weatherlistener.java

高级java2 大学教程(含源码,经典的Java学习教程

// WeatherListener.java
// WeatherListener is the MessageListener for a subscription
// to the Weather topic. It implements the specified onMessage
// method to update the GUI with the corresponding city's
// weather.
package com.deitel.advjhtp1.jms.weather;

// Java extension packages
import javax.jms.*;
import javax.swing.*;

// Deitel packages
import com.deitel.advjhtp1.rmi.weather.WeatherBean;

public class WeatherListener implements MessageListener {

   private WeatherDisplay weatherDisplay;

   // WeatherListener constructor
   public WeatherListener( WeatherDisplay display )
   {
      weatherDisplay = display;
   }

   // receive new message
   public void onMessage( Message message )
   {
      // retrieve and process message
      try {

         // ensure Message is an ObjectMessage
         if ( message instanceof ObjectMessage ) {
            
            // get WeatherBean from ObjectMessage
            ObjectMessage objectMessage = 
               ( ObjectMessage ) message;
            WeatherBean weatherBean =
               ( WeatherBean ) objectMessage.getObject();
            
            // add WeatherBean to display
            weatherDisplay.addItem( weatherBean );
            
         } // end if

         else {
            System.out.println( "Expected ObjectMessage," +
               " but received " + message.getClass().getName() );
         }
         
      } // end try

      // process JMS exception from message
      catch ( JMSException jmsException ) {
         jmsException.printStackTrace();
      }
      
   } // end method onMessage
}

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