IBM MQ listener service - onMessage not getting triggered

Question

I want to read messages from IBM MQ and just print them.

//my main class

import javax.jms.JMSException;
import javax.jms.MessageConsumer;
import javax.jms.Queue;
import javax.jms.Session;

import com.ibm.mq.jms.MQQueue;
import com.ibm.mq.jms.MQQueueConnection;
import com.ibm.mq.jms.MQQueueConnectionFactory;
import com.ibm.mq.jms.MQQueueSession;
import com.ibm.msg.client.wmq.WMQConstants;

public class QueueConnector {
    public static void main(String[] args) throws JMSException {
        MQQueueConnectionFactory qcf = new MQQueueConnectionFactory();
        MQQueueConnection qc;
        Queue queue;
        MQQueueSession queueSession;
        MessageConsumer consumer;
        qcf.setHostName ("XYZ");
        qcf.setPort (Integer.parseInt("abc"));
        qcf.setQueueManager ("ABC");
        qcf.setChannel ("IJK");
        qcf.setTransportType (WMQConstants.WMQ_CM_CLIENT);
        qc = (MQQueueConnection) qcf.createQueueConnection ();
        queue = new MQQueue("QUEUE_NAME");
        queueSession = (MQQueueSession) qc.createQueueSession (false,Session.AUTO_ACKNOWLEDGE);
        consumer = queueSession.createConsumer(queue);
        Listener listener = new Listener();
        consumer.setMessageListener(listener);
        qc.start();
    }
}

// listener class

import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.TextMessage;

public class Listener implements MessageListener {

    @Override
    public void onMessage(Message message) {
        // TODO Auto-generated method stub
        try {
            System.out.println(((TextMessage)message).getText());
        } catch (JMSException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("From Listener!");

    }
}

The main class is getting terminated without calling onMessage, even if there are messages in queue. Can anyone help me with this.

Answer 1

You need to keep your program running. When you reach the end of main - the program will exit and hence your listener won't fire.

Try placing new Scanner(System.in).nextLine(); at the end of your method to verify that it works. Of course, you may want to change this exit condition to something more appropriate (or actually close the scanner).