javax.jms.TopicRequestor Maven / Gradle / Ivy
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package javax.jms;
/** The {@code TopicRequestor} helper class simplifies
* making service requests.
*
* The {@code TopicRequestor} constructor is given a non-transacted
* {@code TopicSession} and a destination {@code Topic}. It creates a
* {@code TemporaryTopic} for the responses and provides a
* {@code request} method that sends the request message and waits
* for its reply.
*
* This is a very basic request/reply abstraction which assumes the session
* is non-transacted with a delivery mode of either AUTO_ACKNOWLEDGE or
* DUPS_OK_ACKNOWLEDGE. It is expected that most applications will create
* less basic implementations.
*
* @see javax.jms.QueueRequestor
*
* @version JMS 2.0
* @since JMS 1.0
*
*/
public class TopicRequestor {
TopicSession session; // The topic session the topic belongs to.
TemporaryTopic tempTopic;
TopicPublisher publisher;
TopicSubscriber subscriber;
/** Constructor for the {@code TopicRequestor} class.
*
*
This implementation assumes the session parameter to be non-transacted,
* with a delivery mode of either {@code AUTO_ACKNOWLEDGE} or
* {@code DUPS_OK_ACKNOWLEDGE}.
*
* @param session the {@code TopicSession} the topic belongs to
* @param topic the topic to perform the request/reply call on
*
* @exception JMSException if the JMS provider fails to create the
* {@code TopicRequestor} due to some internal
* error.
* @exception InvalidDestinationException if an invalid topic is specified.
*/
public
TopicRequestor(TopicSession session, Topic topic) throws JMSException {
if (topic==null) throw new InvalidDestinationException("topic==null");
this.session = session;
tempTopic = session.createTemporaryTopic();
publisher = session.createPublisher(topic);
subscriber = session.createSubscriber(tempTopic);
}
/** Sends a request and waits for a reply. The temporary topic is used for
* the {@code JMSReplyTo} destination; the first reply is returned,
* and any following replies are discarded.
*
* @param message the message to send
*
* @return the reply message
*
* @exception JMSException if the JMS provider fails to complete the
* request due to some internal error.
*/
public Message
request(Message message) throws JMSException {
message.setJMSReplyTo(tempTopic);
publisher.publish(message);
return(subscriber.receive());
}
/** Closes the {@code TopicRequestor} and its session.
*
*
Since a provider may allocate some resources on behalf of a
* {@code TopicRequestor} outside the Java virtual machine, clients
* should close them when they
* are not needed. Relying on garbage collection to eventually reclaim
* these resources may not be timely enough.
*
*
Note that this method closes the {@code TopicSession} object
* passed to the {@code TopicRequestor} constructor.
*
* @exception JMSException if the JMS provider fails to close the
* {@code TopicRequestor} due to some internal
* error.
*/
public void
close() throws JMSException {
// publisher and consumer created by constructor are implicitly closed.
session.close();
tempTopic.delete();
}
}