Re: [aspectj-users] Was my aspect implementation overriden?

["John D. Heintz" <jheintz@xxxxxxxxx>]

Can ClassProvidingCustomImplementation.getMagicNumber call the default
implementation?

Thanks,
John

On 7/14/05, Adrian Colyer <adrian.colyer@xxxxxxxxx> wrote:
> Eyon wrote:
> 
> > I have created an aspect with inter-type method
> > declarations for classes that implement an interface.
> > Now some of the classes that use this interface will
> > override the implementation provided by the aspect.
> 
> > At runtime, is there a way to ask an instance whether
> > it overrode the method provided in the aspect?  I just
> > need to know this within the aspect that provided the
> > method!
> 
> There is no straightforward way to do this. Java reflection just sees
> that the class of the object has the method, and it appears as if it
> was directly declared in the class. However, if you are using AspectJ
> 5, this might be the first good use case I know of for the Java 5
> design that annotations on methods are *not* inherited.
> 
> When bug https://bugs.eclipse.org/bugs/show_bug.cgi?id=98901 is fixed
> (currently pending verification and integration of the attached
> patch), you will be able to write the following:
> 
> public interface AnInterface {}
> 
> public aspect ITDsOnInterface {
> 
>     @Retention(RetentionPolicy.RUNTIME)
>     @interface DefaultImplementation {}
> 
>     @DefaultImplementation
>     public int AnInterface.getMagicNumber() {
>         return 27;
>     }
> 
>     public boolean isUsingDefaultImpl(AnInterface obj) {
>         try {
>             return obj.getClass()
>                         .getDeclaredMethod("getMagicNumber")
>                         .isAnnotationPresent(DefaultImplementation.class);
>         } catch (NoSuchMethodException nsmEx) {
>             System.out.println("bang");
>             return false;
>         }
>     }
> }
> 
> public class ClassAcquiringDefaultImplementation implements AnInterface {}
> 
> public class ClassProvidingCustomImplementation implements AnInterface {
>     public int getMagicNumber() {
>         return 99;
>     }
> }
> 
> public class DefaultImplementationOrNot {
> 
>     public static void main(String[] args) {
>         ClassAcquiringDefaultImplementation obj1 =
>             new ClassAcquiringDefaultImplementation();
> 
>         ClassProvidingCustomImplementation obj2 =
>             new ClassProvidingCustomImplementation();
> 
>         System.out.println("default impl returns: " + obj1.getMagicNumber());
>         System.out.println("custom impl returns: " + obj2.getMagicNumber());
> 
>         System.out.println("isUsingDefaultImpl(obj1) returns " +
> 
> ITDsOnInterface.aspectOf().isUsingDefaultImpl(obj1));
>         System.out.println("isUsingDefaultImpl(obj2) returns " +
> 
> ITDsOnInterface.aspectOf().isUsingDefaultImpl(obj2));
>      }
> 
> }
> 
> -- Adrian
> adrian.colyer@xxxxxxxxx
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> 
> 


-- 
John D. Heintz
Software Craftsman
Austin, TX
(512) 633-1198

jheintz@xxxxxxxxx
http://johnheintz.homeip.net