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/*
 * Copyright (c) 1997, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

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 Jakarta Messaging 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 Jakarta Messaging 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 Jakarta Messaging 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 Jakarta Messaging 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(); } }





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