[jboss-user] [JBoss AOP] - Re: The reuse&&JBoss AOP

Flavia Rainone do-not-reply at jboss.com
Thu Feb 3 12:27:06 EST 2011

Flavia Rainone [http://community.jboss.org/people/flavia.rainone%40jboss.com] created the discussion

"Re: The reuse&&JBoss AOP"

To view the discussion, visit: http://community.jboss.org/message/585280#585280

In order to do that, first of all you need to change the signature of update method to something like this:

package Bee ;
public interface FlowerObserver {    
      public void update(boolean isOpen);

Now, your implementation must also receive the isOpen value as a parameter and that way you can check on whether the flower is open before deciding to either call Bee.dinner() or Bee.rest().

Another thing that you have to workaround is how to call this. JBoss AOP needs to control the creation of aspects. AFAIK, this is not a limiting factor exclusive to JBoss AOP, all AOP languages/tools need to have some control of how to create the aspect. So, you can't have as an aspect an  object you created yourself (i.e, it can't be the bees you are creating in main).

To workaround that:

- keep the interface as above
- add an Observable interface and a Mixin for that:
public interface Observable {
    public void addObserver(FlowerObserver observer);
    public void notifyAll();
public ObservableMixin {
    private Collection<FlowerObserver> observers = ...;
    private final Flower flower;
    public ObservableMixin(Flower flower) { this.flower = flower}
    public void addObserver(FlowerObserver observer) { observers.ad(observer);}
    public void notifyAll() { for(FlowerObserver: observers) { observer.update(flower.isOpen());}}

- and finally an after aspect that triggers the notification (use just the same xml you used, but replace BeeObserver update() by the ObserverAspect updateObservers advice below):

public class ObserverAspect() {
      public void updateObservers(@Target Observable observable) { observable.notifyAll(); }

- don't forget to add the ObservableMixin above to Flower class!

Now, in main, you can make:

((Observable) flower).addObserver((FlowerObserver) bee1);
((Observable) flower).addObserver((FlowerObserver) bee2);

And that's it!

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