Client Implementation

Listing 4.3 GreaterClient.java (Complete code)

import javax.swing.*;
import java.rmi.*;
import java.awt.*;
import java.awt.event.*;

// Client implementation
public class GreaterClient 
	extends JFrame{
	
  //instance variables
  private JTextField txtOne,txtTwo;
  private JTextArea txtMessage;
  private JLabel lblOne,lblTwo;
  private JButton btnCompare;
  private GreaterInterface obj;
	
  //constructor
  public GreaterClient(){
				
    super("GreaterClient");
	 
    //calling method to create components
    this.createComponents();
    
    //method to get a remote reference
    this.connect();
    
    //setting the default close operation
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Causes this Window to be sized to fit the 
    //preferred size and layouts of its subcomponents. 
    pack();
   
    //shows the window
    show();
}
	
//method to create various components
private void createComponents(){
    Container cp = getContentPane();
		
    //panels for buttons, textfields. 
    JPanel 
      topPanel = new JPanel(new GridLayout(2,2)),
      centerPanel= new JPanel(new BorderLayout()),
      btnPanel = new JPanel(new GridLayout(1,1));

   //text fields for entering numbers
   txtOne = new JTextField(5);
   txtTwo = new JTextField(5);
   lblOne = new JLabel("First Number");
   lblTwo = new JLabel("Second Number");


   //text area used to show message
   txtMessage = new JTextArea(7,25);


   //button used to call remote method
   btnCompare = new JButton("Compare");
   
   //add an ActionListener to the button.
   btnCompare.addActionListener(new ButtonHandler());
  
   //add the components
   topPanel.add(lblOne);topPanel.add(txtOne);
   topPanel.add(lblTwo);topPanel.add(txtTwo);
   centerPanel.add(txtMessage);
   btnPanel.add(btnCompare);
   cp.add(topPanel,BorderLayout.NORTH);
   cp.add(centerPanel);
   cp.add(btnPanel,BorderLayout.SOUTH);
}

//method used to connect to the server
private void connect(){
   try{
        obj = (GreaterInterface)Naming.lookup("Server");
     }catch(Exception ex){
         txtMessage.setText(ex.getMessage());
     }
}

//main method
 public static void main(String args[]){
        new GreaterClient();
} 	

//Event handling class
private class ButtonHandler 
    implements ActionListener{
    
     public void actionPerformed(ActionEvent ae){
	try{

	   //get the value of first text field
	   int one = Integer.parseInt(txtOne.getText());
	  
	   //get the value of second text field
	   int two = Integer.parseInt(txtTwo.getText());
	 	 
	   //calling the remote method
	   String msg = obj.getGreater(one,two);	
	 
 	  //shows the value returned by the method
	  txtMessage.setText(msg);
	 }catch(Exception ex){
	   txtMessage.setText("Error: " +ex.getMessage());
	 }
    }
  }
}