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POAOP or APT for overriding methods from super classes
 

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    <p>I have a large library of wicket components that are annotated with a custom annotation <code>@ReferencedResource</code> or another annotation <code>@ReferencedResources</code>, that has a <code>ReferencedResouce[] value()</code> parameter to allow multiple annotations.</p> <p>Here is a sample code snippet:</p> <pre><code>@ReferencedResources({ @ReferencedResource(value = Libraries.MOO_TOOLS, type = ResourceType.JAVASCRIPT), @ReferencedResource(value = "behaviors/promoteSelectOptions", type = ResourceType.JAVASCRIPT) }) public class PromoteSelectOptionsBehavior extends AbstractBehavior{ ... } </code></pre> <p>So far, I use <a href="http://download.oracle.com/javase/6/docs/api/javax/annotation/processing/package-summary.html" rel="nofollow noreferrer">apt</a> to check that the referenced resources actually exist. E.g. </p> <pre><code>@ReferencedResource(value = "behaviors/promoteSelectOptions", type = ResourceType.JAVASCRIPT) </code></pre> <p>will cause a compilation failure unless the file <code>js/behaviors/promoteSelectOptions.js</code> can be found on the class path. This part works nicely.</p> <p>Now I am also a fan of DRY and I would like to use the same annotation to actually inject the resources into the Objects when they are created. Using AspectJ, I have implemented a part of this.</p> <p>The annotated Objects are always either instances of <a href="http://wicket.apache.org/apidocs/1.4/org/apache/wicket/Component.html" rel="nofollow noreferrer">Component</a> or <a href="http://wicket.apache.org/apidocs/1.4/org/apache/wicket/behavior/AbstractBehavior.html" rel="nofollow noreferrer">AbstractBehavior</a>.</p> <p>For components, things are easy, just match after the constructor. Here's an advice that does this:</p> <pre><code>pointcut singleAnnotation() : @within(ReferencedResource); pointcut multiAnnotation() : @within(ReferencedResources); after() : execution(Component+.new(..)) &amp;&amp; (singleAnnotation() || multiAnnotation()){ final Component component = (Component) thisJoinPoint.getTarget(); final Collection&lt;ReferencedResource&gt; resourceAnnotations = // gather annotations from cache this.getResourceAnnotations(component.getClass()); for(final ReferencedResource annotation : resourceAnnotations){ // helper utility that handles the creation of statements like // component.add(JavascriptPackageResource.getHeaderContribution(path)) this.resourceInjector.inject(component, annotation); } } </code></pre> <p>For behaviors however, I need to attach the resources to a response, not to the behavior itself. Here are the pointcuts I use:</p> <pre><code>pointcut renderHead(IHeaderResponse response) : execution(* org.apache.wicket.behavior.AbstractBehavior+.renderHead(*)) &amp;&amp; args(response); </code></pre> <p>And here is the advice:</p> <pre><code>before(final IHeaderResponse response) : renderHead(response) &amp;&amp; (multiAnnotation() || singleAnnotation()) { final Collection&lt;ReferencedResource&gt; resourceAnnotations = this.getResourceAnnotations(thisJoinPoint.getTarget().getClass()); for(final ReferencedResource resource : resourceAnnotations){ this.resourceInjector.inject(response, resource); } } </code></pre> <p>This also works nicely if the class overrides the <a href="http://wicket.apache.org/apidocs/1.4/org/apache/wicket/behavior/AbstractBehavior.html#renderHead%28org.apache.wicket.markup.html.IHeaderResponse%29" rel="nofollow noreferrer">renderHead(response)</a> method, but in many cases that's just not necessary because a super class already implements the base functionality while the child class only adds some configuration. So one solution would be to let these classes define a method like this:</p> <pre><code>@Override public void renderHead(IHeaderResponse response){ super.renderHead(response); } </code></pre> <p>I would hate this, because this is dead code, but currently this is the only working option I see, so I am looking for other solutions.</p> <p>EDIT:</p> <p>I have created a working solution using APT and sun javac calls. However, this leads to the next problem: <a href="https://stackoverflow.com/questions/3660547/apt-and-aop-in-the-same-project-using-maven">Running APT and AspectJ in the same project using maven</a>.</p> <p>Anyway, as soon as I have some free time, I'll post the answer to this question (or parts of it).</p>
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