[cdi-dev] Are we always able to invoke @PreDestroy for @Dependent beans?

[Mark Struberg]

Not sure about the Instance#destroy() this might lead to a bunch of other problems...
What about an additional Annotation to differentiate between beans which should get tracked and ones who should not?

... still trying to get the whole picture ...

LieGrue,
strub



----- Original Message -----
> From: Marek Schmidt <maschmid at redhat.com>
> To: cdi-dev at lists.jboss.org
> Cc: 
> Sent: Friday, March 9, 2012 6:37 PM
> Subject: Re: [cdi-dev] Are we always able to invoke @PreDestroy for @Dependent beans?
> 
> On 09/03/12 17:47, Pete Muir wrote:
>>  I would propose we add Instance.destroy() as well, to make it easier…
> 
> and what would happen if the bean is not @Dependent? (I would think it
> should be no-op for those, as otherwise I would need to start caring
> about the scope of the bean I am injecting via Instance.get()... but
> then, such API would probably be a bit confusing...
> 
> --
> Marek Schmidt
> 
>> 
>>  On 9 Mar 2012, at 16:45, Mark Struberg wrote:
>> 
>>>  Well, I think the newly proposed wording is still fine (sharing the 
> CreationalContext of the @Dependent beans created by Instance.get() with the 
> InjectionPoint. 
>>> 
>>> 
>>>  What we need to do is to point people at manually creating the beans if 
> they don't like this behaviour.
>>>  In that case they still can use
>>>  BeanManager#getBeans + bm#resolve + bm#getReference 
>>>  storing away the CreationalContext and later throw them away manually 
> with bean.destroy.
>>> 
>>> 
>>>  LieGrue,
>>>  strub
>>> 
>>> 
>>>  ----- Original Message -----
>>>>  From: Pete Muir <pmuir at redhat.com>
>>>>  To: Jozef Hartinger <jharting at redhat.com>
>>>>  Cc: Mark Struberg <struberg at yahoo.de>; cdi-dev 
> <cdi-dev at lists.jboss.org>
>>>>  Sent: Thursday, March 8, 2012 11:35 PM
>>>>  Subject: Re: [cdi-dev] Are we always able to invoke @PreDestroy for 
> @Dependent beans?
>>>> 
>>>>  T his is still an issue for Instance.get() :-(
>>>> 
>>>>  On 8 Mar 2012, at 15:47, Jozef Hartinger wrote:
>>>> 
>>>>>  I think you are wrong. The spec says:
>>>>> 
>>>>>  "Any instance of the bean injected into method parameters 
> of a 
>>>>  disposer 
>>>>>  method or observer method exists to service the
>>>>>  method invocation only (except for observer methods of 
> container 
>>>>>  lifecycle events)."
>>>>> 
>>>>>  So the instance should actually be destroyed immediately after 
> the 
>>>>>  observer method invocation finishes.
>>>>> 
>>>>>  On 03/08/2012 01:47 PM, Mark Struberg wrote:
>>>>>>  My answer sadly is no.
>>>>>> 
>>>>>>  Dependent objects are stored in the CreationalContext which 
> is held in 
>>>>  the context which holds the outer NormalScoped contextual instance.
>>>>>>  If the outer NormalScoped contextual instance gets 
> desroyed, we also 
>>>>  properly destroy all @Dependent beans in the CreationalContext.
>>>>>> 
>>>>>>  So far so good, but now let's consider hte following 
> scenario:
>>>>>> 
>>>>>> 
>>>>>>  @ApplicationScoped
>>>>>>  public class MyService {
>>>>>> 
>>>>>>     void doStats(@Observes RequestStatistics, UserHelper uh) 
> {
>>>>>> 
>>>>>> 
>>>>>>  UserHelper is @Dependent and a new instance will get 
> created each time 
>>>>  doStats() gets called.
>>>>>> 
>>>>>>  What happens is that we don't know whether the 
> UserHelper 
>>>>  internally gets stored or just thrown away. In our sample most 
> probably the 
>>>>  later.
>>>>>>  Each UserHelper will get stored in the CreationalContext of 
> our single 
>>>>  MyService instance. After 500.000 requests, our CreationalContext 
> would contain 
>>>>  500.000 UserHelpers. Not smart, eh? This would just create a fat 
> memory leak...
>>>>>> 
>>>>>> 
>>>>>>  What we can do is to store only WeakReferences. E.g. via a 
> WeakHashmap. 
>>>>  This will automatically drop the entries if the instances in it get 
> garbage 
>>>>  collected. But in this case are not able to invoke @PreDestroy 
> anymore I fear, 
>>>>  because gone is gone ...
>>>>>> 
>>>>>>  LieGrue,
>>>>>>  strub
>>>>>> 
>>>>>> 
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>> 
>> 
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