Create a Message Listener for Asynchronous Message Consumption

EMS allows a Message Consumer to consume messages either synchronously or asynchronously. For synchronous consumption, the Message Consumer explicitly calls a receive method on the topic or queue. For asynchronous consumption, you can implement a Message Listener that serves as an asynchronous event handler for messages.

A Message Listener implementation has one method, onMessage, that is called by the EMS server when a message arrives on a destination. You implement the onMessage method to perform the desired actions when a message arrives. Your implementation should handle all exceptions, and it should not throw any exceptions.

Once you create a Message Listener, you must register it with a specific Message Consumer before calling the connection’s start method to begin receiving messages.

A Message Listener is not specific to the type of the destination. The same listener can obtain messages from a queue or a topic, depending upon the destination set for the Message Consumer with which the listener is registered.

Note: The J2EE 1.3 platform introduced message-driven beans (MDBs) that are a special kind of Message Listener. See the J2EE documentation for more information about MDBs.
  • Java
       public class tibjmsAsyncMsgConsumer implements MessageListener
       {
          /* Create a connection, session and consumer */
       ...
          MessageConsumer QueueReceiver =                             session.createConsumer(queue);
          QueueReceiver.setMessageListener(this);
          connection.start();
       }
       public void onMessage(Message message)
       {
            /* Process message and handle exceptions */
       }

    See the tibjmsAsyncMsgConsumer.java sample client for a working example.

  • C
       void onMessage(tibemsMsgConsumer QueueReceiver,
                 tibemsMsg message, void* closure)
       {
            /* Process message and handle exceptions */
       }

    In another function, that creates a tibemsMsgConsumer and uses the tibemsMsgConsumer_SetMsgListener function to create a message listener for the Message Consumer, specifying onMessage() as the callback function:

    void run() 
    {
       tibemsMsgConsumer QueueReceiver = NULL;
       /* Create a connection, session and consumer */
       ...
       status = tibemsSession_CreateConsumer(session,
                     &QueueReceiver, queue, NULL, TIBEMS_FALSE);
       status = tibemsMsgConsumer_SetMsgListener(QueueReceiver,                  onMessage, NULL);
       status = tibemsConnection_Start(connection);
    }

    See the tibemsAsyncMsgConsumer.c sample client for a working example.

  • C#
       public class csAsyncMsgConsumer : IMessageListener
       {
          /* Create a connection, session and consumer */
       ...
          MessageConsumer QueueReceiver =                   session.CreateConsumer(queue);
          QueueReceiver.MessageListener = this;
          connection.Start();
       }
       public void OnMessage(Message message) {
          try
          {
               /* Process message and handle exceptions */
          }
       }

    See the csAsyncMsgConsumer.cs and csAsyncMsgConsumerUsingDelegate.cs sample clients for working examples.