TopicRequestor.java

/*
 * The contents of this file are subject to the terms
 * of the Common Development and Distribution License
 * (the License).  You may not use this file except in
 * compliance with the License.
 *
 * You can obtain a copy of the license at
 * https://glassfish.dev.java.net/public/CDDLv1.0.html or
 * glassfish/bootstrap/legal/CDDLv1.0.txt.
 * See the License for the specific language governing
 * permissions and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL
 * Header Notice in each file and include the License file
 * at glassfish/bootstrap/legal/CDDLv1.0.txt.
 * If applicable, add the following below the CDDL Header,
 * with the fields enclosed by brackets [] replaced by
 * you own identifying information:
 * "Portions Copyrighted [year] [name of copyright owner]"
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 */

package javax.jms;

/** The <CODE>TopicRequestor</CODE> helper class simplifies
 * making service requests.
 *
 * <P>The <CODE>TopicRequestor</CODE> constructor is given a non-transacted
 * <CODE>TopicSession</CODE> and a destination <CODE>Topic</CODE>. It creates a
 * <CODE>TemporaryTopic</CODE> for the responses and provides a
 * <CODE>request</CODE> method that sends the request message and waits
 * for its reply.
 *
 * <P>This is a basic request/reply abstraction that should be sufficient
 * for most uses. JMS providers and clients are free to create more
 * sophisticated versions.
 *
 * @version     1.0 - 8 July 1998
 * @author      Mark Hapner
 * @author      Rich Burridge
 *
 * @see         javax.jms.QueueRequestor
 */

public class TopicRequestor
{

  TopicSession session; // The topic session the topic belongs to.

  Topic topic; // The topic to perform the request/reply on.

  TemporaryTopic tempTopic;

  TopicPublisher publisher;

  TopicSubscriber subscriber;

  /** Constructor for the <CODE>TopicRequestor</CODE> class.
    *
    * <P>This implementation assumes the session parameter to be non-transacted,
    * with a delivery mode of either <CODE>AUTO_ACKNOWLEDGE</CODE> or
    * <CODE>DUPS_OK_ACKNOWLEDGE</CODE>.
    *
    * @param session the <CODE>TopicSession</CODE> 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</CODE> due to some internal
    *                         error.
    * @exception InvalidDestinationException if an invalid topic is specified.
    */

  public TopicRequestor(TopicSession session, Topic topic) throws JMSException
  {
    this.session = session;
    this.topic = topic;
    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</CODE> 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</CODE> and its session.
    *
    * <P>Since a provider may allocate some resources on behalf of a
    * <CODE>TopicRequestor</CODE> 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.
    *
    * <P>Note that this method closes the <CODE>TopicSession</CODE> object
    * passed to the <CODE>TopicRequestor</CODE> constructor.
    *
    * @exception JMSException if the JMS provider fails to close the
    *                         <CODE>TopicRequestor</CODE> due to some internal
    *                         error.
    */

  public void close() throws JMSException
  {

    // publisher and consumer created by constructor are implicitly closed.
    session.close();
    tempTopic.delete();
  }
}