observer.java

real-time design patterns in Real-time java

package designPatterns.Observer;

import designPatterns.*;
import java.util.LinkedList;
import java.util.Iterator;

import javax.realtime.LTMemory;

public abstract class Observer {

	/*
	 * Observed data
	 */
	protected Data data;
	
	// Clients list
	private LinkedList clientsList;
	
	// Logic of notify method encapsulated into a scoped class 
	ScopedNotify sNotify;

	public Observer(Data data) {
		this.data = data;
		clientsList = new LinkedList();
		sNotify = new ScopedNotify(clientsList, this.data);
	}
	
	public void subscribe(ObserverClient client) {
		clientsList.addLast(client);
	}
	
	public void unsubscribe(ObserverClient client) {
		clientsList.remove(client);
	}

	private LTMemory mem = new LTMemory(1024*16);	

	static class ScopedNotify implements Runnable {
		private LinkedList clients;
		private Data data;
		public ScopedNotify(LinkedList clients, Data data) {
			this.clients = clients;
			this.data = data;
		}
		public void run() {
			Iterator i = clients.iterator();
			while (i.hasNext()) {
				ObserverClient cl = (ObserverClient)i.next();
				cl.accept(data);
			}
		}
	}

	protected void notifyClients() {
		mem.enter(sNotify);
	}
	
	public void acceptData(Data data) {
		this.data.copyValue(data);
		notifyClients();
	}
}