durablesubscriberexample.java

JMS的例子程序

/*
 * @(#)DurableSubscriberExample.java	1.6 00/08/18
 * 
 * Copyright (c) 2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
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 * modify and redistribute this software in source and binary code form,
 * provided that i) this copyright notice and license appear on all copies of
 * the software; and ii) Licensee does not utilize the software in a manner
 * which is disparaging to Sun.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY
 * IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR
 * NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE
 * LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
 * OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS
 * LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT,
 * INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER
 * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF
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 *
 * This software is not designed or intended for use in on-line control of
 * aircraft, air traffic, aircraft navigation or aircraft communications; or in
 * the design, construction, operation or maintenance of any nuclear
 * facility. Licensee represents and warrants that it will not use or
 * redistribute the Software for such purposes.
 */
import javax.jms.*;

/**
 * The DurableSubscriberExample class demonstrates that a durable subscription
 * is active even when the subscriber is not active.
 * <p>
 * The program contains a DurableSubscriber class, a MultiplePublisher class, 
 * a main method, and a method that instantiates the classes and calls their
 * methods in sequence.
 * <p>
 * The program begins like any publish/subscribe program: the subscriber starts,
 * the publisher publishes some messages, and the subscriber receives them.
 * <p>
 * At this point the subscriber closes itself.  The publisher then publishes 
 * some messages while the subscriber is not active.  The subscriber then 
 * restarts and receives the messages.
 * <p>
 * Specify a topic name on the command line when you run the program.
 *
 * @author Kim Haase
 * @version 1.6, 08/18/00
 */
public class DurableSubscriberExample {
    String      topicName = null;
    int         exitResult = 0;
    static int  startindex = 0;

    /**
     * The DurableSubscriber class contains a constructor, a startSubscriber 
     * method, a closeSubscriber method, and a finish method.
     * <p>
     * The class fetches messages asynchronously, using a message listener, 
     * TextListener.
     *
     * @author Kim Haase
     * @version 1.6, 08/18/00
     */
    public class DurableSubscriber {
        TopicConnection  topicConnection = null;
        TopicSession     topicSession = null;
        Topic            topic = null;
        TopicSubscriber  topicSubscriber = null;
        TextListener     topicListener = null;

        /**
         * The TextListener class implements the MessageListener interface by 
         * defining an onMessage method for the DurableSubscriber class.
         *
         * @author Kim Haase
         * @version 1.6, 08/18/00
         */
        private class TextListener implements MessageListener {
            final SampleUtilities.DoneLatch  monitor =
                new SampleUtilities.DoneLatch();

            /**
             * Casts the message to a TextMessage and displays its text.
             * A non-text message is interpreted as the end of the message 
             * stream, and the message listener sets its monitor state to all 
             * done processing messages.
             *
             * @param message	the incoming message
             */
            public void onMessage(Message message) {
                if (message instanceof TextMessage) {
                    TextMessage  msg = (TextMessage) message;
                    
                    try {
                        System.out.println("SUBSCRIBER: Reading message: " 
                                           + msg.getText());
                    } catch (JMSException e) {
                        System.out.println("Exception in onMessage(): " 
                                           + e.toString());
                    }
                } else {
                    monitor.allDone();
                }
            }
        }

        /**
         * Constructor: looks up a connection factory and topic and creates a 
         * connection and session.
         */
        public DurableSubscriber() {
            TopicConnectionFactory  topicConnectionFactory = null;

            try {
                topicConnectionFactory = 
                    SampleUtilities.getTopicConnectionFactory();
                topicConnection = 
                    topicConnectionFactory.createTopicConnection();
                topicConnection.setClientID("DurableSubscriberExample");
                topicSession = topicConnection.createTopicSession(false, 
                    Session.AUTO_ACKNOWLEDGE);
                topic = SampleUtilities.getTopic(topicName, topicSession);
            } catch (Exception e) {
                System.out.println("Connection problem: " + e.toString());
                if (topicConnection != null) {
                    try {
                        topicConnection.close();
                    } catch (JMSException ee) {}
                }
    	        System.exit(1);
            } 
        }

        /**
         * Stops connection, then creates durable subscriber, registers message 
         * listener (TextListener), and starts message delivery; listener
         * displays the messages obtained.
         */
        public void startSubscriber() {
            try {
                System.out.println("Starting subscriber");
                topicConnection.stop();
                topicSubscriber = topicSession.createDurableSubscriber(topic,
                    "MakeItLast");
                topicListener = new TextListener();
                topicSubscriber.setMessageListener(topicListener);
                topicConnection.start();
            } catch (JMSException e) {
                System.out.println("Exception occurred: " + e.toString());
                exitResult = 1;
            }
        }
        
        /**
         * Blocks until publisher issues a control message indicating
         * end of publish stream, then closes subscriber.
         */
        public void closeSubscriber() {
            try {
                topicListener.monitor.waitTillDone();
                System.out.println("Closing subscriber");
                topicSubscriber.close();
            } catch (JMSException e) {
                System.out.println("Exception occurred: " + e.toString());
                exitResult = 1;
            }
        }
        
        /**
         * Closes the connection.
         */
        public void finish() {
            if (topicConnection != null) {
                try {
                    topicSession.unsubscribe("MakeItLast");
                    topicConnection.close();
                } catch (JMSException e) {
                    exitResult = 1;
                }
            }
        }
    }

    /**
     * The MultiplePublisher class publishes several messages to a topic. It
     * contains a constructor, a publishMessages method, and a finish method.
     *
     * @author Kim Haase
     * @version 1.6, 08/18/00
     */
    public class MultiplePublisher {
        TopicConnection  topicConnection = null;
        TopicSession     topicSession = null;
        Topic            topic = null;
        TopicPublisher   topicPublisher = null;

        /**
         * Constructor: looks up a connection factory and topic and creates a 
         * connection and session.  Also creates the publisher.
         */
        public MultiplePublisher() {
            TopicConnectionFactory  topicConnectionFactory = null;

            try {
                topicConnectionFactory = 
                    SampleUtilities.getTopicConnectionFactory();
                topicConnection = 
                    topicConnectionFactory.createTopicConnection();
                topicSession = topicConnection.createTopicSession(false, 
                    Session.AUTO_ACKNOWLEDGE);
                topic = SampleUtilities.getTopic(topicName, topicSession);
                topicPublisher = topicSession.createPublisher(topic);
            } catch (Exception e) {
                System.out.println("Connection problem: " + e.toString());
                if (topicConnection != null) {
                    try {
                        topicConnection.close();
                    } catch (JMSException ee) {}
                }
    	        System.exit(1);
            } 
        }
        
        /**
         * Creates text message.
         * Sends some messages, varying text slightly.
         * Messages must be persistent.
         */
        public void publishMessages() {
            TextMessage   message = null;
            int           i;
            final int     NUMMSGS = 3;
            final String  MSG_TEXT = new String("Here is a message");

            try {
                message = topicSession.createTextMessage();
                for (i = startindex; i < startindex + NUMMSGS; i++) {
                    message.setText(MSG_TEXT + " " + (i + 1));
                    System.out.println("PUBLISHER: Publishing message: " 
                        + message.getText());
                    topicPublisher.publish(message);
                }

                // Send a non-text control message indicating end of messages.
                topicPublisher.publish(topicSession.createMessage());
                startindex = i;
            } catch (JMSException e) {
                System.out.println("Exception occurred: " + e.toString());
                exitResult = 1;
            }
        }
        
        /**
         * Closes the connection.
         */
        public void finish() {
            if (topicConnection != null) {
                try {
                    topicConnection.close();
                } catch (JMSException e) {
                    exitResult = 1;
                }
            }
        }
    }
    
    /**
     * Instantiates the subscriber and publisher classes.
     *
     * Starts the subscriber; the publisher publishes some messages.
     *
     * Closes the subscriber; while it is closed, the publisher publishes
     * some more messages.
     *
     * Restarts the subscriber and fetches the messages.
     *
     * Finally, closes the connections.    
     */
    public void run_program() {
        DurableSubscriber  durableSubscriber = new DurableSubscriber();
        MultiplePublisher  multiplePublisher = new MultiplePublisher();

        durableSubscriber.startSubscriber();
        multiplePublisher.publishMessages();
        durableSubscriber.closeSubscriber();
        multiplePublisher.publishMessages();
        durableSubscriber.startSubscriber();
        durableSubscriber.closeSubscriber();
        multiplePublisher.finish();
        durableSubscriber.finish();
    }

    /**
     * Reads the topic name from the command line, then calls the
     * run_program method.
     *
     * @param args	the topic used by the example
     */
    public static void main(String[] args) {
        DurableSubscriberExample  dse = new DurableSubscriberExample();
        
        if (args.length != 1) {
    	    System.out.println("Usage: java DurableSubscriberExample <topic_name>");
    	    System.exit(1);
    	}
        dse.topicName = new String(args[0]);
        System.out.println("Topic name is " + dse.topicName);

    	dse.run_program();
    	SampleUtilities.exit(dse.exitResult);
    }
}