Message-driven bean questions

Question

Hello,
i'm an Italian student trying to develop java applications in NetBeans IDE 6.1 with GlassFish V2, using Java EE 5; since I only recently approached java web programming, I have encountered some problems in using enterprise beans, especially message-driven ones: to get in touch with the stuff, I have created an enterprise application project in NetBeans with a plain message-driven bean and a servlet who sends a message to this bean, following an online netbeans tutorial.
I'm using annotations to refer the resource in the servlet (the jms name I assigned the bean is "TestBean"):
@Resource(mappedName="jms/TestBeanFactory")
private ConnectionFactory connectionFactory;
@Resource(mappedName="jms/TestBean")
private Queue queue;I send the message by creating a connection, producing the message with a MessageProducer object, and sending it:
Connection connection = connectionFactory.createConnection();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
MessageProducer messageProducer = session.createProducer(queue);
TextMessage message = session.createTextMessage("This is a message.");
messageProducer.send(message);
messageProducer.close();
connection.close();In the message-driven bean, I have my onMessage() method catching the message and writing to the system.out his text content:
public void onMessage(Message message)
        TextMessage msg = null;
        try
            if (message instanceof TextMessage)
                msg = (TextMessage) message;
                String x = msg.getText();
                System.out.println(x);
        catch (Exception e)
            e.printStackTrace();
            m_ctx.setRollbackOnly();
        catch (Throwable te)
            te.printStackTrace();
    }The message is sent and received, and the content printed. Ok, here are my questions:
1) in the output window of netbeans I see the output but also an exception: "DirectConsumer:Caught Exception delivering messagecom.sun.messaging.jmq.io.Packet cannot be cast to com.sun.messaging.jms.ra.DirectPacket". What does that mean?
2) I can't figure out how to make the bean answer this message to the servlet...and of course the servlet receive this response: in plain words, I would like to send back another message from the bean to the servlet, and process it. Can someone explain me how to do that?
Thanks?

Answer 1

1) in the output window of netbeans I see the output but also an exception: "DirectConsumer:Caught Exception delivering messagecom.sun.messaging.jmq.io.Packet cannot be cast to com.sun.messaging.jms.ra.DirectPacket". What does that mean?casting issue, but i don't know why.
2) I can't figure out how to make the bean answer this message to the servlet...and of course the servlet receive this response: in plain words, I would like to send back another message from the bean to the servlet, and process it. Can someone explain me how to do that?a message driven bean cannot sent a response back. MDB is asynchronous. if you need to send a response back, you
shouldn't be using an MDB. In that case, it sounds like you want a synchronous response. let a SLSB do it.
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