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; ...
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