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POCalling methods declared in an aspect
 

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    <p><a href="http://eclipse.org/aspectj/doc/released/progguide/starting-aspectj.html#inter-type-declarations" rel="nofollow">This page</a> shows how one can add methods to existing classes and then shows how to declare methods inside the aspect that call those additional methods.</p> <p>This is the code from that page:</p> <pre><code>aspect PointObserving { private Vector Point.observers = new Vector(); public static void addObserver(Point p, Screen s) { p.observers.add(s); } public static void removeObserver(Point p, Screen s) { p.observers.remove(s); } pointcut changes(Point p): target(p) &amp;&amp; call(void Point.set*(int)); after(Point p): changes(p) { Iterator iter = p.observers.iterator(); while ( iter.hasNext() ) { updateObserver(p, (Screen)iter.next()); } } static void updateObserver(Point p, Screen s) { s.display(p); } } </code></pre> <p>I am trying to reuse this pattern in the same setting (observer pattern) but I want to be able to add observers from anywhere in my Java code. Thus, in the example shown on that page, I want to do something like this from another class in my package:</p> <pre><code>Point p = new Point(120, 230); Screen s = getScreen(); PointObserving.addObserver(p, s); </code></pre> <p>However, the "aspect" PointObserving is not visible to my Java classes (though I have declared it public).</p>
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    1. USApoorv Khurasia
    1. USApoorv Khurasia
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    1. CO`PointObserving`, in this case, is an aspect that is woven into your code ***after*** it has been compiled. Your classes will not be aware of any of the woven code because from their point of view, it doesn't exist. If you want to mimic what was done in this particular aspect, consider using the standard Observable/Observer from the SDK.
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    2. COI think you should reconsider your motives for using AOP - or try to understand what it is all about. AOP is for separately modelling crosscutting concerns and for getting rid of scattering and tangling of secondary concerns in your core code. So try to refrain from scatter and tangle everything again through the back door. Instead, try to find a way to apply your Observer pattern by means of AOP. I am sure there must be a way to do that cleanly without creating an application design nightmare.
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      1. USkriegaex
    3. CO@kriegaex I am indeed trying to apply the observer pattern through AOP. My motive is simple. I want to trace (not by means of logging but by intercepting method args/returned values at some specific points in the calculations) a complete calculation. Now, I have this these different models (that do these calculations) but I do not want to clutter them by adding listener.doThis()/doThat() methods in the midst of my business logic. I think AOP fits the requirements neatly. I think I have found a solution that works. Will post it to see if you/others see a problem with it.
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      1. USApoorv Khurasia
 

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