Create message queue based chatter using JMS - Java Message

Java examples for Message:JMS

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Description

Create message queue based chatter using JMS

Demo Code


import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import javax.jms.*;
import javax.naming.Context;
import javax.naming.InitialContext;
import java.util.Scanner;

public class TransactedChat {

  private static final Log LOG = LogFactory.getLog(TransactedChat.class);
  private static final Boolean NON_TRANSACTED = false;
  private static final Boolean TRANSACTED = true;
  private static final String CONNECTION_FACTORY_NAME = "myJmsFactory";
  private static final String DESTINATION_NAME = "topic/chat";
  private static final long MESSAGE_LIFESPAN = 30 * 60 * 1000; // 30 minutes

  public static void main(String[] args) {
    Connection connection = null;
    try {/*from www .  j a v  a 2  s  . c  o m*/
      // start up an init context... properties file must be named "jndi.properties"
      // on the root
      // of the classpath
      Context context = new InitialContext();
      ConnectionFactory factory = (ConnectionFactory) context.lookup(CONNECTION_FACTORY_NAME);
      Topic destination = (Topic) context.lookup(DESTINATION_NAME);

      connection = factory.createConnection();

      String chatter = System.getProperty("ChatName");
      connection.setClientID(chatter);

      Session pubSession = connection.createSession(TRANSACTED, Session.AUTO_ACKNOWLEDGE);
      MessageProducer publisher = pubSession.createProducer(destination);

      Session subSession = connection.createSession(NON_TRANSACTED, Session.AUTO_ACKNOWLEDGE);
      MessageConsumer subscriber = subSession.createConsumer(destination);

      subscriber.setMessageListener(new MessageListener() {
        @Override
        public void onMessage(Message message) {
          try {
            if (message instanceof TextMessage) {
              TextMessage textMessage = (TextMessage) message;
              String text = textMessage.getText();
              System.out.println("RECEIVED >> '" + text + "'");
            }
          } catch (JMSException e) {
            LOG.error("Got an JMSException handling message: " + message, e);
          }
        }
      });

      System.out.println("The application user " + chatter + " connects to the broker.\n"
          + "The application will stage messages to the " + destination.toString()
          + " topic until you either commit them or roll them back.\n"
          + "The application also subscribes to that topic to consume any committed messages published there.\n\n"
          + "1. Enter text to publish and then press Enter to stage the message.\n"
          + "2. Add a few messages to the transaction batch.\n" + "3. Then, either:\n"
          + "     o Enter the text 'COMMIT', and press Enter to publish all the staged messages.\n"
          + "     o Enter the text 'CANCEL', and press Enter to drop the staged messages waiting to be sent.\n\n");

      // start the connection AFTER the sout because if there are pending messages
      // they would get printed
      // before the direction statement
      connection.start();

      Scanner inputReader = new Scanner(System.in);

      while (true) {
        String line = inputReader.nextLine();
        if (line == null) {
          LOG.info("No Line -> Exit this chat");
          break;
        } else if (line.length() > 0) {
          if (line.trim().equals("CANCEL")) {
            System.out.println("Cancelling messages...");
            pubSession.rollback();
            System.out.println("Staged messages have been cleared");
          } else if (line.trim().equals("COMMIT")) {
            System.out.println("Comitting messages...");
            pubSession.commit();
            System.out.println("Staged messages have been sent");
          } else {
            try {
              TextMessage message = pubSession.createTextMessage();
              message.setText(chatter + ": " + line);
              System.out.println("SEND >> '" + message.getText() + "'");

              // why is this set to persistent?
              publisher.send(message, DeliveryMode.PERSISTENT, Message.DEFAULT_PRIORITY, MESSAGE_LIFESPAN);
            } catch (JMSException e) {
              LOG.error("Exception during publishing a message: ", e);
            }
          }
        }
      }

      subscriber.close();
      subSession.close();
      publisher.close();
      pubSession.close();

    } catch (Exception e) {
      LOG.error(e);
    } finally {
      // got to clean up the connections and other resources!
      if (connection != null) {
        try {
          connection.close();
        } catch (JMSException e) {
          LOG.error(e);
        }
      }
    }

  }

}

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