The use of a message listener in the publish/subscribe model. The producer publishes several messages, and the consumer reads them asynchronously : Java消息服务JMS « J2EE平台 « Java

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Java » J2EE平台 » Java消息服务JMS屏幕截图 
The use of a message listener in the publish/subscribe model. The producer publishes several messages, and the consumer reads them asynchronously
 

/*
 * @(#)AsynchTopicExample.java  1.3 02/05/02
 *
 * Copyright (c) 2000-2002 Sun Microsystems, Inc. All Rights Reserved.
 
 * Sun grants you ("Licensee") a non-exclusive, royalty free, license to use,
 * 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
 * OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGES.
 *
 * 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 AsynchTopicExample class demonstrates the use of a message listener in 
 * the publish/subscribe model.  The producer publishes several messages, and
 * the consumer reads them asynchronously.
 * <p>
 * The program contains a MultipleProducer class, an AsynchConsumer class
 * with a listener class, a main method, and a method that runs the consumer
 * and producer threads.
 * <p>
 * Specify a topic name on the command line when you run the program.  The 
 * program also uses a queue named "controlQueue", which should be created  
 * before you run the program.
 *
 @author Kim Haase
 @version 1.6, 08/18/00
 */
public class AsynchTopicExample {
    final String  CONTROL_QUEUE = "controlQueue";
    String        topicName = null;
    int           exitResult = 0;

    /**
     * The AsynchConsumer class fetches several messages from a topic 
     * asynchronously, using a message listener, TextListener.
     *
     @author Kim Haase
     @version 1.6, 08/18/00
     */
    public class AsynchConsumer extends Thread {

        /**
         * The TextListener class implements the MessageListener interface by 
         * defining an onMessage method for the AsynchConsumer 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 = (TextMessagemessage;

                    try {
                        System.out.println("CONSUMER THREAD: Reading message: " 
                                           + msg.getText());
                    catch (JMSException e) {
                        System.out.println("Exception in onMessage(): " 
                                           + e.toString());
                    }
                else {
                    monitor.allDone();
                }
            }
        }

        /**
         * Runs the thread.
         */
        public void run() {
            ConnectionFactory    connectionFactory = null;
            Connection           connection = null;
            Session              session = null;
            Topic                topic = null;
            MessageConsumer      msgConsumer = null;
            TextListener         topicListener = null;

            try {
                connectionFactory = 
                    SampleUtilities.getConnectionFactory();
                connection = 
                    connectionFactory.createConnection();
                session = connection.createSession(false, 
                    Session.AUTO_ACKNOWLEDGE);
                topic = SampleUtilities.getTopic(topicName, session);
            catch (Exception e) {
                System.out.println("Connection problem: " + e.toString());
                if (connection != null) {
                    try {
                        connection.close();
                    catch (JMSException ee) {}
                }
              System.exit(1);
            

            /*
             * Create consumer.
             * Register message listener (TextListener).
             * Start message delivery.
             * Send synchronize message to producer, then wait till all
             * messages have arrived.
             * Listener displays the messages obtained.
             */
            try {
                msgConsumer = session.createConsumer(topic);
                topicListener = new TextListener();
                msgConsumer.setMessageListener(topicListener);
                connection.start();
                
                // Let producer know that consumer is ready.
                try {
                    SampleUtilities.sendSynchronizeMessage("CONSUMER THREAD: ",
                                                            CONTROL_QUEUE);
                catch (Exception e) {
                    System.out.println("Queue probably missing: " + e.toString());
                    if (connection != null) {
                        try {
                            connection.close();
                        catch (JMSException ee) {}
                    }
                  System.exit(1);
              }

                /*
                 * Asynchronously process messages.
                 * Block until producer issues a control message indicating
                 * end of publish stream.
                 */
                topicListener.monitor.waitTillDone();
            catch (JMSException e) {
                System.out.println("Exception occurred: " + e.toString());
                exitResult = 1;
            finally {
                if (connection != null) {
                    try {
                        connection.close();
                    catch (JMSException e) {
                        exitResult = 1;
                    }
                }
            }
        }      
    }

    /**
     * The MultipleProducer class publishes several message to a topic. 
     *
     @author Kim Haase
     @version 1.6, 08/18/00
     */
    public class MultipleProducer extends Thread {

        /**
         * Runs the thread.
         */
        public void run() {
            ConnectionFactory    connectionFactory = null;
            Connection           connection = null;
            Session              session = null;
            Topic                topic = null;
            MessageProducer      msgProducer = null;
            TextMessage          message = null;
            final int            NUMMSGS = 20;
            final String         MSG_TEXT = new String("Here is a message");

            try {
                connectionFactory = 
                    SampleUtilities.getConnectionFactory();
                connection = 
                    connectionFactory.createConnection();
                session = connection.createSession(false, 
                    Session.AUTO_ACKNOWLEDGE);
                topic = SampleUtilities.getTopic(topicName, session);
            catch (Exception e) {
                System.out.println("Connection problem: " + e.toString());
                if (connection != null) {
                    try {
                        connection.close();
                    catch (JMSException ee) {}
                }
              System.exit(1);
            

            /*
             * After synchronizing with consumer, create producer.
             * Create text message.
             * Send messages, varying text slightly.
             * Send end-of-messages message.
             * Finally, close connection.
             */
            try {
                /*
                 * Synchronize with consumer.  Wait for message indicating 
                 * that consumer is ready to receive messages.
                 */
                try {
                    SampleUtilities.receiveSynchronizeMessages("PRODUCER THREAD: ",
                                                              CONTROL_QUEUE, 1);
                catch (Exception e) {
                    System.out.println("Queue probably missing: " + e.toString());
                    if (connection != null) {
                        try {
                            connection.close();
                        catch (JMSException ee) {}
                    }
                  System.exit(1);
              }
                
                msgProducer = session.createProducer(topic);
                message = session.createTextMessage();
                for (int i = 0; i < NUMMSGS; i++) {
                    message.setText(MSG_TEXT + " " (i + 1));
                    System.out.println("PRODUCER THREAD: Publishing message: " 
                        + message.getText());
                    msgProducer.send(message);
                }

                // Send a non-text control message indicating end of messages.
                msgProducer.send(session.createMessage());
            catch (JMSException e) {
                System.out.println("Exception occurred: " + e.toString());
                exitResult = 1;
            finally {
                if (connection != null) {
                    try {
                        connection.close();
                    catch (JMSException e) {
                        exitResult = 1;
                    }
                }
            }
        }
    }
    
    /**
     * Instantiates the consumer and producer classes and starts their
     * threads.
     * Calls the join method to wait for the threads to die.
     * <p>
     * It is essential to start the consumer before starting the producer.
     * In the publish/subscribe model, a consumer can ordinarily receive only 
     * messages published while it is active.
     */
    public void run_threads() {
        AsynchConsumer   asynchConsumer = new AsynchConsumer();
        MultipleProducer  multipleProducer = new MultipleProducer();

        multipleProducer.start();
        asynchConsumer.start();
        try {
            asynchConsumer.join();
            multipleProducer.join();
        catch (InterruptedException e) {}
    }

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

      ate.run_threads();
      SampleUtilities.exit(ate.exitResult);
    }
}

        
jms.zip( 65 k)
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