• LoginRoster: our remote interface

/*
 * LoginRoster.java
 *
 * Created on May 8, 2003, 12:48 PM
 */

package chat;

import java.rmi.*;
import java.util.Vector;

/** Remote interface.
 *
 * @author default
 * @version 1.0
 */
public interface LoginRoster extends java.rmi.Remote {
 

    public void login(String user) throws RemoteException;
 
    public void logout(String user) throws RemoteException;
 
    public Vector getLoggedIn() throws RemoteException;
 
}
 
 

• LoginRosterImpl: The server side implementation of our interface.

/*
 * LoginRoster_Impl.java
 *
 * Created on May 8, 2003, 12:51 PM
 */

package chat;

import java.rmi.*;
import java.rmi.server.*;
import java.rmi.registry.*;
import java.net.MalformedURLException;
import java.util.Vector;

/** Unicast remote object implementing LoginRoster_ interface.
 *
 * @author default
 * @version 1.0
 */
public class LoginRoster_Impl extends UnicastRemoteObject implements LoginRoster {

    Vector loggedIn = new Vector();
 
    /** Constructs LoginRoster_Impl object and exports it on default port.
     */
    public LoginRoster_Impl() throws RemoteException {
        super();
    }

    /** Constructs LoginRoster_Impl object and exports it on specified port.
     * @param port The port for exporting
     */
    public LoginRoster_Impl(int port) throws RemoteException {
        super(port);
    }

    /** Register LoginRoster_Impl object with the RMI registry.
     * @param name - name identifying the service in the RMI registry
     * @param create - create local registry if necessary
     * @throw RemoteException if cannot be exported or bound to RMI registry
     * @throw MalformedURLException if name cannot be used to construct a valid URL
     * @throw IllegalArgumentException if null passed as name
     */
    public static void registerToRegistry(String name, Remote obj, boolean create) throws RemoteException, MalformedURLException{

        if (name == null) throw new IllegalArgumentException("registration name can not be null");

        try {
            Naming.rebind(name, obj);
        } catch (RemoteException ex){
            if (create) {
                Registry r = LocateRegistry.createRegistry(Registry.REGISTRY_PORT);
                r.rebind(name, obj);
            } else throw ex;
        }
    }

    /** Main method.
     */
    public static void main(String[] args) {
        System.setSecurityManager(new RMISecurityManager());

        try {
            LoginRoster_Impl obj = new LoginRoster_Impl();
            registerToRegistry("LoginRoster_Impl", obj, true);
        } catch (RemoteException ex) {
            ex.printStackTrace();
        } catch (MalformedURLException ex) {
            ex.printStackTrace();
        }
    }
 
    public void logout(String user) throws RemoteException {
        System.out.println("Logged out " + user);
        loggedIn.remove(user);
    }
 
    public void login(String user) throws RemoteException {
        System.out.println("Logged in " + user);
        loggedIn.add(user);
    }
 
    public Vector getLoggedIn() throws RemoteException {
        System.out.println("Returning logged in vector.  size: " + loggedIn.size());
        return loggedIn;
    }
 
}
 
 

• Chat with new method to get LoginRoster:

package chat;

import java.rmi.*;

/** Remote interface.
 *
 * @author default
 * @version 1.0
 */
public interface Chat extends java.rmi.Remote {

    public void login (String user, String password) throws RemoteException;
 
    public void sendMessage (String message, String user) throws RemoteException;
 
    public void sendMessage (Message message) throws RemoteException;
 
    public LoginRoster getLoginRoster() throws RemoteException;

}
 

• Altered ChatForm

package chat;

import java.rmi.*;
import java.rmi.registry.*;

import javax.swing.JOptionPane;
import java.util.Vector;

/**
 *
 * @author  default
 */
public class ChatForm extends javax.swing.JFrame {

    // Globally visible reference to the stub via interface.
    Chat chat;
    LoginRoster roster;
    String user;
 
    /** Creates new form ChatForm */
    public ChatForm() {
 
        initComponents();
 
        // Get the stub. 
        // Change the URL if connecting to a different machine.
        try {
            System.out.println("Getting chat.");
            chat = (Chat)Naming.lookup("rmi://localhost/ChatImpl");
            System.out.println("Getting roster.");
            roster = chat.getLoginRoster();
        } catch (Exception e) {
            System.out.println("Exception while attempting to lookup ChatImpl.  Message: " + e.getMessage());
            e.printStackTrace();
        }
 
 
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    private void initComponents() {
        jLabel1 = new javax.swing.JLabel();
        jPanel1 = new javax.swing.JPanel();
        btnSend = new javax.swing.JButton();
        btnShowUsers = new javax.swing.JButton();
        btnLogin = new javax.swing.JButton();
        btnLogout = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        txtMessage = new javax.swing.JTextArea();
 
        addWindowListener(new java.awt.event.WindowAdapter() {
            public void windowClosing(java.awt.event.WindowEvent evt) {
                exitForm(evt);
            }
        });
 
        jLabel1.setText("Send a Message to the Bulletin Board");
        getContentPane().add(jLabel1, java.awt.BorderLayout.NORTH);
 
        btnSend.setText("Send");
        btnSend.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnSendActionPerformed(evt);
            }
        });
 
        jPanel1.add(btnSend);
 
        btnShowUsers.setText("Show Users");
        btnShowUsers.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnShowUsersActionPerformed(evt);
            }
        });
 
        jPanel1.add(btnShowUsers);
 
        btnLogin.setText("Login");
        btnLogin.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnLoginActionPerformed(evt);
            }
        });
 
        jPanel1.add(btnLogin);
 
        btnLogout.setText("Logout");
        btnLogout.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnLogoutActionPerformed(evt);
            }
        });
 
        jPanel1.add(btnLogout);
 
        getContentPane().add(jPanel1, java.awt.BorderLayout.SOUTH);
 
        txtMessage.setRows(4);
        jScrollPane1.setViewportView(txtMessage);
 
        getContentPane().add(jScrollPane1, java.awt.BorderLayout.CENTER);
 
        pack();
    }

    private void btnLogoutActionPerformed(java.awt.event.ActionEvent evt) {
        // Add your handling code here:
        try {
            roster.logout(user);
        } catch (Exception e) {
            System.out.println("Exception while attempting to logout.  Message: " + e.getMessage());
            e.printStackTrace();
        }
    }

    private void btnLoginActionPerformed(java.awt.event.ActionEvent evt) {
        try {
            // Add your handling code here:
            System.out.println("Prompting for login.");
            user = JOptionPane.showInputDialog("Enter your username.");
            System.out.println("Logging in.");
            roster.login(user);
            System.out.println("Returning.");
        } catch (Exception e) {
            System.out.println("Exception while attempting to login.  Message: " + e.getMessage());
            e.printStackTrace();
        }

    }

    private void btnShowUsersActionPerformed(java.awt.event.ActionEvent evt) {
        // Add your handling code here:
        try {
            Vector users = roster.getLoggedIn();
            StringBuffer sb = new StringBuffer();
            for (int i =0 ; i < users.size(); i++) {
                sb.append((String) users.get(i));
            }
            JOptionPane.showMessageDialog(this, sb.toString());
        } catch (RemoteException e) {
            System.out.println("RemoteException caught in Show Users.  Message: " + e.getMessage());
            e.printStackTrace();
        }
 
    }

    private void btnSendActionPerformed(java.awt.event.ActionEvent evt) {
        // Send a message to the bulletin board.
        try {
            // Make a message.  Hardcode some thing in until we prompt the user for this information.
            Message message = new Message(txtMessage.getText(), "BulletinBoard", user);
            // chat.sendMessage(txtMessage.getText(), "BulletinBoard");
            chat.sendMessage(message);
        } catch (Exception e) {
            System.out.println("RemoteException while attempting to send message to Bulletin Board.  Message: " + e.getMessage());
        }
 
 
    }

    /** Exit the Application */
    private void exitForm(java.awt.event.WindowEvent evt) {
        System.exit(0);
    }

    /**
    * @param args the command line arguments
    */
    public static void main(String args[]) {
 
        // Set the security policy and security manager.
        System.setProperty("java.security.policy", "client.policy");
        System.setSecurityManager(new RMISecurityManager());
 
        new ChatForm().show();
    }
 

    // Variables declaration - do not modify
    private javax.swing.JLabel jLabel1;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JButton btnSend;
    private javax.swing.JButton btnShowUsers;
    private javax.swing.JButton btnLogin;
    private javax.swing.JButton btnLogout;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea txtMessage;
    // End of variables declaration

}
 

• Altered ChatImpl

package chat;

/*
 * ChatImpl.java
 *
 * Created on April 28, 2003, 11:48 PM
 */

import java.rmi.*;
import java.rmi.server.*;
import java.rmi.registry.*;
import java.net.MalformedURLException;

/** Unicast remote object implementing Chat interface.
 *
 * @author default
 * @version 1.0
 */
public class ChatImpl extends java.rmi.server.UnicastRemoteObject implements Chat {

    BulletinBoard board;
    LoginRoster_Impl roster;
 
    /** Constructs ChatImpl object and exports it on default port.
     */
    public ChatImpl() throws RemoteException {
        super();
        // Fire up our JFrame here.
        board = new BulletinBoard();
        board.show();
        roster = new LoginRoster_Impl();
    }

    /** Constructs ChatImpl object and exports it on specified port.
     * @param port The port for exporting
     */
    public ChatImpl(int port) throws RemoteException {
        super(port);
    }

    /** Register ChatImpl object with the RMI registry.
     * @param name - name identifying the service in the RMI registry
     * @param create - create local registry if necessary
     * @throw RemoteException if cannot be exported or bound to RMI registry
     * @throw MalformedURLException if name cannot be used to construct a valid URL
     * @throw IllegalArgumentException if null passed as name
     */
    public static void registerToRegistry(String name, Remote obj, boolean create) throws RemoteException, MalformedURLException{

        if (name == null) throw new IllegalArgumentException("registration name can not be null");

        try {
            Naming.rebind(name, obj);
        } catch (RemoteException ex){
            if (create) {
                Registry r = LocateRegistry.createRegistry(Registry.REGISTRY_PORT);
                r.rebind(name, obj);
            } else throw ex;
        }
    }

    /** Main method.
     */
    public static void main(String[] args) {
        System.setSecurityManager(new RMISecurityManager());

        try {
            ChatImpl obj = new ChatImpl();
            registerToRegistry("ChatImpl", obj, true);
        } catch (RemoteException ex) {
            ex.printStackTrace();
        } catch (MalformedURLException ex) {
            ex.printStackTrace();
        }
    }
 
     /** deprecated */
   public void login(String user, String password) {
        // roster.login(user);
    }

    /**
      return a reference to the roster.
     */

    public LoginRoster getLoginRoster() throws RemoteException {
        return roster;
    }
 
    public void sendMessage(String message, String user) {
        System.out.println("Message: " + message + " User: " + user);
        // call method on JFrame to add this to our list.
        board.addMessage(message);
    }
 
    /** For sake of time, just make a convenience method to the existing sendMessage method. */
    public void sendMessage(Message message) {
        sendMessage(message.getMessage(), message.getUser());
    }
}

 Try it out!