Need help: Using JMS to callback a client.

Question

Hi everyone,
I'm having a very frustrating problem. I'm just started to use JMS to overcome callback
problem with EJBs. I simply want my EJB to send something (pub/sub) to my client so it
can update some display. I first instantiate my Client and TopicConnection etc. etc. then
create the EJB, invoke it and the EJB sends some TextMessage back. However, the TextMessage
never seems to arrive at my Client. The TextListener never seems to deliver.
Here's the snippet:
EJB:
private void createPublisher() {
try {
Context ctx = new InitialContext();
System.out.println("Server looking up JMS Service");
TopicConnectionFactory conFtry = (TopicConnectionFactory) ctx.lookup("java:com
p/env/jms/MobiDTopicConnectionFactory");
topic = (Topic) ctx.lookup("java:comp/env/jms/TopicName");
con = conFtry.createTopicConnection();
session = con.createTopicSession(false, Session.AUTO_ACKNOWLEDGE);
publisher = session.createPublisher(topic);
TextMessage mesg = session.createTextMessage();
System.out.println("Server is sending message, see anything?");
mesg.setText("This is from publisher");
publisher.publish(mesg);
// Exception catching stuff snipped.
public void ejbCreate() { createPublisher(); }
Client:
public void createSubscriber() {
try {
Context ctx = new InitialContext();
TopicConnectionFactory conFtry = (TopicConnectionFactory) ctx.lookup("java:com
p/env/jms/MobiDTopicConnectionFactory");
Topic topic = (Topic) ctx.lookup("java:comp/env/jms/TopicName");
con = conFtry.createTopicConnection();
session = con.createTopicSession(false, Session.AUTO_ACKNOWLEDGE);
subscriber = session.createSubscriber(topic);
subscriber.setMessageListener(new TextListener());
con.start();
System.out.println("Connection started");
// Exception stuff snipped.
public static void main(String args[]) {
try {
ConverterClient cc = new ConverterClient();
cc.createSubscriber();
System.out.println("Subscriber is ready");
Context initial = new InitialContext();
System.out.println("Looking up the bean...");
Object ref = initial.lookup("java:comp/env/ejb/SimpleConverter");
System.out.println("Getting the home interface");
ConverterHome home = (ConverterHome) PortableRemoteObject.narrow(ref,
ConverterHome.class);
Converter conv = home.create();
double amount = conv.dollarToYen(100.00);
InputStreamReader inputStreamReader = new InputStreamReader(System.in);
char answer = '\0';
while (!((answer == 'q') || (answer == 'Q'))) {
try {
answer = (char) inputStreamReader.read();
} catch (IOException e) {
System.out.println("I/O exception: "
+ e.toString());
Can anyone spot what's wrong with the code? I've been trying to get this to work for the
past two days but to no avail. Please help...
Thank you in advance.
-vincent

Answer 1

Hi, thanks for all your reply.
The TextListener is the one downloaded from this website in the
tutorial but I used it in different program. Here's the TextListener:
public void onMessage(Message message) {
System.out.println("Receiving message in onMessage()");
TextMessage msg = null;
try {
if (message instanceof TextMessage) {
msg = (TextMessage) message;
System.out.println("Reading message: " +
msg.getText());
} else {
System.out.println("Message of wrong type: " +
message.getClass().getName());
} catch (JMSException e) {
System.out.println("JMSException in onMessage(): " +
e.toString());
} catch (Throwable t) {
System.out.println("Exception in onMessage():" +
t.getMessage());
Strangely, this does not work as it never print the message. Can't see what's
wrong from a glance though and I'm not getting any error message whatsoever.
However, I tried my own listener:
static class MyListener implements MessageListener {
public MyListener() { }
public void onMessage(Message msg) {
try {
System.out.println("Message received: " + ((TextMessage) msg).getText())
catch(JMSException ex) { ex.printStackTrace(); }
And this works...I just don't get it. MyListener is a static because I used it in my main().
Anyone can give any comment?
thanks,
-vincent