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

[Pete Muir]

I think we have to offer both options. One which in which @PreDestroy is reliably invoked but with memory impact, other in which it's not reliable.

Which one should be the default?

On 8 Mar 2012, at 12:47, 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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