of a dedicated server.

You can quickly diagnose these above-mentioned reasons by using SQL*Plus, except for the

issue with the NIC card. The following sections specify how to resolve this error, and also

contains a sample application:

• Oracle Instance Configured with MTS Server Uses Shared Server

• JDBC Thin Driver with NIC Card Supporting Both IPv4 and IPv6

• Sample Application

E.1.7.1 Oracle Instance Configured with MTS Server Uses Shared Server

For resolving this error, you must verify whether the Oracle instance is configured for Multi-

threaded Server (MTS) or not. If the Oracle instance is not configured for MTS, then it must

be configured.

If the Oracle instance is configured for MTS, then you must force the JDBC connection to use

a dedicated server instead of a shared server. You can achieve this by reconfiguring the

server to use dedicated connections only. If it is not feasible to configure your server to use

only dedicated connections, then you perform the following steps to set it from the client side:

For JDBC OCI Client

1. Add the

(SERVER=DEDICATED)

property to the TNS connection string stored in the

tnsnames.ora

file on the client.

2. Set the

USER_DEDICATED_SERVER=ON

in the

sqlnet.ora

file on the client.

For JDBC Thin:

You must specify a full name-value pair connection string (the same as it may appear in the

tnsnames.ora

file) instead of the short JDBC Thin syntax. For example, instead of the

jdbc:oracle:thin:@host:port:sid

" connection string, you must use a connection string of

the following form:

"jdbc:oracle:thin:@(DESCRIPTION=" +

"(ADDRESS_LIST=" +

"(ADDRESS=(PROTOCOL=TCP)" +

Appendix E

Common Problems

E-5

"(HOST=host)" +

"(PORT=port)" +

")" +

"(CONNECT_DATA=" +

"(SERVICE_NAME=sid)" +

"(SERVER=DEDICATED)" +

")" +

")"

E.1.7.2 JDBC Thin Driver with NIC Card Supporting Both IPv4 and IPv6

If the Network Interface Controller (NIC) card of the server is configured to support

both IPv4 and IPv6, then some services may start with IPv6. Any client application that

tries to connect using IPv4 to the service that is running with IPv6 (or the other way

round) receives a connection refused error. If a JDBC thin client application tries to

connect to the Database server, then the application may stop responding or fail with

the following error:

java.sql.SQLException: Io exception: The Network Adapter could not establish the

connection Error Code: 17002

Use any of the following solutions to resolve this error:

• Indicate the Java Virtual Machine (JVM) to use IP protocol version 4. Launch the

JVM, where the JDBC application is running, with the

Djava.net.preferIPv4Stack

parameter as

true

. For example, suppose you are

running a JDBC application named

jdbcTest

. Then execute the application in the

following way:

java -Djava.net.preferIPv4Stack=true jdbcTest

• Use the OCI JDBC driver.

E.1.7.3 Sample Application

Example E-1 shows a basic JDBC program that connects to a Database and can be

used to test your connection. It enables to try all forms of connection using Oracle

JDBC drivers.

Example E-1 Basic JDBC Program to Connect to a Database in Five Different

Ways

import java.sql.*;

public class Jdbctest

{

public static void main (String args[])

{

try

{

/* Uncomment the next line for more connection information */

// DriverManager.setLogStream(System.out);

/* Set the host, port, and sid below to match the entries in

the listener.ora */

String host = "myhost.oracle.com";

String port = "5221";

String sid = "orcl";

// or pass on command line arguments for all three

items

if ( args.length >= 3 )

Appendix E

Common Problems

E-6

{

host = args[0];

port = args[1];

sid = args[2];

}

String s1 = "jdbc:oracle:thin:@" + host + ":" + port + ":" + sid ;

if ( args.length == 1 )

{

s1 = "jdbc:oracle:oci8:@" + args[0];

}

if ( args.length == 4 )

{

s1 = "jdbc:oracle:" + args[3] + ":@" +

"(description=(address=(host=" + host+ ")

(protocol=tcp)(port=" + port+ "))(connect_data=(sid="+ sid + ")))";

}

System.out.println( "Connecting with: " );

System.out.println( s1 );

DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());

Connection conn =

DriverManager.getConnection( s1,"hr","hr");

DatabaseMetaData dmd = conn.getMetaData();

System.out.println("DriverVersion:["+dmd.getDriverVersion()+"]");

System.out.println("DriverMajorVersion:

["+dmd.getDriverMajorVersion()+"]");

System.out.println("DriverMinorVersion:

["+dmd.getDriverMinorVersion()+"]");

System.out.println("DriverName:["+dmd.getDriverName()+"]");

if ( conn!=null )

conn.close();

System.out.println("Done.");

}

catch ( SQLException e )

{

System.out.println ("\n*** Java Stack Trace ***\n");

e.printStackTrace();

System.out.println ("\n*** SQLException caught ***\n");

while ( e != null )

{

System.out.println ("SQLState: " + e.getSQLState

());

System.out.println ("Message: " + e.getMessage

());

System.out.println ("Error Code: " + e.getErrorCode

());

e = e.getNextException ();

System.out.println ("");

}

E.2 Basic Debugging Procedures

This section describes strategies for debugging a JDBC program:

• Oracle Net Tracing to Trap Network Events

• Third Party Debugging Tools

Appendix E

Basic Debugging Procedures

E-7

Related Topics

• About Processing SQL Exceptions

E.2.1 Oracle Net Tracing to Trap Network Events

You can enable client and server Oracle-Net trace to trap the packets sent over Oracle

Net. You can use client-side tracing only for the JDBC OCI driver; it is not supported

for the JDBC Thin driver.

The trace facility produces a detailed sequence of statements that describe network

events as they execute. "Tracing" an operation lets you obtain more information about

the internal operations of the event. This information is printed to a readable file that

identifies the events that led to the error. Several Oracle Net parameters in the

SQLNET.ORA

file control the gathering of trace information. After setting the parameters

SQLNET.ORA

, you must make a new connection for tracing to be performed.

The higher the trace level, the more detail is captured in the trace file. Because the

trace file can be hard to understand, start with a trace level of 4 when enabling tracing.

The first part of the trace file contains connection handshake information, so look

beyond this for the SQL statements and error messages related to your JDBC

program.

Note:

The trace facility uses a large amount of disk space and might have

significant impact upon system performance. Therefore, enable tracing only

when necessary.

Related Topics

• Oracle Call Interface Programmer's Guide

E.2.1.1 Client-Side Tracing

Set the following parameters in the

SQLNET.ORA

file on the client system.

Note:

Starting from Oracle Database 12c Release 1 (12.1), Oracle recommends

you to use the configuration parameters present in the new XML

configuration file

oraaccess.xml

instead of the OCI-specific configuration

parameters present in the

sqlnet.ora

file. However, the configuration

parameters present in the

sqlnet.ora

file are still supported.

E.2.1.1.1 TRACE_LEVEL_CLIENT

Purpose:

Turns tracing

off

to a certain specified level.

Appendix E

Basic Debugging Procedures

E-8

Default Value:

0 or OFF

Available Values:

• 0 or

OFF

- No trace output

• 4 or

USER

- User trace information

• 10 or

ADMIN

- Administration trace information

• 16 or

SUPPORT

- WorldWide Customer Support trace information

Example:

TRACE_LEVEL_CLIENT=10

E.2.1.1.2 TRACE_DIRECTORY_CLIENT

Purpose:

Specifies the destination directory of the trace file.

Default Value:

ORACLE_HOME/network/trace

Example:

UNIX:

TRACE_DIRECTORY_CLIENT=/oracle/traces

Windows:

TRACE_DIRECTORY_CLIENT=C:\ORACLE\TRACES

E.2.1.1.3 TRACE_FILE_CLIENT

Purpose:

Specifies the name of the client trace file.

Default Value:

SQLNET.TRC

Example:

TRACE_FILE_CLIENT=cli_Connection1.trc

Note:

Ensure that the name you choose for the

TRACE_FILE_CLIENT

file is different from

the name you choose for the

TRACE_FILE_SERVER

file.

E.2.1.1.4 TRACE_UNIQUE_CLIENT

Purpose:

Gives each client-side trace a unique name to prevent each trace file from being overwritten

with the next occurrence of a client trace. The

PID

is attached to the end of the file name.

Appendix E

Basic Debugging Procedures

E-9

Default Value:

OFF

Example:

TRACE_UNIQUE_CLIENT = ON

E.2.1.2 Server-Side Tracing

Set the following parameters in the

SQLNET.ORA

file on the server system. Each

connection will generate a separate file with a unique file name.

Note:

Starting from Oracle Database 12c Release 1 (12.1), Oracle recommends

you to use the configuration parameters present in the new XML

configuration file

oraaccess.xml

instead of the OCI-specific configuration

parameters present in the

sqlnet.ora

file. However, the configuration

parameters present in the

sqlnet.ora

file are still supported.

E.2.1.2.1 TRACE_LEVEL_SERVER

Purpose:

Turns tracing

off

to a certain specified level.

Default Value:

0 or

OFF

Available Values:

• 0 or

OFF

- No trace output

• 4 or

USER

- User trace information

• 10 or

ADMIN

- Administration trace information

• 16 or

SUPPORT

- WorldWide Customer Support trace information

Example:

TRACE_LEVEL_SERVER=10

E.2.1.2.2 TRACE_DIRECTORY_SERVER

Purpose:

Specifies the destination directory of the trace file.

Default Value:

ORACLE_HOME/network/trace

Example:

TRACE_DIRECTORY_SERVER=/oracle/traces

Appendix E

Basic Debugging Procedures

E-10

E.2.1.2.3 TRACE_FILE_SERVER

Purpose:

Specifies the name of the server trace file.

Default Value:

SERVER.TRC

Example:

TRACE_FILE_SERVER= svr_Connection1.trc

Note:

Ensure that the name you choose for the

TRACE_FILE_SERVER

file is different from

the name you choose for the

TRACE_FILE_CLIENT

file.

E.2.2 Third Party Debugging Tools

You can use tools such as JDBCSpy and JDBCTest from Intersolv to troubleshoot at the

JDBC API level. These tools are similar to ODBC Spy and ODBC Test tools.

Appendix E

Basic Debugging Procedures

E-11

Index

AC, 30-1

Accessing PL/SQL Associative Arrays, 4-5

ANYDATA, 4-21

ANYTYPE, 4-21

application continuity, 30-1

configuring Oracle database, 30-6

delaying the reconnection, 30-16

disabling replay, 30-21

identifying request boundaries, 30-9

registering a connection callback, 30-11

retaining mutable values, 30-18

ARRAY

objects, creating, 16-7

arrays

defined, 16-1

getting, 16-11

named, 16-1

passing to callable statement, 16-13

retrieving from a result set, 16-8

retrieving partial arrays, 16-10

using type maps, 16-14

working with, 16-1

authentication (security), 9-9

auto-commit, 2-13

auto-commit mode

disabling, C-2

result set behavior, C-2

batch jobs, authenticating users in, 9-31

batch updates--see update batching, 21-1

BFILE

class, 4-7

defined, 12-8

BFILE locator, selecting, 4-8

BLOB

class, 4-7

locators

selecting, 4-8

branch qualifier (distributed transactions), 34-13

CachedRowSet, 18-6

caching, client-side

Oracle use for scrollable result sets, 17-1

callable statement

using getOracleObject() method, 11-8

cancelling

SQL statements, E-2

casting return values, 11-11

catalog arguments (DatabaseMetaData), A-16

CHAR columns

using setFixedCHAR() to match in WHERE,

11-15

character sets, 4-16

CLOB

class, 4-7

locators, selecting, 4-8

close method, 20-12

close() method, E-1

collections

defined, 16-1

collections (nested tables and arrays), 16-6

column types

defining, 21-11

redefining, 21-9

commit a distributed transaction branch, 34-8

commit changes to database, 2-13

connection

closing, 2-15

opening, 2-9

connection properties, 8-7

put() method, 8-9

connections

read-only, C-6

constants for SQL types, 4-28

CursorName

limitations, A-15

cursors, E-1

custom collection classes

defined, 16-2

custom Java classes, 4-3

defined, 13-1

custom object classes

creating, 13-6

Index-1

custom object classes (continued)

defined, 13-1

custom reference classes

defined, 15-1

data conversions, 11-4

LONG, 12-3

LONG RAW, 12-3

data sources

creating and connecting (with JNDI), 8-5

creating and connecting (without JNDI), 8-5

Oracle implementation, 8-2

properties, 8-2

standard interface, 8-2

data streaming

avoiding, 12-6

data type mappings, 11-1

data types

Java, 11-1

Java native, 11-1

JDBC, 11-1

Oracle SQL, 11-1

database

connecting

with server-side internal driver, 7-1

connection testing, 2-6

Database Resident Connection Pooling

DRCP, 25-1

database specifiers, 8-11

database URL

including userid and password, 2-9

database URL, specifying, 2-9

database URLs

and database specifiers, 8-11

DatabaseMetaData calls, A-16

datasources, 8-1

and JNDI, 8-5

DATE class, 4-8

debugging JDBC programs, E-7

defaultConnection() method, 7-1

distributed transaction ID component, 34-13

distributed transactions

branch qualifier, 34-13

check for same resource manager, 34-8

commit a transaction branch, 34-8

components and scenarios, 34-2

concepts, 34-2

distributed transaction ID component, 34-13

end a transaction branch, 34-8

example of implementation, 34-16

forget, 34-8

global transaction identifier, 34-13

ID format identifier, 34-13

distributed transactions (continued)

obtain the list of transaction brances during

recovery, 34-8

Oracle XA connection implementation, 34-7

Oracle XA data source implementation, 34-6

Oracle XA ID implementation, 34-13

Oracle XA optimizations, 34-16

Oracle XA resource implementation, 34-8

overview, 34-1

prepare a transaction branch, 34-8

roll back a transaction branch, 34-8

start a transaction branch, 34-8

transaction branch ID component, 34-13

XA connection interface, 34-7

XA data source interface, 34-6

XA error handling, 34-16

XA exception classes, 34-14

XA ID interface, 34-13

XA resource functionality, 34-8

XA resource interface, 34-8

DML Returning, 4-4, 4-30

example, 4-31

limitations, 4-32

Oracle-specific APIs, 4-30

running statements, 4-31

Double.NaN

restrictions on use, 4-8

end a distributed transaction branch, 34-8

Enterprise Java Beans (EJB), 18-8

environment variables

specifying, 2-4

errors

general JDBC message structure, D-1

general JDBC messages, listed, D-1

processing exceptions, 2-28

TTC messages, listed, D-13

explicit Statement caching

definition of, 20-3

extensions to JDBC, Oracle, 4-1, 11-1, 13-1,

15-1, 16-1, 21-1

external changes (result set)

defined, 17-6

visibility vs. detection, 17-7

external file

defined, 12-8

fetch direction in result sets, 17-5

fetch size, result sets, 17-4

FilteredRowSet, 18-12

finalizer methods, E-1

Index

Index-2

Firewalls, using with JDBC, E-4

Float.NaN

restrictions on use, 4-8

floating-point compliance, A-16

format identifier, transaction ID, 34-13

function call syntax, JDBC escape syntax, A-14

getBinaryStream() method, 12-4

getBytes() method, 12-5

getColumns, 2-17

getConnection() method, 7-1

getCursorName() method

limitations, A-15

getLogicalTransactionId method, 29-3

getMoreResultSet(int), 2-19

getObject() method

for ORAData objects, 13-13

return types, 11-8

getOracleObject() method

return types, 11-7, 11-8

using in callable statement, 11-8

using in result set, 11-8

getStatementCacheSize() method

code example, 20-6

getXXX() methods

casting return values, 11-11

for specific data types, 11-10

global transaction identifier (distributed

transactions), 34-13

global transactions, 34-1

globalization, 19-1

using, 19-1

IEEE 754 floating-point compliance, A-16

implicit Statement caching

definition of, 20-2

Least Recently Used (LRU) algorithm, 20-3

Instant Client feature, 6-2

internal changes (result set)

defined, 17-6

isColumnInvisible, 2-16

isSameRM() (distributed transactions), 34-8

Java

compiling and running, 2-5

data types, 11-1

native data types, 11-1

stored procedures, 2-28

Java (continued)

stream data, 12-1

Java Naming and Directory Interface (JNDI), 8-1

Java Sockets, 1-3

Java Virtual Machine (JVM), 7-1

java.sql.Connection interface

close method, 20-12

java.sql.Statement interface

close method, 20-12

java.util.Properties, 24-5

JDBC

and IDEs, 1-8

basic program, 2-7

data types, 11-1

importing packages, 2-8

limitations of Oracle extensions, A-15

sample files, 2-5

testing, 2-6

JDBC drivers

choosing a driver for your needs, 1-5

common problems, E-1

introduction, 1-2

JDBC escape syntax, A-9

function call syntax, A-14

LIKE escape characters, A-13

outer joins, A-14

scalar functions, A-12

time and date literals, A-10

translating to SQL example, A-14

JdbcCheckup program, 2-6

JDBCRowSet, 18-9

JDBCSpy, E-11

JDBCTest, E-11

JDeveloper, 1-8

JNDI

and datasources, 8-5

looking up data source, 8-5

overview of Oracle support, 8-1

registering data source, 8-5

JoinRowSet, 18-14

JVM, 7-1

KPRB driver

overview, 1-4

relation to the SQL engine, 7-1

session context, 7-3

testing, 7-4

transaction context, 7-3

URL for, 7-3

Index

Index-3

Least Recently Used (LRU) algorithm, 20-3, 24-6

LIKE escape characters, JDBC escape syntax,

A-13

limitations on setBytes() and setString(), use of

streams to avoid, 12-11

LOB

defined, 12-7

LONG

data conversions, 12-3

LONG RAW

data conversions, 12-3

LRU algorithm, 20-3

memory leaks, E-1

named arrays, 16-1

defined, 16-6

nativeXA, 8-4

network events, trapping, E-8

NLS. See globalization, 19-1

NULL

testing for, 11-5

NUMBER class, 4-8

object references

accessing object values, 15-3, 15-4

described, 15-1

passing to prepared statements, 15-3

retrieving, 15-2

retrieving from callable statement, 15-3

updating object values, 15-3, 15-4

OCI driver

described, 1-3

ODBCSpy, E-11

ODBCTest, E-11

optimization, performance, C-1

Oracle Advanced Security

support by JDBC, 9-7

Oracle data types

using, 11-1

Oracle extensions, 4-1

data type support, 4-2

limitations, A-15

catalog arguments to DatabaseMetaData

calls, A-16

CursorName, A-15

Oracle extensions (continued)

limitations (continued)

IEEE 754 floating-point compliance, A-16

JDBC outer join escapes, A-15

read-only connection, C-6

SQLWarning class, A-16

object support, 4-3

result sets, 11-6

statements, 11-6

to JDBC, 4-1, 11-1, 13-1, 15-1, 16-1, 21-1

Oracle objects

and JDBC, 13-1

Java classes which support, 13-3

mapping to custom object classes, 13-6

reading data by using SQLData interface,

13-10

working with, 13-1

writing data by using SQLData interface,

13-11

Oracle SQL data types, 11-1

oracle.jdbc., Oracle JDBC extensions, 2-8

oracle.jdbc.LogicalTransactionIdEventListener

interface, 29-3

oracle.jdbc.OracleCallableStatement interface,

4-27

oracle.jdbc.OracleConnection interface, 4-25

oracle.jdbc.OraclePreparedStatement interface,

4-26

oracle.jdbc.OracleResultSet interface, 4-27

oracle.jdbc.OracleResultSetMetaData interface,

4-28

oracle.jdbc.OracleSql class, A-14

oracle.jdbc.OracleStatement interface, 4-26

oracle.jdbc.OracleTypes class, 4-28

oracle.jdbc.xa package and subpackages, 34-5

oracle.sql.ARRAY class

methods for Java primitive types, 16-5

oracle.sql.BFILE class, 4-7

oracle.sql.BLOB class, 4-7

oracle.sql.CLOB class, 4-7

oracle.sql.data types

support, 4-6

oracle.sql.DATE class, 4-8

oracle.sql.NUMBER class, 4-8

oracle.sql.RAW class, 4-8

OracleCallableStatement interface, 4-27

OracleCallableStatement object, 20-2, 20-3

OracleConnection class, 4-25

OracleData interface

advantages, 13-6

OracleDataSource class, 8-2

OraclePreparedStatement interface, 4-26

OraclePreparedStatement object, 20-2, 20-3

OracleResultSet interface, 4-27

OracleResultSetMetaData interface, 4-28

Index

Index-4

OracleStatement interface, 4-26

OracleTypes class, 4-28

OracleXAConnection class, 34-7

OracleXADataSource class, 34-6

OracleXAResource class, 34-8

OracleXid class, 34-13

ORAData interface

additional uses, 13-16

reading data, 13-14

writing data, 13-15

orai18n.jar file, 19-2

outer joins, JDBC escape syntax, A-14

password, specifying, 2-9

PDA, 18-8

performance extensions

defining column types, 21-11

performance optimization, C-1

Personal Digital Assistant (PDA), 18-8

PL/SQL

stored procedures, 2-27

PL/SQL Associative Arrays, 4-33

prefetching rows, 21-9

suggested default, 21-10

prepare a distributed transaction branch, 34-8

put() method

for Properties object, 8-9

RAW class, 4-8

recover (distributed transactions), 34-8

REF CURSORs, 4-18

refetching rows into a result set, 17-5

registerConnectionInitializationCallback, 30-13

Remote Method Invocation (RMI), 18-8

resource managers, 34-2

result set

auto-commit mode, C-2

metadata, 4-28

Oracle extensions, 11-6

using getOracleObject() method, 11-8

result set enhancements

downgrade rules, 17-2

fetch size, 17-4

limitations, 17-2

Oracle scrollability requirements, 17-1

Oracle updatability requirements, 17-1

refetching rows, 17-5

summary of visibility of changes, 17-7

visibility vs. detection of external changes,

17-7

result set fetch size, 17-4

result set object

closing, 2-11

result set, processing, 2-10

return types

for getXXX() methods, 11-11

getObject() method, 11-8

getOracleObject() method, 11-8

return values

casting, 11-11

RMI, 18-8

roll back a distributed transaction branch, 34-8

roll back changes to database, 2-13

row prefetching

and data streams, 12-11

ROWID class

defined, 4-17

ROWID, use for result set updates, 17-1

RowSet

events and event listeners, 18-3

overview, 18-1

properties, 18-2

traversing, 18-4

scalar functions, JDBC escape syntax, A-12

SCAN

backward compatibility, 33-3

configuring the database, 33-1

connection load balancing, 33-2

maximum availability architecture

environment, 33-5

Oracle connection manager, 33-5

overview, 33-1

version, 33-3

Schema Naming, 4-4

scripts, authenticating users in, 9-31

scroll-sensitive result sets

limitations, 17-2

scrollable result sets

fetch direction, 17-5

implementation of scroll-sensitivity, 17-8

refetching rows, 17-5

visibility vs. detection of external changes,

17-7

security

authentication, 9-9

Oracle Advanced Security support, 9-7

server-side internal driver

connection to database, 7-1

server-side Thin driver, overview, 1-3

session context

for KPRB driver, 7-3

setBytes() limitations, using streams to avoid,

12-11

Index

Index-5

setCursorName() method, A-15

setDisableStmtCaching() method, 20-7

setEscapeProcessing() method, A-10

setFixedCHAR() method, 11-15

setNull(), 11-6

setObejct() method, 11-12

setObject() method

for STRUCT objects, 13-4

setOracleObject() method, 11-12

setString() limitations, using streams to avoid,

12-11

setXXX() methods, for specific data types, 11-12

Solaris

shared libraries, 34-22

specifiers

database, 8-11

SQL

data converting to Java data types, 11-4

types, constants for, 4-28

SQL engine

relation to the KPRB driver, 7-1

SQL syntax (Oracle), A-10

SQLData interface

advantages, 13-6

reading data from Oracle objects, 13-10

writing data from Oracle objects, 13-11

SQLWarning class, limitations, A-16

start a distributed transaction branch, 34-8

Statement caching

explicit

definition of, 20-3

implicit

definition of, 20-2

Least Recently Used (LRU) algorithm,

20-3

Statement object

closing, 2-11

statement.cancel(), E-2

statements

Oracle extensions, 11-6

stopping

statement execution, E-2

stored procedures

Java, 2-28

PL/SQL, 2-27

stream data, 12-1

CHAR columns, 12-7

closing, 12-10

example, 12-4

external files, 12-7

LOBs, 12-7

LONG columns, 12-2

LONG RAW columns, 12-2

multiple columns, 12-8

precautions, 12-10

stream data (continued)

RAW columns, 12-7

row prefetching, 12-11

use to avoid setBytes() and setString()

limitations, 12-11

VARCHAR columns, 12-7

stream data column

bypassing, 12-9

STRUCT object

retrieving, 13-3

retrieving attributes as oracle.sql types, 13-3

SYS.ANYDATA, 4-21

SYS.ANYTYPE, 4-21

TAF, definition of, 32-1

TCP/IP protocol, 8-13

testing

for NULL values, 11-5

Thin driver

overview, 1-3

server-side, overview, 1-3

time and date literals, JDBC escape syntax, A-10

trace facility, E-8

trace parameters

client-side, E-8

server-side, E-10

transaction branch, 34-1

transaction branch ID component, 34-13

transaction context

for KPRB driver, 7-3

transaction IDs (distributed transactions), 34-3

transaction managers, 34-2

transactions

switching between local and global, 34-4

Transparent Application Failover (TAF), definition

of, 32-1

TTC error messages, listed, D-13

type map, 11-7

adding entries, 13-8

and STRUCTs, 13-9

creating a new map, 13-9

used with arrays, 16-10

using with arrays, 16-14

type map (SQL to Java), 13-6

type maps

relationship to database connection, 7-3

unicode data, 4-13

unregisterConnectionInitializationCallback

method, 30-13

Index

Index-6

updatable result sets

limitations, 17-2

refetching rows, 17-5

update conflicts, 17-4

update batching (standard model)

adding to batch, 21-2

clearing the batch, 21-5

committing changes, 21-4

error handling, 21-7

example, 21-5

executing the batch, 21-3

intermixing batched and non-batched, 21-7

overview, 21-2

update counts, 21-5

update counts upon error, 21-7

update conflicts in result sets, 17-4

update counts

standard update batching, 21-5

upon error (standard batching), 21-7

URLs

for KPRB driver, 7-3

userid, specifying, 2-9

WebRowSet, 18-10

window, scroll-sensitive result sets, 17-8

connection implementation, 34-7

connections (definition), 34-3

data source implementation, 34-6

data sources (definition), 34-2

definition, 34-2

error handling, 34-16

example of implementation, 34-16

exception classes, 34-14

Oracle optimizations, 34-16

Oracle transaction ID implementation, 34-13

resource implementation, 34-8

resources (definition), 34-3

transaction ID interface, 34-13

Index

Index-7