rmilistclientimpl.java

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/*
 * Java Network Programming, Second Edition
 * Merlin Hughes, Michael Shoffner, Derek Hamner
 * Manning Publications Company; ISBN 188477749X
 *
 * http://nitric.com/jnp/
 *
 * Copyright (c) 1997-1999 Merlin Hughes, Michael Shoffner, Derek Hamner;
 * all rights reserved; see license.txt for details.
 */

import java.rmi.*;
import java.util.*;
import java.rmi.server.*;
import java.rmi.registry.*;

public class RMIListClientImpl implements DistributedList {
  protected String host, service;
  protected int port;

  public RMIListClientImpl (String host, int port, String service) {
    this.host = host;
    this.port = port;
    this.service = service;
  }

  protected IDList idList;
  protected RMIListClient myself;
  protected RMIListServer listServer;
  
  public synchronized void start () throws RemoteException, NotBoundException {
    if (listServer == null) {
      myself = (RMIListClient)
        UnicastRemoteObject.exportObject (new Callback ());
      Registry registry = LocateRegistry.getRegistry (host, port);
      listServer = (RMIListServer) registry.lookup (service);
      try {
        idList = listServer.register (myself);
      } catch (RemoteException ex) {
        listServer = null;
        throw ex;
      }
      fireChangeEvent (new ChangeEvent (this));
    }
  }

  public synchronized void stop () throws RemoteException {
    try {
      if (listServer != null)
        listServer.deregister (myself);
    } finally {
      listServer = null;
      UnicastRemoteObject.unexportObject (myself, true);
    }
  }

  public synchronized void addElement (Object element) {
    if (listServer != null) {
      try {
        listServer.addElement (element);
      } catch (RemoteException ex) {
        listServer = null;
      }
    }
  }

  public synchronized void updateElement (Object oldElement, Object newElement) {
    if (listServer != null) {
      ID id = idList.getID (oldElement);
      if (id != null) {
        try {
          listServer.updateElement (id, newElement);
        } catch (RemoteException ex) {
          listServer = null;
        }
      }
    }
  }

  public synchronized void replaceElement (Object oldElement, Object newElement) {
    if (listServer != null) {
      ID id = idList.getID (oldElement);
      if (id != null) {
        try {
          listServer.replaceElement (id, newElement);
        } catch (RemoteException ex) {
          listServer = null;
        }
      }
    }
  }

  public synchronized void removeElement (Object element) {
    if (listServer != null) {
      ID id = idList.getID (element);
      if (id != null) {
        try {
          listServer.removeElement (id);
        } catch (RemoteException ex) {
          listServer = null;
        }
      }
    }
  }

  public Enumeration getElements () {
    return idList.getElements ();
  }

  protected Vector listeners = new Vector ();

  public void addChangeListener (ChangeListener listener) {
    listeners.addElement (listener);
  }

  public void removeChangeListener (ChangeListener listener) {
    listeners.removeElement (listener);
  }

  protected void fireChangeEvent (ChangeEvent changeEvent) {
    synchronized (listeners) {
      for (int i = 0; i < listeners.size (); ++ i)
        ((ChangeListener) listeners.elementAt (i)).changeOccurred (changeEvent);
    }
  }

  class Callback implements RMIListClient {
    public void elementAdded (ID id, Object element) {
      idList.addElement (id, element);
      fireChangeEvent (new ChangeEvent (RMIListClientImpl.this));
    }
    
    public void elementUpdated (ID oldID, ID id, Object element) {
      idList.updateElement (oldID, id, element);
      fireChangeEvent (new ChangeEvent (RMIListClientImpl.this));
    }
    
    public void elementReplaced (ID oldID, ID id, Object element) {
      idList.replaceElement (oldID, id, element);
      fireChangeEvent (new ChangeEvent (RMIListClientImpl.this));
    }
    
    public void elementRemoved (ID id) {
      idList.removeElement (id);
      fireChangeEvent (new ChangeEvent (RMIListClientImpl.this));
    }
  }
}