O'Reilly - Java Message Service

8.3 The JMS Resource in J2EE
Java Message Service
The JNDI Environment Naming Context (ENC) is central to the J2EE platform. The JNDI
ENC specifies that JMS connection factories (Topic-ConnectionFactory and
QueueConnectionFactory) can be bound within a JNDI namespace and made available to
any J2EE component at runtime. This allows any J2EE component to become a JMS
client.
For example, the Wholesaler JMS client developed in Chapter 4, could be modeled as a
J2EE application client, which would allow it to access a JMS connection factory through
the JNDI ENC:
public class Wholesaler implements javax.jms.MessageListener{
public Wholesaler(String username, String password){
try{
}
...
InitialContext jndiEnc = new InitialContext( );
TopicConnectionFactory factory = (TopicConnectionFactory)
jndiEnc.lookup("java:comp/env/jms/broker");
connect = factory.createTopicConnection (username, password);
session =
connect.createTopicSession(false,Session.AUTO_ACKNOWLEDGE);
hotDealsTopic=(Topic)
jndiEnc.lookup("java:comp/env/jms/HotDeals");
publisher = session.createPublisher(hotDealsTopic);
...
} catch (javax.jms.JMSException jmse){
jmse.printStackTrace( ); System.exit(1);
} catch (javax.naming.NamingException jne){
jne.printStackTrace( ); System.exit(1);
}
Notice that the InitialContext did not need a set of vendor specific properties and that the
lookup( ) operations referenced a special namespace, "java:comp/env/jms/", to access the
connection factories. The JNDI ENC allows the J2EE component to remain ignorant of the
actual network location of the administered objects, and even of the vendor that
implements them. This allows the J2EE components to be portable across JMS providers
as well as J2EE platforms. In addition, the JNDI names used to locate objects are logical
bindings, so the topics or queues bound to these names can change independently of the
actual bindings used by the JMS provider.
In the XML deployment descriptor for the Wholesaler application client, the component
developer declares that a JMS connection factory and destination need to be bound within
the JNDI ENC:
Wholesaler Applicaton
Hot Deals Broker
jms/broker
javax.jms.TopicConnectionFactory
Container
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