Reading a message from a Queue and display it to the user?

Question

I want to know first how many messages are already existing in a Queue. The following class Browser will return the number of messages existing in Queue. Now, I want user to enter the number of messages to be read from a queue and display only that number of messages to the client. I do not want to read all the messages from a queue but only those number of messages which user wants to read. Please check the code and reply what should be done.

public class Browser
{
    public static void main(String[] args) throws Exception
    {
    |   // get the initial context
    |   InitialContext ctx = new InitialContext();
    |                                                                      
    |   // lookup the queue object
    |   Queue queue = (Queue) ctx.lookup("queue/queue0");
    |                                                                      
    |   // lookup the queue connection factory
    |   QueueConnectionFactory connFactory = (QueueConnectionFactory) ctx.
    |       lookup("queue/connectionFactory");
    |                                                                      
    |   // create a queue connection
    |   QueueConnection queueConn = connFactory.createQueueConnection();
    |                                                                      
    |   // create a queue session
    |   QueueSession queueSession = queueConn.createQueueSession(false,
    |       Session.AUTO_ACKNOWLEDGE);
    |                                                                      
    |   // create a queue browser
    |   QueueBrowser queueBrowser = queueSession.createBrowser(queue);
    |                                                                      
    |   // start the connection
    |   queueConn.start();
    |                                                                      
    |   // browse the messages
    |   Enumeration e = queueBrowser.getEnumeration();
    |   int numMsgs = 0;
    |                                                                      
    |   // count number of messages
    |   while (e.hasMoreElements()) {
    |   |   Message message = (Message) e.nextElement();
    |   |   numMsgs++;
    |   }
    |                                                                      
    |   System.out.println(queue + " has " + numMsgs + " messages");
    |                                                                      
    |   // close the queue connection
    |   queueConn.close();
    }
}


To read the number of messages as per user's requirements....
String NUMBER = request.getParameter("number"); 
.......
.......
.......
connection.start();
            for (int s = 0; s <= Integer.parseInt(NUMBER); s++){
             while (true){
                Message m = qReceiver.receive();
                if (m != null){
                    if (m instanceof BytesMessage){
                        BytesMessage bytesMessage = (BytesMessage)m;
                        PrintStream buffer = null;
                        for ( int i = 0; i < (int)bytesMessage.getBodyLength(); i++) {
                            buffer.append((char) bytesMessage.readByte());
                            }
                            String msg = buffer.toString().trim();

                            System.out.println("Reading Message: " + msg);
                       }else if (m instanceof TextMessage){
                        TextMessage textMessage = (TextMessage)m;
                        System.out.println("Reading message: " + textMessage.getText());
                    }else {
                        break;
                    }

Answer 1

i assume that you are using a MessageListner, so OnMessage() method will be called once a message comes up. In this method you can keep a counter, once this counter reaches maximum allowed, you can call connection.stop() to stop consuming messages from the queue.

You can always restart by calling connection.start() again.