Following are the main Source files of this application

/*
 * @author Rajat Gupta
 * @version 1.0
 *
 * Name of the Application        : ChatSubscriber.java
 * Development Environment       : Oracle9i JDeveloper

 * Creation/Modification History  :
 *
 *
 *   Rajat Gupta        28-May-2003        Created
 */

package oracle.otnsamples.oc4jjms;

// JMS Imports
import javax.jms.Message;

import javax.jms.Session;
import javax.jms.TextMessage;
import javax.jms.Topic;
import javax.jms.TopicConnection;
import javax.jms.TopicConnectionFactory;
import javax.jms.TopicSession;
import javax.jms.TopicSubscriber;

// Naming Imports
import javax.naming.Context;


/**
 * This class is the object representation of a Chat client. Whenever a new
 * user logs into the application, then this object is first created and
 * assigned to the client.
 *
 */
public class ChatSubscriber  {

  /**
   * TopicConnectionFactory Object
   */
//  private TopicConnectionFactory topicCF;


  /**
   * TopicConnection Object
   */
  private TopicConnection topicConnection;

  /**
   * Topic Session Object
   */
  private TopicSession topicSession;

  /**
   * Topic Object

   */

  private Topic topic;

  /**
   * Receiver Object. The application receives the message from the topic through
   * this object.
   */
  private TopicSubscriber receiver;

  /**
   * Empty constructor
   */
  public ChatSubscriber(){

  }

  /**
   * This method actually registers the chat client with the topic. The
   * method first creates a connection to the topic and then creates a
   * Receiver object to the topic.
   *
   * @param jndiContext JNDI Context form the application
   * @param clientID ID of the Client currently connected
   *
   * @exception Exception In Case the application throws some exception
   */
  public void createSubscriber(Context jndiContext, String clientID)
                                                            throws Exception{


    // Lookup the Topic Connection factory and create the
    // TopicConnectionFactory object
    TopicConnectionFactory topicCF = (TopicConnectionFactory)jndiContext.lookup
          ("jms/ChatTopicConnectionFactory");

    // Create a connection to the topic
    topicConnection = topicCF.createTopicConnection();

    // Set the Client ID (subscriber) for this object
    topicConnection.setClientID(clientID);

    // Create a Session to this topic
    topicSession = topicConnection.createTopicSession
                                         (true, Session.AUTO_ACKNOWLEDGE);

    // Lookup the topic

    topic = (Topic)jndiContext.lookup
                            ("jms/ChatTopic");

    // Create a durable subscriber to the specified topic.
    receiver = topicSession.createDurableSubscriber(topic, "OTN");

    // Close the context
    jndiContext.close();

    // Start the connection to the topic
    topicConnection.start();

    return;
  }

  /**
   * This method connects to the topic and checks if a new message has

   * arrived for the client. If a message is present, then the method
   * dequeues and returns it. If no new message is present for the client
   * then the method returns a null object.
   *
   * @exception Exception In Case the application throws some exception
   *
   * @return Message for the connected client
   */
  public String getMessage() throws Exception{
    String message = null;

    // Receive the message; if any
    Message msg = receiver.receiveNoWait();

    if (msg != null){
      // Extract the Message
      message = ((TextMessage)msg).getText();
    }


    // Return the message
    return message;
  }
}