Unable to consume messages or only one message is getting retrieved while connecting to IBM MQ async

[Venkat S Prasad]

I had written a java code to consume messages from IBM MQ.. but while executing the code some times only one message is getting consumed and the process is stopping .. some times no messages are not getting consumed at all.. i had written an asynchronous connection using setMessageListener() but i am not sure where the program is getting wrong, the main method is getting terminated automatically. The below code

public class MQConnectivity implements MessageListener {
    
    MQQueueConnectionFactory factory = new MQQueueConnectionFactory();
    QueueConnection con;
    Queue queue;
    QueueSession session;
    QueueReceiver receiver;
    
    public void init() {
        try {
            factory.setHostName("******");
            factory.setPort(123);
            factory.setChannel("Channel1");
            factory.setQueueManager("queue_manager");
            factory.setTransportType(new Integer(WMQConstants.WMQ_CM_CLIENT));
            con=factory.createQueueConnection("user1"," password1");
            queue= new MQQueue("myQueue");
            session=con.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
            receiver=session.createReceiver(queue);
            receiver.setMessageListener(this);
            System.out.println("=======connection happened=========");
            con.start();
            System.out.println("=======connection started=========");
        }catch(Exception ex) {
            System.out.println("exception is : "+ex);
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new MQConnectivity().init();

    }
    @Override
    public void onMessage(Message msg) {
        // TODO Auto-generated method stub
        try {
        System.out.println("Inside onMessage method");
        TextMessage txtMsg=(TextMessage)msg;
        System.out.println(txtMsg.getText());
        }catch(Exception ex) {
            System.out.println("error in onMessage"+ex);
        }
    }

}

But writing  System.in.read() it is consuming messages continuously until an input from system.. but tis is not the right process to deploy the code in production.. please help me in this

[Tim Holloway]

I can't answer your main question, but in Enterprise Java, the System.in/out/err streams are almost never the right answer. In webapps, for example, those streams technically don't exist and there's no telling where the webapp server will send them.

For System out/err, it is better to use logging. System.in usually isn't useful at all.

[Venkat S Prasad]

I had used Thread.Sleep() as well to check if the system is working , it is working but only for the time mentioned in the sleep method only.. but he main method needs to run continuously without any halt

[Tim Holloway]

Venkat S Prasad wrote:I had used Thread.Sleep() as well to check if the system is working , it is working but only for the time mentioned in the sleep method only.. but he main method needs to run continuously without any halt

That's another questionable item. Directly manipulating threads in JEE apps is often a problem. In fact, returning to the JEE webapp environment the JEE spec absolutely forbids spawing threads or doing other thread operations on servlet service methods or Enterprise JavaBeans.

[Venkat S Prasad]

Tim Holloway wrote:

Venkat S Prasad wrote:I had used Thread.Sleep() as well to check if the system is working , it is working but only for the time mentioned in the sleep method only.. but he main method needs to run continuously without any halt

That's another questionable item. Directly manipulating threads in JEE apps is often a problem. In fact, returning to the JEE webapp environment the JEE spec absolutely forbids spawing threads or doing other thread operations on servlet service methods or Enterprise JavaBeans.

One thing what i want to mention is this is not a JEE app.. it is a simple java application where i am trying to consuming the messages

[Tim Holloway]

Actually, JMS is part of JEE, so any app that employs JMS is a JEE app. However as a MQ client, some of what you're doing would be allowable (if not always recommended) where it wouldn't be for server-side code.

A simple MQ client shouldn't be playing around with threading, though. All it needs to do is listen for incoming messages. My memory is a bit fuzzy on how received messages get handled - whether asynchronously, synchonously, or optional selection, but in any case any threads spawned by the MQ client methods should not be interfered with by you. Just do the work and return.

Messages to System.out or logs are OK in a multi-threaded system no matter what's doing the thread control. However, the order in which messages are output may vary.

[Al Hobbs]

It seems like he is making a console app and wants to print the messages.  He wants to know how to make it not exit without using System.in.read().  

How about a while loop?

[Paul Clapham]

Venkat S Prasad wrote:but he main method needs to run continuously without any halt

No, the main method should just start the connection. Presumably that starts a thread which listens for messages and calls the onMessage() method for each message it receives. I don't see how calling Thread.sleep should affect anything. Perhaps you could explain a bit more about how you know that the whole application (not just the main method) is stopping.

[Paul Clapham]

Also... to know that the application is terminating, you can add a shutdown hook which can tell you that. Here's a tutorial which shows you how to do that.

[Venkat S Prasad]

Paul Clapham wrote:Also... to know that the application is terminating, you can add a shutdown hook which can tell you that. Here's a tutorial which shows you how to do that.

Thanks for your reply.. by seeing my code could you please guess  why my init() method is returning back to main method without calling onMessage() when there are lot of messages that need to be processed.. it should not happen in this case ight.. as it is a asynchronous process the onMessag needs to be calledtill the last message gets consumed and then return to main method

[Venkat S Prasad]

Paul Clapham wrote:

Venkat S Prasad wrote:but he main method needs to run continuously without any halt

No, the main method should just start the connection. Presumably that starts a thread which listens for messages and calls the onMessage() method for each message it receives. I don't see how calling Thread.sleep should affect anything. Perhaps you could explain a bit more about how you know that the whole application (not just the main method) is stopping.

Thanks for your reply.. by seeing my code could you please guess  why my init() method is returning back to main method without calling onMessage() when there are lot of messages that need to be consumed.. it should not happen in this case ight.. as it is a asynchronous process the onMessag needs to be calledtill the last message gets consumed and then return to main method.

As per your request in any message consumer class when ever any message listener starts it needs to start consuming or producing any messages immediately but it is not happening in this case , it is just going back to the previous call where the init method has been called.. but if i keep Thread.sleep it is consuming the messages in that time where the main method has been waiting stae and then quitting.. i want to know  why after starting connection it is taking time to connect to onMessage method

[Al Hobbs]

try this

   public static void main(String[] args) {
        // TODO Auto-generated method stub
        MQConnectivity mc = new MQConnectivity();
        mc.init();

        while(true)  {
             // break this when all messages are consumed.
        }
     }

onMessage is called asynchronously whenever there is a message.
After you call init() the program ends, so no messages are consumed or maybe 1 if it arrives before it exits.

[Paul Clapham]

Venkat S Prasad wrote:Thanks for your reply.. by seeing my code could you please guess  why my init() method is returning back to main method without calling onMessage() when there are lot of messages that need to be consumed.. it should not happen in this case ight.. as it is a asynchronous process the onMessag needs to be calledtill the last message gets consumed and then return to main method.

As per your request in any message consumer class when ever any message listener starts it needs to start consuming or producing any messages immediately but it is not happening in this case , it is just going back to the previous call where the init method has been called.. but if i keep Thread.sleep it is consuming the messages in that time where the main method has been waiting stae and then quitting.. i want to know  why after starting connection it is taking time to connect to onMessage method

First of all your init() method does not call onMessage(). It creates a thread which connects to the MQ server to ask it for messages which may be waiting. As for why it takes time to connect, the thread must connect to the MQ server over the network, perhaps even to a server on a different machine. Such things do not happen instantaneously.

What was the result when you added a shutdown hook to your code? Did it run almost immediately? Or did it not run at all?

[Venkat S Prasad]

Al Hobbs wrote:try this

   public static void main(String[] args) {
        // TODO Auto-generated method stub
        MQConnectivity mc = new MQConnectivity();
        mc.init();

        while(true)  {
             // break this when all messages are consumed.
        }
     }

onMessage is called asynchronously whenever there is a message.
After you call init() the program ends, so no messages are consumed or maybe 1 if it arrives before it exits.

Thanks .. it Worked but the messages that are consumed are not in an order .. example if three messages gets consumed .. in that two messages prints the message in logs and then they are hitting database .. it is creating a problem

[Paul Clapham]

Venkat S Prasad wrote:Thanks .. it Worked but the messages that are consumed are not in an order .. example if three messages gets consumed .. in that two messages prints the message in logs and then they are hitting database .. it is creating a problem

It would be a good idea to describe that problem in a new post, then. It seems like a different problem than the one covered in this thread.

[Al Hobbs]

There may be a setting for that, or you would have to manually process them in order somehow