import javax.jms.*;
import javax.naming.*;
import java.util.*;


public class MessageProducer {
    //We would like to keep a reference of TopicConnection,Session
    //and TopicPublisher so that we can destroy it at the end.
    private TopicConnection topicConnection = null;
    private TopicPublisher topicPublisher = null;
    private TopicSession topicSession = null;

    //Names of machines over the network.
    //These machines will have JMS Providers running.
    //In real applications,names of machines should come
    //from the GUI.
    private final String COMPUTER1 = "computer6 ";
    private final String COMPUTER2 = "computer13 ";
    private final String COMPUTER3 = "computer14 ";
    private final String COMPUTER4 = "computer15 ";

    //Connect to the JMS Provider and send the message.
    public String connectToProvider(String topicName, String jmsProvider, 
                                    String msg) {
        //We will get a reference of System properties.
        //We will add the Properties related to JMS functionality.
        Properties env = System.getProperties();
        env.put("com.sun.jms.internal.java.naming.factory.initial", 
                "com.sun.enterprise.naming.SerialInitContextFactory");


        //Port number where the Naming service of
        //remote JMS Provider is listening.
        env.put("rg.omg.CORBA.ORBInitialPort ", "1050 ");

        try {
            //Set the network address of target machine
            //where JMS Provider is running.
            if (jmsProvider.equals("Server1 ")) {
                env.put("org.omg.CORBA.ORBInitialHost", COMPUTER1);
            } else if (jmsProvider.equals("Server2")) {
                env.put("org.omg.CORBA.ORBInitialHost", COMPUTER2);
            } else if (jmsProvider.equals("Server3")) {
                env.put("org.omg.CORBA.ORBInitialHost", COMPUTER3);
            } else if (jmsProvider.equals("Server4")) {
                env.put("org.omg.CORBA.ORBInitialHost", COMPUTER4);
            }

            //Get an object of JNDI InitialContext
            //from given JMS Provider
            Context jndiContext = new InitialContext(env);

            //Get JMS Administrator Objects
            TopicConnectionFactory topicConnectionFactory = 
                    (TopicConnectionFactory) jndiContext.lookup(
                            "TopicConnectionFactory");
            Topic topic = (Topic) jndiContext.lookup(topicName);


            //Establish TopicConnection and TopicSession.
            topicConnection = topicConnectionFactory.createTopicConnection();
            topicSession = topicConnection.createTopicSession(false, 
                                                              Session.AUTO_ACKNOWLEDGE);


            //Create the publisher for the topic of interest.
            topicPublisher = topicSession.createPublisher(topic);

            //Create Message Object and set the text.
            TextMessage message = topicSession.createTextMessage();
            message.setText(msg);


            //We are all set,Send message.
            topicPublisher.publish(message);
        } catch (JMSException e) {
            String err = new String("Exception occurred: " + e.toString());

            return err;
        } catch (NamingException e) {
            String err = new String("Error in JNDI context= " + e.toString());

            return err;
        } finally {
            if (topicConnection != null) {
                try {
                    topicPublisher.close();
                    topicSession.close();
                    topicConnection.close();
                } catch (JMSException e) {
                    return "Connection Closing Exception: " + e.toString();
                }
            } //if
        } //finally

        return "Message Sent Successfully";
    } //connectToProvider()
} //end MessageProducer Class