voter.java

java2高级教程大学教程的配套光盘源码

// Voter.java
// Voter is the GUI that allows the client to vote
// for a programming language. Voter sends the vote
// to the "Votes" queue as a TextMessage.
package com.deitel.advjhtp1.jms.voter;

// Java core packages
import java.awt.*;
import java.awt.event.*;

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

public class Voter extends JFrame {

   private String selectedLanguage;
   
   // JMS variables
   private QueueConnection queueConnection;
   private QueueSession queueSession;
   private QueueSender queueSender;
   
   // Voter constructor
   public Voter()
   {
      // lay out user interface
      super( "Voter" );

      Container container = getContentPane();
      container.setLayout( new BorderLayout() );

      JTextArea voteArea =
         new JTextArea( "Please vote for your\n" +
            "favorite programming language" );
      voteArea.setEditable( false );
      container.add( voteArea, BorderLayout.NORTH );

      JPanel languagesPanel = new JPanel();
      languagesPanel.setLayout( new GridLayout( 0, 1 ) );
      
      // add each language as its own JCheckBox
      // ButtonGroup ensures exactly one language selected
      ButtonGroup languagesGroup = new ButtonGroup();
      CheckBoxHandler checkBoxHandler = new CheckBoxHandler();
      String languages[] = 
         { "C", "C++", "Java", "Lisp", "Python" };
      selectedLanguage = "";
      
      // create JCheckBox for each language
      // and add to ButtonGroup and JPanel
      for ( int i = 0; i < languages.length; i++ ) {
         JCheckBox checkBox = new JCheckBox( languages[ i ] );
         checkBox.addItemListener( checkBoxHandler );
         languagesPanel.add( checkBox );
         languagesGroup.add( checkBox );
      }
      
      container.add( languagesPanel, BorderLayout.CENTER );
      
      // create button to submit vote
      JButton submitButton = new JButton( "Submit vote!" );
      container.add( submitButton, BorderLayout.SOUTH );

      // invoke method submitVote when submitButton clicked
      submitButton.addActionListener (

         new ActionListener() {

            public void actionPerformed ( ActionEvent event ) {
               submitVote();
            }
         }
      );
      
      // invoke method quit when window closed
      addWindowListener(

         new WindowAdapter() {

            public void windowClosing( WindowEvent event ) {
               quit();
            }
         }
      );
      
      // connect to message queue
      try {

         // create JNDI context
         Context jndiContext = new InitialContext();

         // retrieve queue connection factory and
         // queue from JNDI context
         QueueConnectionFactory queueConnectionFactory = 
            ( QueueConnectionFactory )
            jndiContext.lookup( "VOTE_FACTORY" );
         Queue queue = ( Queue ) jndiContext.lookup( "Votes" );

         // create connection, session and sender
         queueConnection = 
            queueConnectionFactory.createQueueConnection();
         queueSession =
            queueConnection.createQueueSession( false,
               Session.AUTO_ACKNOWLEDGE );
         queueSender = queueSession.createSender( queue );
      }

      // process Naming exception from JNDI context
      catch ( NamingException namingException ) {
         namingException.printStackTrace();
         System.exit( 1 );
      }

      // process JMS exception from queue connection or session
      catch ( JMSException jmsException ) {
         jmsException.printStackTrace();
         System.exit( 1 );
      }

   } // end Voter constructor

   // submit selected vote to "Votes" queue as TextMessage
   public void submitVote()
   {
      if ( selectedLanguage != "" ) {	

         // create text message containing selected language
         try {
            TextMessage voteMessage = 
               queueSession.createTextMessage();
            voteMessage.setText( selectedLanguage );

            // send the message to the queue
            queueSender.send( voteMessage );
         }

         // process JMS exception
         catch ( JMSException jmsException ) {
            jmsException.printStackTrace();
         }
      }

   } // end method submitVote

   // close client application
   public void quit()
   {
      if ( queueConnection != null ) {

         // close queue connection if it exists
         try {
            queueConnection.close();
         }

         // process JMS exception
         catch ( JMSException jmsException ) {
            jmsException.printStackTrace();
         }
      }

      System.exit( 0 );

   } // end method quit

   // launch Voter application
   public static void main( String args[] )
   {
      Voter voter = new Voter();
      voter.pack();
      voter.setVisible( true );
   }

   // CheckBoxHandler handles event when checkbox checked
   private class CheckBoxHandler implements ItemListener {

      // checkbox event
      public void itemStateChanged( ItemEvent event )
      {
         // update selectedLanguage
         JCheckBox source = ( JCheckBox ) event.getSource();
         selectedLanguage = source.getText();
      }
   }
}

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