| Re: [aspectj-users] Generics in return types causing warnings |
Hi Andy. I found a pretty similar problem on StackOverflow: http://stackoverflow.com/questions/15110442/how-to-handle-generic-result-with-aspectj Because the guy who asked the question had a lot of dependencies in his sample code, I reproduced the problem using some dummy classes, see my answer: http://stackoverflow.com/a/15448896/1082681 For your convenience I am also adding my sample project for you to play around with. Maybe it helps to analyse the problem. Good Luck! -- Alexander Kriegisch http://scrum-master.de Andy Clement, 12.02.2013 19:26: > 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. > > > On 4 February 2013 03:27, Rens van Leeuwen > <rens.van.leeuwen@xxxxxxxxxxxx <mailto:rens.van.leeuwen@xxxxxxxxxxxx>> > wrote: > > 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
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