Hi, Thanks a lot for the suggestion. The fact that EJB does not support
multi-threading surprised me. As I said, I wanted my MDB to store incoming
messages in a data structure, and then have threads working on the sending of
messages. How could such a task be achieved by using multiple beans? More
details would be very helpful.
When google-ing, I found somebody commenting that multi-threading would work
when separating the "multi threadedness" into a separate layer outside of the
EJB layer. In such a case, a java job scheduler is needed to handle the
scheduling. Have you or has anybody on the list used any scheduler (such as the
Quartz scheduler)?
Thank you,
Jingwen
---- Original message ----
>Date: Thu, 29 Dec 2005 09:29:03 +0100
>From: Johan Eltes <[EMAIL PROTECTED]>
>Subject: Re: Message-Driven Bean OnMesssage() etc
>To: EJB-INTEREST@JAVA.SUN.COM
>
>You are not allowed to create threads in an EJB.
>One of the reasons is that transaction contexts are bound to threads.
>If you create a thread (most app servers will not let you), that the
>app server will not be able to manage it.
>
>Would it be possible to have multiple MDBs (MDB pool size > 1)
>instead of forking threads within your business logic?
>
>/Johan
>
>29 dec 2005 kl. 06.00 skrev Jingwen Jin:
>
>> I'm writing a pub/sub server that, on receiving an incoming message,
>> stores it into a messageArray, and then creates a thread to forward
>> messages in the array. The following code works ok if the
>> "forwardMessage"
>> method is called within onMessage(); messages get delivered.
>>
>> But whenever I try to deliver the messages in messageArray using a
>> thread
>> as shown below, I get the following exception and messages don't get
>> delivered:
>>
>> ReplyMsgBean.forwardMessage: JMSException:
>> com.sun.messaging.jms.JMSException: [SEND_REPLY(9)] [C4036]: A server
>> error occurred. : transaction failed: Unexpected Broker Exception:
>> [received message with Unknown Transaction ID -1: ignoring message]
>>
>> It looks like the server could not create the connection within the
>> forwardMessage method.
>>
>> I'd appreciate any suggestions.
>>
>> Thanks,
>>
>> Jingwen
>>
>> ---------------------------------
>>
>>
>>
>> public class ReplyMsgBean implements MessageDrivenBean,
>> MessageListener {
>> ...
>> public ReplyMsgBean() throws Exception {
>> messageArray = new ArrayList();
>> mft = new MessageForwardingThread();
>> mft.start();
>> }
>> public void ejbCreate() {
>> try {
>> Context initial = new InitialContext();
>> cf = (ConnectionFactory) initial.lookup(
>> "java:comp/env/jms/MyConnectionFactory");
>> } catch (Exception ex) {
>> logger.severe("ReplyMsgBean.ejbCreate: Exception: " +
>> ex.toString());
>> }
>> }
>> public void onMessage(Message inMessage) {
>> put the message into messageArray
>> }
>> private static void forwardMessage(TextMessage msg) {
>> ...
>> Connection con = cf.createConnection();
>> Session ses = con.createSession(true, 0);
>> producer = ses.createProducer(topic);
>> producer.send(msg);
>> con.close();
>> }
>>
>>
>> final class MessageForwardingThread extends Thread {
>> ...
>> public final void run() {
>> for every-message (msg) in messageArray
>> ReplyMsgBean.forwardMessage(msg);
>>
>> }
>>
>> }
>>
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>>
>
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