Method Interceptor with Annotation Arguments

[Sasha Bermeister]

Hi all,

I've been following the tutorial on AOP at https://code.google.com/p/google-guice/wiki/AOP. In the tutorial, it shows how to use an annotation with no arguments:

public class RealBillingService implements BillingService {

  @NotOnWeekends
  public Receipt chargeOrder(PizzaOrder order, CreditCard creditCard) {
    ...
  }
}

For my application, I need this annotation to take arguments, e.g.:

@NotOnWeekends("Foo")

And these arguments need to be accessible from within the MethodInterceptor itself (since I need to perform something different based on what the arguments might be).

I've looked around for guides and tutorials, but nothing seems to cover this particular case. Any ideas?

Thanks,

Sasha

[Laszlo Ferenczi]

Hi Sasha,

You can access all annotations on the method and/or the defining class using the MethodInvocation parameter of MethodInterceptor.invoke(). Something like this:

public class MyInterceptor implements MethodInterceptor {

    public Object invoke(MethodInvocation methodInvocation) throws Throwable {

        Method method = methodInvocation.getMethod();

        MyAnnotation annotation = method.getAnnotation(Transactional.class);

        ....

    }

}

For a full example check out guice-persist's transactional interceptor:

https://code.google.com/p/google-guice/source/browse/extensions/persist/src/com/google/inject/persist/jpa/JpaLocalTxnInterceptor.java

Line 56 is where the annotation is extracted. 

HTH

--
L

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