import java.rmi.*;
import java.rmi.server.*;
import java.rmi.registry.*;
import java.applet.Applet;

interface xWatch extends java.rmi.Remote
{
   public int getClientId() throws java.rmi.RemoteException;
   public boolean removeClientId(int id) throws java.rmi.RemoteException;
   // all additional remote methods here!!!
}

interface xNotify extends java.rmi.Remote
{
}

class xClient extends Applet implements xNotify 
{
   private int connectionId = -1;
   private xWatch servlet = null;
   private String registryName = null;
   public void init()
   {
		try {
         UnicastRemoteObject.exportObject( this );
			// get the host name where the applet was loaded
         String host = "";
         if (! (host = getCodeBase().getHost()).equals("") ) 
         {
            host = "localhost";
         }
            
			registryName = "rmi://" + getCodeBase().getHost() + ":1099/";

			// append the name of the remote object within the registry
			registryName += "xRMI";

			// obtain a reference to the remote object
			System.out.println("obtain remote object reference for " + registryName );
	      servlet = (xWatch)Naming.lookup(registryName);
	      if (servlet == null ) {
	         System.err.println("Failed to bind to remote object.");
	      }
		} catch (Exception e) {
			dbg("Cannot connect to RMI registry for jdbcrmi");
			return;
		}

		try {
	      if (servlet == null ) {
	         System.err.println("Failed to bind to remote object.");
	      }
			connectionId = servlet.getClientId();
			if (connectionId == -1) {
				dbg("Cannot open database connection.");
			}
         else {
            dbg("connected as id " + connectionId );
         }
	      if (servlet == null ) {
	         System.err.println("connectionId:" + connectionId);
	      }
         
		} catch (Exception ex) {
			dbg("Cannot open  connection.");
		}
	}

	public void finalize() {
		try {
			servlet.removeClientId(connectionId);
		} catch (Exception ex) {}
		super.destroy();
	}

  private void dbg(String str) {
    System.out.println( str );
  }

}


class xImpl extends UnicastRemoteObject implements java.rmi.Remote, xWatch, xNotify
{
   private xService [] service = new xService[5];

   public int getClientId() throws java.rmi.RemoteException
   {
		int connectionId;
		// Loop through connection table until an empty slot is found
		for (connectionId = 0; connectionId < service.length; connectionId++) {
			if (service [connectionId] == null)
				break;
		}
		// If no empty slots found, generate an error
		if (connectionId >= service.length) {
			System.out.println("Out of connection objects.");
			return -1;
		}
		// Create a connection for the new process and run it
		service[connectionId] = new xService(connectionId,this);
		// return the connection identifier
		return connectionId;
   }

   public boolean removeClientId(int id) throws java.rmi.RemoteException
   {
     try {
	   	service[id] = null;
	   } catch (Exception e) {
	      e.printStackTrace();
         return false;
	   }
      return true;
   }
}

class xService 
{
   private int id = -1;
   private xNotify xn = null;

   public xService(int id, xNotify xn)
   {
      this.id = id;
      this.xn = xn;
   }
}

class xStart 
{
   public static void main(String [] args) 
   {
		System.out.println("Starting xRMI...");
		// Create and install the security manager
		System.setSecurityManager(new RMISecurityManager());
		try {
			xImpl servlet = new xImpl ();
			System.out.println("Binding to the registry");
         Naming.rebind("xrmi", servlet);
         //Naming.bind("xrmi", servlet);
			System.out.println("xRMI is started.");
		} catch (Exception e) {
			System.out.println("xImpl.main: an exception occurred: " +
            e.getMessage());
			e.printStackTrace();
		}
      
   }
}