Java Magazine - March/April 2012

method-specific decoration with @Decorator.

By implementing the interface, you will have to implement all methods in @Decorator (see Listing 15). The application server is going to inject your decorator instead of the real class. To achieve that, you have to introduce an interface shared by both the decorator and the Greeter bean. Now the interface is implemented by both classes, GreetDecorator as well as UniversalGreeter:

@Decorator public abstract class GreetDecorator implements Greeter{

@Inject @Delegate

Greeter greeter;

@Override
public String greet() {
return "Good " + greeter.greet();
}

}

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public class UniversalGreeter implements Greeter {}

fashion all methods of a class and introduce @Interceptors only if the plumbing can be provably reduced.

The Greeter interface is injected into the GreetingController instead of the UniversalGreeter realization. As in the interceptor case, you also have to activate the decorators in beans.xml first:

abstract decorators can be applied on a subset of methods to cover different aspects. Unlike interceptors, a decorator cannot be applied with an @Stereotype, because it is not sufficient for decoration. Decorators require an interface, which cannot be specified with the @Stereotype annotation.

Because the vast majority of all common cross-cutting concerns come with the platform, rarely will you find an obvious use case for AOP and, thus, for interceptors or decorators in Java EE. </article>

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<beans>

<class>(...).aop.decorators. GreetDecorator</class> </decorators>

</beans>

All questions related to injection, decoration, or interception in Java EE 6 can usually be answered with “yes.” Therefore, you should refine such questions and ask whether it is possible without custom extensions.

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By making the decorator abstract, you are not forced to implement all methods of the Greeter interface. Listing 16 shows partial decoration with abstract decorators.

You can choose methods to decorate and ignore the rest. Multiple

Although it seems like everything is possible in Java EE, you need only a subset of the AOP capabilities introduced here in real-world projects. In fact, I rarely use @InterceptorBinding and mostly rely on the pure @Interceptors annotation. I also tend to intercept in an all-or-nothing