Cache Synchronization with JMS and a Message Driven Bean (MDB)

Question

If I understand correctly, Toplink ueses the following configuration info to find the target to publish its session messages to a JMS server (having its URL as below) which provides the JNDI service that Toplink needs to look up the topic:
<cache-synchronization-manager>
<clustering-service> oracle.toplink.remote.jms.mdb.JMSPublishingOnlyClusteringService
</clustering-service>
<should-remove-connection-on-error>false</should-remove-connection-on-error>
<!-- both of the following tags are user specified and must correspond to -->
<!-- the settings that the user has made, manually, to the JMS Service -->
<jms-topic-connection-factory-name> jms/TopLinkTopicConectionFactory
</jms-topic-connection-factory-name>
<jms-topic-name>jms/TopLinkCacheSynchTopic</jms-topic-name>
<!-- both of the following tags will be required if OracleAS TopLink -->
<!-- is not running in the same JVM as the JNDI service that is hosting the JMS Topic -->
<naming-service-url>ormi://localhost:23791</naming-service-url>
<naming-service-initial-context-factory> com.evermind.server.rmi.RMIInitialContextFactory </naming-service-initial-context-factory></cache-synchronization-manager>
The MDB also uses the same JNDI service provided by the JMS server to listen to the topic which is named in the ejb-jar.xml file:
<enterprise-beans>
<message-driven>
<display-name>TopLink clustering MDB</display-name>
<ejb-name>TopLinkClusteringMDB</ejb-name>
<ejb-class>com.mycompany.mdb.ClusteringMDB</ejb-class>
<transaction-type>Container</transaction-type>
<message-driven-destination> <destination-type>javax.jms.Topic</destination-type>
</message-driven-destination>
<env-entry>
<description>TopLink session name</description>
<env-entry-name>tl_session_name_for_mdb</env-entry-name>
<env-entry-type>java.lang.String</env-entry-type>
<env-entry-value>Employee_Session</env-entry-value>
</env-entry>
<resource-ref> <description>description</description>
<res-ref-name>jms/TopLinkTopicConectionFactory</res-ref-name>
<res-type>javax.jms.TopicConnectionFactory</res-type>
<res-auth>Application</res-auth>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>
<resource-env-ref>
<resource-env-ref-name> jms/TopLinkCacheSynchTopic</resource-env-ref-name>
<resource-env-ref-type>javax.jms.Topic</resource-env-ref-type> </resource-env-ref>
</message-driven></enterprise-beans>
To do this, the EJB container that hosts the above MDB needs to be configured to know where the JMS server is by using the above URL same as in the Toplink sessions.xml file.
I am not clear that who provides the JNDI service for the Toplink session name lookup used by the MDB:
// Obtain the Session name configured in the environment variable
String sessionName = (String) myEnv.lookup(TOPLINK_SESSION_NAME);
session = SessionManager.getManager().getSession(sessionName);
so that the MDB can find the currently running Toplink session and communicate with it.
Can anybody help answer my above question and correct my understandings?
Many thanks!

Answer 1

Although TopLink is running in the application server’s VM, the only notable integration points with the server are for JTA and user-defined data sources. All of the work performed to get a session via SessionManager occurs solely within TopLink. When the call is made to retrieve a session, you aren’t getting the ‘active’ session identified by “Employee_Session” that is registered with the application server, rather a new session is created using the definition that exists for “Employee_Session” in sessions.xml.
When the call ‘session = SessionManager.getManager().getSession(“Employee_Session”)’ is made, the SessionManager simply looks for sessions.xml at the root level of its deployed jars or classpath, then looks for the “Employee_Session” tag within sessions.xml. If a session exists in the file with that name then a TopLink session object is created and returned.
Note that setting an environment entry as mentioned above simply allows for the session name to be declared dynamically. The call to ‘myEnv.lookup(“tl_session_name_for_mdb”)’ simply asks the bean’s environment for the <env-entry-value> that matches the <env-entry-name>. That string is then used in SessionManager (no different than a hard coded value would be) to identify the session in sessions.xml that is to be loaded.
I hope this makes sense.