Now lets discuss about Asynchronous Receiver in Java Messaging Service (JMS)

One of the great benefit of receiving message asychronous is that receiver take care of receiving the message on its own as soon as the sender put the message in the queue.


package com.siddhu.receiver;
import java.util.Properties;

import javax.naming.Context;
import javax.naming.InitialContext;

import javax.jms.Queue;
import javax.jms.Session;
import javax.jms.Message;
import javax.jms.TextMessage;
import javax.jms.MessageListener;
import javax.jms.JMSException;
import javax.jms.ExceptionListener;
import javax.jms.QueueSession;
import javax.jms.QueueReceiver;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;

public class AsyncReceiver implements MessageListener, ExceptionListener
{
    static QueueConnection queueConn = null;
    public static void main(String[] args) throws Exception
    {
    Properties env = new Properties();
env.put(Context.INITIAL_CONTEXT_FACTORY,
"org.apache.activemq.jndi.ActiveMQInitialContextFactory");
env.put(Context.PROVIDER_URL, "tcp://localhost:61616");
env.put("queue.queueSampleQueue","MyNewQueue");

       // get the initial context
       InitialContext ctx = new InitialContext(env);

       // lookup the queue object
       Queue queue = (Queue) ctx.lookup("queueSampleQueue");

       // lookup the queue connection factory
       QueueConnectionFactory connFactory = (QueueConnectionFactory) ctx.lookup("QueueConnectionFactory");

       // create a queue connection
       queueConn = connFactory.createQueueConnection();

       // create a queue session
       QueueSession queueSession = queueConn.createQueueSession(false,Session.AUTO_ACKNOWLEDGE);

       // create a queue receiver
       QueueReceiver queueReceiver = queueSession.createReceiver(queue);

       // set an asynchronous message listener
       AsyncReceiver asyncReceiver = new AsyncReceiver();
       queueReceiver.setMessageListener(asyncReceiver);

       // set an asynchronous exception listener on the connection
       queueConn.setExceptionListener(asyncReceiver);

       // start the connection
       queueConn.start();
    }

    /**
       This method is called asynchronously by JMS when a message arrives
       at the queue. Client applications must not throw any exceptions in
       the onMessage method.
       @param message A JMS message.
     */
    public void onMessage(Message message)
    {
       TextMessage msg = (TextMessage) message;
       try {
      if(msg.getText().equals("exit")){
      queueConn.close();
      System.out.println("Application Exits");
      }else{
      System.out.println("received: " + msg.getText());
      }
       } catch (JMSException ex) {
          ex.printStackTrace();
       }
    }

    /**
       This method is called asynchronously by JMS when some error occurs.
       When using an asynchronous message listener it is recommended to use
       an exception listener also since JMS have no way to report errors
       otherwise.
       @param exception A JMS exception.
     */
    public void onException(JMSException exception)
    {
       System.err.println("an error occurred: " + exception);
    }
}

Send your message using Sender.java and also start your AsyncReceiver which will remaing in start mode until it is explicitly closed.

package com.siddhu.sender;
import java.util.Properties;

import javax.naming.Context;
import javax.naming.InitialContext;

import javax.jms.Queue;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.jms.QueueSender;
import javax.jms.DeliveryMode;
import javax.jms.QueueSession;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;

public class Sender {

public static void main(String[] args) throws Exception {
Properties env = new Properties();
env.put(Context.INITIAL_CONTEXT_FACTORY,
"org.apache.activemq.jndi.ActiveMQInitialContextFactory");
env.put(Context.PROVIDER_URL, "tcp://localhost:61616");
env.put("queue.queueSampleQueue", "MyNewQueue");

// get the initial context
InitialContext ctx = new InitialContext(env);

// lookup the queue object
Queue queue = (Queue) ctx.lookup("queueSampleQueue");
// lookup the queue connection factory
QueueConnectionFactory connFactory = (QueueConnectionFactory) ctx.lookup("QueueConnectionFactory");
// create a queue connection
QueueConnection queueConn = connFactory.createQueueConnection();

// create a queue session
QueueSession queueSession = queueConn.createQueueSession(false,Session.DUPS_OK_ACKNOWLEDGE);

// create a queue sender
QueueSender queueSender = queueSession.createSender(queue);
queueSender.setDeliveryMode(DeliveryMode.NON_PERSISTENT);

// create a simple message to say "Hello this is siddharatha"
TextMessage message = queueSession.createTextMessage("Hello this is siddharathass");

// send the message
queueSender.send(message);

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

queueConn.close();
}
}


Now try to send the multiple message and  you will see message is automtically received at the receiver end.