Name
JMSDestination — Purpose: Routing
Synopsis
Message
objects are always sent to some kind of destination. In the pub/sub
model, Message objects are delivered to a topic,
identified by a Topic object. In Chapter 2, you learned that the destination of a
Message object is established when the
TopicPublisher is created:
Topic chatTopic = (Topic)jndi.lookup(topicName); TopicPublisher publisher = session.createPublisher(chatTopic); ... TextMessage message = session.createTextMessage( ); message.setText(username+" : "+text); publisher.publish(message);
The JMSDestination header identifies the
destination of a Message object using a
javax.jms.Destination object. The
Destination class is the superclass of both
Topic (pub/sub) and Queue
(p2p). The JMSDestination header is obtained using
the Message.getJMSDestination( ) method.
Identifying the destination to which a message was delivered is
valuable to JMS clients that consume messages from more than one
topic or queue. MessageListener objects might, for
example, listen to multiple consumers
(TopicSubscriber or
QueueReceiver types) so that they receive messages
from more than one topic or queue. For example, the
Chat client from Chapter 2
could be modified to subscribe to more than one chat topic at a time.
In this scenario, the onMessage( ) method of the
MessageListener would use the
JMSDestination header to identify which chat topic
a message came from:
public void onMessage(Message message){ try { TextMessage textMessage = (TextMessage)message; ...