Server Implementation

Listing 11.2 RemoteServerImpl.java (Complete code)

import java.rmi.*;
import java.rmi.server.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.border.*;
import java.util.*;

//server class
public class RemoteServerImpl extends 
	UnicastRemoteObject 
	implements ServerInterface {

  //instance variables
  private JButton btnSend;
  private JTextArea txtReceive,txtPass;
  private ClientInterface client;

  //vector used to store messages
  private Vector messages = new Vector();
  private ThreadHandler run;

  //constructor
  public RemoteServerImpl()
	throws RemoteException{

	System.out.println("Creating remote object"); 
	this.setup();
	this.bindIt();
	this.startThread(); 
  }

  //{{Method block}}//
  //method to create various components
  private void setup(){

	//create a frame
	JFrame frame = new JFrame("Remote Server"); 	 

	//get the content pane object
	Container cp = frame.getContentPane();
	
	//panel for buttons
	JPanel btnPanel = new JPanel();
	
	//text area for messages received.
	txtReceive = new JTextArea(15,45);
	
	//set the border of text area
	txtReceive.setBorder(BorderFactory.createTitledBorder(
	"Messages Received"));
	txtReceive.setEditable(false);

	//text area for typing messages.
	txtPass = new JTextArea(5,45);
	txtPass.setBorder(BorderFactory.createTitledBorder(
	"Type your message here"));

	//button used to send a message
	btnSend = new JButton("Send Message");
	btnSend.addActionListener(new ButtonHandler());
	
	JScrollPane 
	 cPane = new JScrollPane(txtReceive),
	 sPane = new JScrollPane(txtPass);

	//add all the components 
	btnPanel.add(btnSend);
	cp.add(cPane,BorderLayout.NORTH);
	cp.add(sPane,BorderLayout.CENTER);
	cp.add(btnPanel,BorderLayout.SOUTH);

	//set default close operation
	frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

	//pack the frame and show it
	frame.pack();
	frame.show();
	
	//set focus
	txtPass.requestFocus();
  }

  //method used to bind the server
  private void bindIt(){
	try{
	 Naming.rebind("Server",this);
	 }catch(Exception ex){
	   txtReceive.append(ex.getMessage());
	 }
  }
	
  //method used to register the client. It gets a reference
  //to the remote client that is used to identify the client.
  public String getRegistered(ClientInterface ci)
	throws RemoteException{
		
	client = ci;
	txtReceive.append("Registered a remote client");
	return "Registered";
   }

  //remote method used to post a message to the
  //server.
  public void passMessage(String message)
	throws RemoteException {
	txtReceive.append(message);
  }

  //method used to start the thread
  private void startThread(){
	messages = new Vector();
	run = new ThreadHandler();
	Thread th = new Thread(run);
	th.start();
}

  //main method creates an instance of the 
  //remote object implementation class
  public static void main(String args[]){
	
    try{
	 RemoteServerImpl obj = new RemoteServerImpl();
       }catch(Exception ex){
	  System.out.println(ex.getMessage());
       } 
}

//{{Private classes}}///
  //event handling class.
  private class ButtonHandler 
	implements ActionListener{

	//method invoked when the button is pressed
	 public void actionPerformed(ActionEvent ae){
	 
	   //add the message to vector
	   messages.add(txtPass.getText());
	   txtPass.setText("");
 	   txtPass.requestFocus();
	 
	   //method used to notify the waiting thread
 	   run.wakeUp(); 
	}
  }

// Class used to handle threading 
private class ThreadHandler 
	implements Runnable {
	
	//method used to notify the waiting thread
	public synchronized void wakeUp(){
	 	notifyAll();
		
	}

	//method used to pass messages to remote client
	public synchronized void submit()
	 	throws Exception{ 	 		
	   if(messages.size()<1){

		//no data available please wait
		wait();
	    }
	    else{
		 try{
		 for(int i=0;i<messages.size();i++){
	 	 client.passMessage("\n" + messages.elementAt(0));
	 	 messages.removeElementAt(0);
	           }
		 }catch(Exception ex){
	 	 	wait();
	      }
	  }
      }
	
	public void run(){
	 while(true){	
		try{
		    submit();
		  }catch(Exception ex){
		    txtReceive.append(ex.getMessage());
		  } 
	   }
	}
     }
}