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jms queue fetching of message as and when it is posted in asynchronous communication

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posted 14 years ago

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i want to know how to fetch a message from a jms queue when it is posted in asynchronous communication between sender and receiver.

ie how to fetch message by using receive method of messageConusmer.

Samanthi perera

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posted 14 years ago

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before fetch you must send messages
this Servlet shows how to send messages

package aop;

import java.io.IOException;
import java.io.PrintWriter;
import javax.jms.ConnectionFactory;
import javax.jms.MessageProducer;
import javax.jms.Queue;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class sendMessage extends HttpServlet {

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {

response.setContentType("text/html;charset=UTF-8");
            //PrintWriter out = response.getWriter();
           
            try {
                Context ctx = new InitialContext();
                ConnectionFactory connectionFactory = (ConnectionFactory) ctx.lookup("jms/tConnectionFactory");
                Queue queue = (Queue) ctx.lookup("jms/tQueue");
                javax.jms.Connection connection = connectionFactory.createConnection();
                javax.jms.Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
                MessageProducer messageProducer = session.createProducer(queue);
                TextMessage message = session.createTextMessage();
                message.setText(request.getParameter("message"));
                System.out.println("It come from Servlet:" + message.getText());
                messageProducer.send(message);

//message sent , it was all

//show what we have done in this servlet
                out.println("<html>");
                out.println("<head>");
                out.println("<title>Servlet sendMessage</title>");
                out.println("</head>");
                out.println("<body>");
                out.println("<center>");
                out.print("Servlet Send this message <h2>" + request.getParameter("message") + "</h2>  to this Queue : <h2>" + queue.getQueueName() + "</h2>");
                out.println("</center>");
                out.println("</body>");
                out.println("</html>");

} catch (Exception ex) {
                ex.printStackTrace();
            }

out.close();

} finally {
            out.close();
        }
    }

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
     * Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

/** 
     * Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

/** 
     * Returns a short description of the servlet.
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}

the this Message Driven Bean shows how to fetch

package mdbs;

import javax.ejb.ActivationConfigProperty;
import javax.ejb.MessageDriven;
import javax.ejb.MessageDrivenContext;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.TextMessage;

@MessageDriven(mappedName = "jms/tQueue", activationConfig = {
    @ActivationConfigProperty(propertyName = "acknowledgeMode", propertyValue = "Auto-acknowledge"),
    @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue")
})
public class TMDBBean implements MessageListener {

public TMDBBean() {
    }
    private MessageDrivenContext mdc;

public void onMessage(Message message) {

TextMessage msg = null;
        try {
            if (message instanceof TextMessage) {
                msg = (TextMessage) message;
                System.out.println("A Message received in TMDB: " +
                        msg.getText());
            } else {
                System.out.println("Message of wrong type: " +
                        message.getClass().getName());

}
        } catch (JMSException e) {
            e.printStackTrace();
            mdc.setRollbackOnly();
        } catch (Throwable te) {
            te.printStackTrace();
        }

}
}

i think you should follow this tutorials is better.

http://weblogs.java.net/blog/kalali/archive/2006/05/step_by_step_to.html
it gives step by step examples.
anyway it is bit old tutorials.But no problem.

Ralph Jaus

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posted 14 years ago

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Hi Anish,

an example for using MesageConsumer.receive() is provided by the following code excerpt: Hope this helps.

SCJP 5 (98%) - SCBCD 5 (98%)

ramprasad madathil

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Posts: 489

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posted 14 years ago

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Besides the code posted, there is an important paradigm to understand.

A 'receive' will deliver the next message in the destination. So if there are say 'n' messages, you have to wrap the call to receive in a loop. And finally when there is no message in the queue, this will block till the next message arrives. You can of course chose to specify a timeout value after which the receive returns.

If that is not desirable, you can instead make a call to receiveNoWait() which returns null if there is no more messages to be read. By checking for the return value, you can exit the loop.

To receive the message again after a time interval, it is necessary to invoke receive() again.

A MessageListener on the other hand receives messages continously from the destination. The 'looping' is done internally the jms runtime on the client.

ram.

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