Hi,
I'm pretttty sure there are AspectJ bugs in this area that you are hitting
(around advice and generics). Feels like this kind of thing is what you
wanted:
<T> List<T> makeDefensiveCopyOfReturnedList(final ProceedingJoinPoint
joinPoint) { .. }
what compile errors do you get? Maybe raise a bugzilla for it.
cheers,
Andy
On 4 February 2013 03:27, Rens van Leeuwen <[email protected]>wrote:
> Hi everybody,
>
> I've been trying to get a hierarchy of classes return defensive copies of
> instances of the Java Collections Framework. The idea is, that a caller
> should not be able to add/remove elements of a returned List<?> for
> instance, because the entity that returned that list should be the one
> managing it.
>
> I thought of using an aspect, and when trying to do so, I found out that
> it works, but it produces quite a bunch of warnings in both my Eclipse
> workspace as well as during weaving during a Maven build. I'm wondering if
> there's anything I can do to get rid of those warnings.
>
> I wrote the following class to define the aspect (stripped to only contain
> an example method):
>
> @Aspect
> public final class DefensiveCopyCollectionsReturningAspect {
>
> /**
> * Every 'getter' method in the portal model hierarchy that returns a
> * {@link List} should return a defensive copy so that calling clients
> * don't change the internal structure of the portal model.
> *
> * @param joinPoint The joinpoint.
> * @return An defensive copy of the returned list.
> */
> @SuppressWarnings("unchecked", "rawtypes")
> @Around("execution(public !static java.util.List<*>
> (AbstractPM+).get*())")
> public List makeDefensiveCopyOfReturnedList(final ProceedingJoinPoint
> joinPoint) {
> try {
> return new ArrayList((List) joinPoint.proceed());
> } catch (final Throwable exception) {
> throw new PortalRuntimeException(exception);
> }
> }
> }
>
> I've defined methods that do similar things for Set and Map as well, which
> works like a charm. However, since the return type of the method is
> java.util.List, without any generics involved, I see the following warnings:
>
> -- unchecked conversion when advice applied at shadow
> method-execution(java.util.List
> com.leanapps.portal.model.pension.participation.ParticipationPM.getDocuments()),
> expected java.util.List<com.leanapps.portal.model.report.DocumentPM> but
> advice uses java.util.List [Xlint:uncheckedAdviceConversion]
>
> Now here's the million (OK, maybe a little less ;)) dollar question: Is
> there any way to get the generics to work? I've tried several things, but
> they all don't seem to work. I've tried
>
> <T> List<T> makeDefensiveCopyOfReturnedList(final ProceedingJoinPoint
> joinPoint) { .. }
>
> which results in compilation errors:
>
> -- incompatible return type applying to method-execution(java.util.List
> com.leanapps.portal.model.pension.participation.ParticipationPM.getDocuments())
>
> If I try to add generics to the annotation:
>
> @Around("execution(public !static java.util.List<T+>
> (AbstractPM+).get*())")
>
> I see that no advice has been applied at all:
>
> -- advice defined in
> com.leanapps.portal.model.DefensiveCopyCollectionsReturningAspect has not
> been applied
>
> Hope that somebody on this list has an answer to this.
>
> Kind regards,
>
> Rens
>
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>
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