FrontlineEventBus.java

package net.frontlinesms.events.impl;

import java.util.concurrent.CopyOnWriteArrayList;

import net.frontlinesms.events.EventBus;
import net.frontlinesms.events.EventObserver;
import net.frontlinesms.events.FrontlineEventNotification;

/**
 * Implementation of the event bus.
 * This class uses CopyOnWriteArrayList, so it
 * is thread safe.
 * @author Dieterich Lawson <dieterich@medic.frontlinesms.com>
 * @author Alex Anderson <alex@frontlinesms.com>
 */
public class FrontlineEventBus implements EventBus{
	
	/** the observers that receive event notifications */
	private CopyOnWriteArrayList<EventObserver> observers;
	
	public FrontlineEventBus(){
		observers = new CopyOnWriteArrayList<EventObserver>();
	}
	 
	/** @see net.frontlinesms.events.EventBus#registerObserver(net.frontlinesms.events.EventObserver) */
	public void registerObserver(EventObserver observer){
		observers.addIfAbsent(observer);
	}
	

	/** @see net.frontlinesms.events.EventBus#unregisterObserver(net.frontlinesms.events.EventObserver) */
	public void unregisterObserver(EventObserver observer){
		observers.remove(observer);
	}

	/** @see net.frontlinesms.events.EventBus#triggerEvent(net.frontlinesms.events.FrontlineEvent) */
	public void notifyObservers(FrontlineEventNotification event){
		for(EventObserver observer: observers){
			observer.notify(event);
		}
	}
}