OracleAS TopLink - HowTo acquire Server Session

Date: 14/Apr/2004

Table of Contents

Introduction 

Oracle Application Server TopLink is an advanced object-to-relational persistence. It helps to build high performance applications that store persistent data in a relational database. A session represents the connection between an application and the relational database that stores its persistent objects. TopLink provides several different session objects that all implement the same Session interface. In this document we will try to understand using ServerSession.

Prerequisites 

• You must have basic knowledge of Toplink.

Software Requirements 

• Oracle9i Database installed with HR Schema
• OracleAS TopLink 10g

HowTo acquire ServerSession using OracleAS TopLink 

The session supports a shared session that can be used by multiple users or clients in a three-tiered application. It brokers client sessions to allow read and write access through a unified object cache. The server session provides a shared read only database connection that is used by all of its client for reads. All changes to objects and the database must be done through a unit of work acquired from the client session, this allows the changes to occur in a transactional object space and under an exclusive database connection.

By default, SessionManager attempts to create a new session using the specifications contained in a file called sessions.xml. This file can define one or more session configurations by name that the SessionManager makes available at runtime. This file, which must be on the root of the class path, contains all of the configuration information for the named session. This allows developers to update the configuration of a session without modifying application code. Below is a sample sessions.xml

<toplink-configuration>
   <session>
      <name>ServerSession</name>
      <project-xml>EmployeeDescriptor.xml</project-xml>
      <session-type>
         <server-session/>
      </session-type>
   </session>
</toplink-configuration>

The code snippet to retrieve a session from a session manager is shown below. Retrieving a session this way uses all defaults. If no session exists within the current instance of SessionManager, the Session Manager attempts to load a session from sessions.xml.

 

// Get the session from session.xml named 'ServerSession' ServerSession aSession = (ServerSession)SessionManager.getManager().getSession("ServerSession"); .... .... // Disconnect from the database aSession.logout();

The server session manages the client session, shared cache and connection pools. Although the server session is a TopLink session it should only be used to manage the servers client sessions. For this purpose the Server interface is provided. The Server interface does not implement the session API but only the public API required for the server session such as configuring connection pools and acquiring client sessions. Servers can create new client sessions using the acquireClientSession() method.

Steps to run the sample 

• Download the jar file from here and extract it.
• Edit <SAMPLE_HOME>/src/META-INF/EmployeeDescriptor.xml, set database parameters in the tag connection-url.
• Add toplink.jar, xmlparserv2.jar, connector.jar and classes12.jar to the classpath. Also ensure that <SAMPLE_HOME>/src/META-INF directory is added to your classpath
• From <SAMPLE_HOME>/src/oracle/otnsamples/toplink directory, Compile the java sources as shown below
  javac -d . *.java
• From <SAMPLE_HOME>/src/oracle/otnsamples/toplink directory, execute the java class as shown below
  java oracle.otnsamples.toplink.EmployeeManagement

Useful References 

• OracleAS TopLink 10g
• OracleAS TopLink Discussion Forum