PreacknowledgeExample.java

/*
 * Copyright 2009 Red Hat, Inc.
 * Red Hat licenses this file to you under the Apache License, version
 * 2.0 (the "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *    http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied.  See the License for the specific language governing
 * permissions and limitations under the License.
 */
package org.hornetq.jms.example;

import javax.jms.Connection;
import javax.jms.ConnectionFactory;
import javax.jms.Message;
import javax.jms.MessageConsumer;
import javax.jms.MessageProducer;
import javax.jms.Queue;
import javax.jms.QueueConnection;
import javax.jms.QueueRequestor;
import javax.jms.QueueSession;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.naming.InitialContext;

import org.hornetq.api.jms.HornetQJMSClient;
import org.hornetq.api.jms.HornetQJMSConstants;
import org.hornetq.api.jms.management.JMSManagementHelper;
import org.hornetq.common.example.HornetQExample;

/**
 * 
 * This example demonstrates the use of HornetQ "pre-acknowledge" functionality where
 * messages are acknowledged before they are delivered to the consumer.
 * 
 * Please see the readme.html for more details.
 *
 * @author <a href="mailto:tim.fox@jboss.com">Tim Fox</a>
 *
 */
public class PreacknowledgeExample extends HornetQExample
{
   public static void main(final String[] args)
   {
      new PreacknowledgeExample().run(args);
   }

   @Override
   public boolean runExample() throws Exception
   {
      Connection connection = null;

      InitialContext initialContext = null;
      try
      {
         // Step 1. Create an initial context to perform the JNDI lookup.
         initialContext = getContext(0);

         // Step 2. Perform the look-ups
         Queue queue = (Queue)initialContext.lookup("/queue/exampleQueue");

         ConnectionFactory cf = (ConnectionFactory)initialContext.lookup("/ConnectionFactory");

         // Step 3. Create a the JMS objects
         connection = cf.createConnection();

         Session session = connection.createSession(false, HornetQJMSConstants.PRE_ACKNOWLEDGE);

         MessageProducer producer = session.createProducer(queue);

         MessageConsumer messageConsumer = session.createConsumer(queue);

         // Step 4. Create and send a message
         TextMessage message1 = session.createTextMessage("This is a text message 1");

         producer.send(message1);

         System.out.println("Sent message: " + message1.getText());

         // Step 5. Print out the message count of the queue. The queue contains one message as expected
         // delivery has not yet started on the queue
         int count = getMessageCount(connection);

         System.out.println("Queue message count is " + count);

         // Step 6. Start the Connection, delivery will now start. Give a little time for delivery to occur.
         connection.start();

         Thread.sleep(1000);

         // Step 7. Print out the message countof the queue. It should now be zero, since the message has
         // already been acknowledged even before the consumer has received it.
         count = getMessageCount(connection);

         System.out.println("Queue message count is now " + count);

         if (count != 0)
         {
            return false;
         }

         // Step 8. Finally, receive the message
         TextMessage messageReceived = (TextMessage)messageConsumer.receive(5000);

         System.out.println("Received message: " + messageReceived.getText());

         return true;
      }
      finally
      {
         // Step 9. Be sure to close our resources!
         if (initialContext != null)
         {
            initialContext.close();
         }
         if (connection != null)
         {
            connection.close();
         }
      }
   }

   // To do this we send a management message to get the message count.
   // In real life you wouldn't create a new session every time you send a management message
   private int getMessageCount(final Connection connection) throws Exception
   {
      QueueSession session = ((QueueConnection)connection).createQueueSession(false, Session.AUTO_ACKNOWLEDGE);

      Queue managementQueue = HornetQJMSClient.createQueue("hornetq.management");

      QueueRequestor requestor = new QueueRequestor(session, managementQueue);

      connection.start();

      Message m = session.createMessage();

      JMSManagementHelper.putAttribute(m, "jms.queue.exampleQueue", "messageCount");

      Message response = requestor.request(m);

      int messageCount = (Integer)JMSManagementHelper.getResult(response);

      return messageCount;
   }

}