Re: [cdi-dev] Is the concept of mutable event payload specified

----- Original Message ----- > Ok guys, > > Let’s do it again. I didn’t say we have to forbid the mutability I said we > have at least to explicitly write that it’s mutable and seriously think of > having it immutable for event fired asynchronously. > > > (Pete) I don’t think it’s specified. As objects are, by default in Java, > > mutable, I would assume that payloads are implicitly mutable. > > > Sorry @Pete I don’t agree with your point. Yes, in Java object are mutable > but firing an event is not a standard Java feature : you send your object to > a black box and let this box dispatch your object to listeners transforming > one call to multiple call : it’s far from standard Java rules. Even if it’s > not written it’s an observer pattern and there are people out there thinking > that introducing mutability in observer is an anti-pattern since some > listener will receive a different payload than the one that was sent to > them. I agree it should be tidied up. I'm simply stating that currently I would interpret the spec as allowing mutable payloads. > It’s like making a method call and having no guarantee that the parameter > received in the callee has the same value that in the caller... > I won’t start discussion on bad practice or anti pattern as I also use > mutability in event but there as much reason for user to assume their > payload will be mutable than the other way around. > I can assure you that when I give a talk on CDI, this payload mutability is > often a surprise for attendees... > > > (Romain) why isn't it portable? > > > So yes @Romain it’s not portable (in theory of course, since both > implementations support mutability). Someone could write a CDI > implementation with event payload immutability without any issue with the > spec and TCK. > > Most of you are so dependent of this feature that you only reacted to the > idea or forbidding it (which wasn’t the content of my mail) ;). So we all > agree that it’s an important feature. Therefore what’s the issue to specify > this mutability and add TCK test for it ? > > Now I don’t deal with that subject for nothing, we are planning to introduce > Async events. I think that it’ll bring extra complexity if we support > mutability in async events. And even if I’m wrong and we finally go for > mutability in async events, this will lead to possible side effect (lock) > that could have impact on perf, so it should be explicitly written IMO. > > Antoine > > > > > > > > _______________________________________________ cdi-dev mailing list cdi-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/cdi-dev Note that for all code provided on this list, the provider licenses the code under the Apache License, Version 2 ( http://www.apache.org/licenses/LICENSE-2.0.html). For all other ideas provided on this list, the provider waives all patent and other intellectual property rights inherent in such information.