The Java EE 5 Tutorial (PDF) - Oracle Software Downloads

Writing Simple JMS Client Applications
916
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” on page 907.
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 ");
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());
The Java EE 5Tutorial • June 2010