javaRMI/ChatChannel.java at main · daibeal/javaRMI · GitHub

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// CSD 2013, Pablo Galdámez
import java.rmi.*;
import java.rmi.server.*;
import java.util.*;

//
// Simple ChatChannel implementation
//
public class ChatChannel
   extends UnicastRemoteObject
   implements IChatChannel
{
   public static final String LEAVE = "LEAVE";
   public static final String JOIN = "JOIN";

   private String name;
   private Hashtable <String, IChatUser> users = new Hashtable<String, IChatUser> ();

   public ChatChannel (String name) throws RemoteException {
      super (ChatConfiguration.the().getMyPort());
      this.name = name;
   }

   //
   // ISA IChatChannel
   //
   public String getName () throws RemoteException {
      return name;
   }

   //
   // ISA IChatChannel
   //
   public boolean join (IChatUser usr) throws RemoteException
   {
      String nick = usr.getNick();
      String keyNick = nick.trim().toLowerCase();
      if (users.get (keyNick) != null) return false; // User already in channel
      users.put (keyNick, usr);
      notifyUsers (JOIN, nick);
      return true;
   }

   //
   // ISA IChatChannel
   //
   public boolean leave (IChatUser usr) throws RemoteException
   {
      String nick = usr.getNick();
      String keyNick = nick.trim().toLowerCase();
      if (users.get (keyNick) == null) return false; // User not found
      users.remove (keyNick);

      // Channel sends a control message to all users at the channel---> one user left
      notifyUsers (LEAVE, nick);
      return true;
   }

   //
   // ISA IChatChannel
   //
   public void sendMessage (IChatMessage msg) throws RemoteException
   {
      purge ();
      for (IChatUser usr: users.values()) {
	      usr.sendMessage (msg);
      }
   }

   //
   // ISA IChatChannel
   //
   public IChatUser [] listUsers () throws RemoteException {
      purge ();
      return users.values().toArray(new IChatUser[users.size()]);
   }

   //
   // private function to purge stale users
   //
   private void purge (){
      String [] keys = users.keySet().toArray(new String [users.size()]);
      for (int i=0; i<keys.length; i++) {
	 try {
	    users.get (keys[i]).getNick(); // Remote invo to check if stale or alive
	 } catch (Exception e){
	    users.remove (keys[i]); // Remove stale users
	    notifyUsers (LEAVE, keys[i]);   // this notification sends lowercase nicks (keys)
	 }
      }
   }

   //
   // When users leave or join this channel, we send a message to the remaning users, so that
   // they can update their fancy UI's :)
   //
   private void notifyUsers (String code, String nick) {
      IChatMessage msg = null;
      try {
	 msg = new ChatMessage (null, this, code + " " + nick);
      } catch (Exception e) {return;}

      for (IChatUser usr: users.values()) {
	 try {
	    usr.sendMessage (msg);
	 } catch (Exception e) {} // Ignore errors when sending channel notifications
      }

   }

}