[cdi-dev] Managing Dependent Scoped Beans

[Martin Kouba]

Dne 15.5.2016 v 17:14 John D. Ament napsal(a):
> Romain,
>
> On Sun, May 15, 2016 at 11:05 AM Romain Manni-Bucau
> <rmannibucau at gmail.com <mailto:rmannibucau at gmail.com>> wrote:
>
>     Hi Jon
>
>     Le 15 mai 2016 16:15, "John D. Ament" <john.d.ament at gmail.com
>     <mailto:john.d.ament at gmail.com>> a écrit :
>      >
>      > Hey guys
>      >
>      > Seems like we have some issues in JIRA all focused on managing
>     the lifecycle of Dependent scoped beans.  It also seems like we have
>     many differing opinions about how to manage them.
>      >
>      > - Martin raised a PR to add a release() method to Instance to
>     help destroy a dependent bean https://github.com/cdi-spec/cdi/pull/286
>      > - I raised a PR https://github.com/cdi-spec/cdi/pull/289 to
>     update the spec to clarify how to manage a dependent scoped bean.
>      >
>      > Right now, it seems that the big disagreement is whether
>     Instance.destroy() can destroy objects not created by it (the case
>     being around the CDI utility class, being an impl of Instance).  I'm
>     currently heavily against Martin's proposed changes, but want to get
>     input from others on the group to understand their perspective.
>      >
>      > - Does the spec require destroy() to be called only on instances
>     that it created?  When I read 5.6.1 the only requirement I see is
>     that it has to be a dependent scoped bean.  Note when I ask this I'm
>     asking from the spec perspective, its a different problem if there's
>     some issues with implementations following suite (I would imagine
>     there needs to be some shared global registry of dependent scoped
>     beans for this to work).
>      >
>
>     Sound the only clean impl. Any other is not symmetric and
>     potentially lead to "oops this time it didnt work". I also not
>     seeing any use case limitation with that so think it is the same
>     solution
>
>
> I'm not sure I follow or if this isn't an answer to "Does the spec
> require destroy() to be called only on instances that it created?" ?
>
> Anyways I did look a bit closer and it seems that Martin's statement is
> consistent with how OWB works,
> https://github.com/apache/openwebbeans/blob/trunk/webbeans-impl/src/main/java/org/apache/webbeans/inject/instance/InstanceImpl.java#L293 so
> I wonder if there's a part of the spec I'm missing, or if there was some
> offline agreement on how to understand it.

John, I believe Instance CANNOT be used to destroy a dependent bean 
instance it didn't created, because a dependent bean instance doesn't 
know the dependent objects it depends on - that's what CreationalContext 
is for.

So if you pass any dependent instance to Instance.destroy() there is no 
CreationalContext apart from the one Instance<> has. In other words you 
wouldn't be able to destroy the @Dependent dependencies of a @Dependent 
bean instane. Does it make sense?

See also https://issues.jboss.org/browse/CDI-519 (cdi-spec/cdi/pull/278 
is already merged).


>
> John
>
>      > - Do we want two methods that effectively do the same thing?  I
>     don't see a strong difference between the two.
>      >
>      > On the flipside, my change is more a spec clarification.  I'm
>     thinking more now that it belongs as a reword of 5.6.1 to clarify
>     how to use destroy() on dependent beans, rather than where I put
>     it.  I think realistically we have all of the tools needed to manage
>     the lifecycle of these classes, just need to clarify them for people
>     to use.
>      >
>      > John
>      >
>
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-- 
Martin Kouba
Software Engineer
Red Hat, Czech Republic