Writing the Client Programs for the Asynchronous Receive Example

The sending program is producer/src/java/Producer.java, the same program used in the example in A Simple Example of Synchronous Message Receives.

An asynchronous consumer normally runs indefinitely. This one runs until the user types the letter q or Q to stop the program.

The receiving program, asynchconsumer/src/java/AsynchConsumer.java, performs the following steps:

1. Injects resources for a connection factory, queue, and topic.

2. Assigns either the queue or topic to a destination object, based on the specified destination type.

3. Creates a Connection and a Session.

4. Creates a MessageConsumer.

5. Creates an instance of the TextListener class and registers it as the message listener for the MessageConsumer:

   listener = new TextListener();consumer.setMessageListener(listener);

6. Starts the connection, causing message delivery to begin.

7. Listens for the messages published to the destination, stopping when the user types the character q or Q:

   System.out.println("To end program, type Q or q, " + "then <return>");
   inputStreamReader = new InputStreamReader(System.in);
   while (!((answer == ’q’) || (answer == ’Q’))) { 
       try { 
           answer = (char) inputStreamReader.read(); 
       } catch (IOException e) { 
           System.out.println("I/O exception: " + e.toString()); 
       }
   }

8. Closes the connection, which automatically closes the session and MessageConsumer.

The message listener, asynchconsumer/src/java/TextListener.java, follows these steps:

1. When a message arrives, the onMessage method is called automatically.

2. The onMessage method converts the incoming message to a TextMessage and displays its content. If the message is not a text message, it reports this fact:

   public void onMessage(Message message) { 
       TextMessage msg = null; 
       try { 
           if (message instanceof TextMessage) { 
               msg = (TextMessage) message; 
                System.out.println("Reading message: " + msg.getText()); 
           } else { 
                System.out.println("Message is not a " + "TextMessage"); 
           } 
       } catch (JMSException e) { 
           System.out.println("JMSException in onMessage(): " + e.toString()); 
       } catch (Throwable t) { 
           System.out.println("Exception in onMessage():" + t.getMessage()); 
       }
   }

You will use the connection factory and destinations you created in Creating JMS Administered Objects for the Synchronous Receive Example.