L'observer et l'observable sert à modéliser des vues et de faire des actions communes sur chacune. Anisi, dans le cadre d'un client/serveur, les données qui ont changées par un utilisateur seront apparents pour les autres utilisateurs (notion de rafraîchissement de données). Or le problème, en RMI, c'est que ces deux classes sympathiques ne peuvent pas fonctionner. Ainsi, j'ai fait un petit package util et fonctionnel (utilisation de Publishing et de Subscribing).
Voilà
Source / Exemple :
/*
*
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- /
package observer;
import java.io.Serializable;
import java.rmi.Remote;
import java.rmi.RemoteException;
/**
*
- TODO To change the template for this generated type comment go to
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- /
public interface Subscriber extends Remote, Serializable {
public void update(Object pub, Object code) throws RemoteException;
}
/////////////////////////////////////////////////////////////////////////////////
/*
*
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- /
package observer;
import java.rmi.Remote;
import java.rmi.RemoteException;
/**
*
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- /
public interface Publisher extends Remote {
public void addSubscriber(Subscriber s) throws RemoteException;
public void notifyAllSubscribers()throws RemoteException;
public void removeSubscriber(Subscriber s) throws RemoteException;
public void removeAllSubscribers() throws RemoteException;
}
/////////////////////////////////////////////////////////////////
/*
*
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- /
package observer;
import java.io.Serializable;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.Enumeration;
import java.util.Vector;
/**
*
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- /
public class BasicPublisher extends UnicastRemoteObject implements Publisher, Serializable {
private Vector subscribers;
public BasicPublisher() throws RemoteException {
subscribers = new Vector();
}
public void addSubscriber(Subscriber s) throws RemoteException {
subscribers.addElement(s);
}
public void notifyAllSubscribers() throws RemoteException {
notifySubscribers(null);
}
public void removeSubscriber(Subscriber s) throws RemoteException {
subscribers.removeElement(s);
}
public void removeAllSubscribers() throws RemoteException {
subscribers.removeAllElements();
}
public void notifySubscribers(Object pub, Object code) {
Vector deadSubs = null;
Enumeration e = subscribers.elements();
while (e.hasMoreElements()) {
Subscriber s = (Subscriber) e.nextElement();
try {
s.update(pub, code);
}
catch (java.rmi.ConnectException ce) { //serious
if (deadSubs == null) deadSubs = new Vector();
deadSubs.addElement(s);// must be dead
}
catch (java.rmi.NoSuchObjectException nsoe){ //serious
if (deadSubs == null) deadSubs = new Vector();
deadSubs.addElement(s);// must be dead
}
catch (java.rmi.RemoteException re) {
/*might recover?*/
}
}
if (deadSubs != null) {
e = deadSubs.elements();
while (e.hasMoreElements()) {
Subscriber s = (Subscriber) e.nextElement();
try {
removeSubscriber(s); // forget this subscriber
} catch (RemoteException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
}
}
public void notifySubscribers(Object pub) throws RemoteException {
notifySubscribers(pub, null);
}
}
/////////////////////////////////////////////////////////////////////////
/*
*
- TODO To change the template for this generated file go to
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- /
package observer;
import java.io.Serializable;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
/**
*
- TODO To change the template for this generated type comment go to
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- /
public class Publishing extends UnicastRemoteObject implements Publisher, Serializable {
BasicPublisher pub;
public Publishing() throws RemoteException {
pub = new BasicPublisher();
}
/** Delegate Publisher interface to BasicPublisher */
public void addSubscriber(Subscriber s) throws RemoteException {
pub.addSubscriber(s);
}
public void notifyAllSubscribers() throws RemoteException{
pub.notifyAllSubscribers();
}
public void removeSubscriber(Subscriber s) throws RemoteException{
pub.removeSubscriber(s);
}
public void removeAllSubscribers() throws RemoteException {
pub.removeAllSubscribers();
}
}
////////////////////////////////////////////////////////////////////////
/*
*
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- /
package observer;
import java.lang.reflect.*;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
/**
*
- TODO To change the template for this generated type comment go to
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- /
public class Subscribing extends UnicastRemoteObject implements Subscriber {
//Variables globales
private Method methode;
private Object instance;
private Object[] params;
public Subscribing(Object instance, Method methode, Object[] params) throws RemoteException {
this.instance = instance;
this.methode = methode;
this.params = params;
this.methode.setAccessible(true);
}
/* (non-Javadoc)
- @see dico.observer.Subscriber#update(java.lang.Object, java.lang.Object)
- /
public void update(Object pub, Object code) throws RemoteException {
// TODO Auto-generated method stub
try{
methode.invoke(instance, params);
}
catch(Exception e){
}
}
}
Conclusion :
Enjoy it :D
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