Subscriber.

• By Gopalan Suresh Raj
• July 18, 2000

import javax.jms.*;
import fiorano.jms.rtl.FioranoInitialContext;

class Subscriber implements MessageListener {

  Sender m_nasdaq;

  String m_bourseName; // Name of the Bourse ("nasdaq" or "nyse")
  String m_nasdaqSymbols[]= {"SUNW", "MSFT", "CPWR"};

  double m_buyBelow = 10;  // Buy if prices go below $10
  double m_sellAbove = 90; // Sell if prices go above $90

  int m_buyNumStocks = 1000; // No. of Stocks to buy
  int m_sellNumStocks = 100; // No. of Stocks to sell

  public Subscriber (String bourseName, String customerID) {
    m_nasdaq = new Sender(customerID);
    m_nasdaq.TalkToYourStockBroker ();

    m_bourseName = bourseName;
  }

  public static void SubscribeToStockQuotes (
                           String customerID) {
    try {

      //  1. Create the InitialContext Object used for looking up
      //     JMS administered objects on the Fiorano/EMS
      //     located on the default host.
      

      FioranoInitialContext initialCtx = null;
      initialCtx = new FioranoInitialContext ();
      initialCtx.bind ();



      // 1.1  Lookup Connection Factory and Topic names

      TopicConnectionFactory topicConnFactory =
                (TopicConnectionFactory) initialCtx.lookup
                                           ("primaryTCF");
      Topic nasdaqTopic = (Topic)initialCtx.lookup
                                           ("Nasdaq_Topic");


      // 1.2  Dispose the InitialContext resources

      initialCtx.dispose();


      // 2. create and start a topic connection

      System.out.println("Creating topic connection");
      TopicConnection topicConnection =
                  topicConnFactory.createTopicConnection();
      topicConnection.start ();


      // 3. create topic session on the connection just created

      System.out.println
               ("Creating topic session: not transacted, auto ack");
      TopicSession topicSession =
                         topicConnection.createTopicSession(false, Session.AUTO_ACKNOWLEDGE);


      // 4. create subscriber

      System.out.println("Creating topic, subscriber");
      TopicSubscriber nasdaqTopicSubscriber =
        topicSession.createSubscriber (nasdaqTopic);


// 5. install an asynchronous listener/callback on the subscriber
//    object just created

      System.out.println ("Ready to subscribe for messages :");
      nasdaqTopicSubscriber.setMessageListener
                   (new Subscriber ("nasdaq", customerID));
    }
    catch (Exception e) {
      e.printStackTrace ();
    }

  }

  /**
   *  Message listener which receives messages asynchronously
   *  for the bound subscriber.
   */
  public void onMessage (Message msg) {
    String stockName;
    double price = 0;

    try {

      //  When a message is received, print it out to standard
      //  output & send a Message to Queue to Buy or Sell stock

      MapMessage mapMsg = (MapMessage)msg;
      if (m_bourseName.equals("nasdaq")) {
        for (int i = 0; i < m_nasdaqSymbols.length; i++) {
          price = mapMsg.getDouble(m_nasdaqSymbols[i]);
          System.out.println ("Received : " + m_bourseName+":
                Value of "+ m_nasdaqSymbols[i]+ " = $"+ price);
          if(price < m_buyBelow) {
            m_nasdaq.BuyStocks (m_nasdaqSymbols[i],
                                  m_buyNumStocks, price);
          }
          if(price > m_sellAbove) {
            m_nasdaq.SellStocks (m_nasdaqSymbols[i],
                                    m_sellNumStocks, price);
          }
        }
      }
      System.out.println ("\n");
    }
    catch (JMSException e) {
      e.printStackTrace ();
    }
  }

  public static void main (String args[]) {

    if (args.length <= 0) { 
      printUsageInfo ();
      System.exit (1);
    }

    SubscribeToStockQuotes (args[0]);
  }

  private static void printUsageInfo () {
    System.out.println ("Usage: Subscriber customerID");
    System.out.println
         ("customerID: Name or Account Number of the customer");
  }
}