[cdi-dev] Destroying @Stateless proxies obtained via CDI.current().select()

[arjan tijms]

Hi Martin,

Thanks for the swift action and the reference. I do have one more question
looking at the test that was added. It now uses this SLSB:

@Stateless
public class SLSessionBean {

    public void ping(){
    }

    static final AtomicBoolean DESTROYED = new AtomicBoolean();

    @PreDestroy
    public void destroy() {
        DESTROYED.set(true);
    }
}

The assertion in the test is that the (a?) SLSB is actually destroyed, but
wasn't the idea that only the internal reference is destroyed, and the bean
just stays in the pool?

Here it looks like the code intends to destroy a random SLSB instance from
the pool. (random, since I guess an internal reference doesn't stick to the
same actual instance of a SLSB, otherwise you would get stateful like
semantics).

Or did I miss something?

Kind regards,
Arjan Tijms




On Wed, May 11, 2016 at 9:11 AM, Martin Kouba <mkouba at redhat.com> wrote:

> Hi Arjan,
>
> I believe it's a Weld bug - you should be able to use Instance.destroy()
> to discard an internal SLSB proxy. See also "Lifecycle of stateless and
> singleton session beans" [1]. Tomas Remes created WELD-2148 to track this
> issue [2].
>
> Also the "leak" is an expected behaviour. See for example WELD-920 [3]
> discussion.
>
> Martin
>
> [1]
> http://docs.jboss.org/cdi/spec/1.2/cdi-spec.html#stateless_lifecycle
>
> [2]
> https://issues.jboss.org/browse/WELD-2148
>
> [3]
> https://issues.jboss.org/browse/WELD-920
>
> Dne 10.5.2016 v 17:11 arjan tijms napsal(a):
>
>> Hi,
>>
>> Given a simple @Stateless bean:
>>
>> @Stateless
>> public class Foo {
>>      public void bar() {}
>> }
>>
>> Then requesting an instance of this via CDI as follows:
>>
>> Foo foo = CDI.current().select(Foo.class).get();
>>
>> Causes a lot of leaked proxy instances (at least on Weld). Now what I
>> guess needs to be done is destroying the proxy, taking Antoine's answer
>> here as a lead:
>> http://stackoverflow.com/questions/28767536/scope-of-stateless-bean
>>
>> Only the following throws an UnsupportedOperationException (on Weld
>> 2.3.2, haven't tested OWB yet)
>>
>> Instance<Foo> fooInstance =CDI.current().select(Foo.class);
>> Foo foo = fooInstance.get();
>> foo.bar();
>> fooInstance.destroy(foo);
>>
>> The question is, is this how it's supposed to be done via the spec?
>>
>> Implementation wise, what happens in Weld is that the CDI/EJB proxy
>> (com.test.Foo$Proxy$_$$_Weld$EnterpriseProxy$) in the following code
>> doesn't hit the check for a dependent instance (comments in capitals
>> added by me):
>>
>>
>>      public void destroy(T instance) {
>>          Preconditions.checkNotNull(instance);
>>
>>          // check if this is a proxy of a normal-scoped bean
>>          if (instance instanceof ProxyObject) {
>>
>>              // THIS BRANCH IS TAKEN FOR CDI/EJB PROXY
>>
>>              ProxyObject proxy = (ProxyObject) instance;
>>              if (proxy.getHandler() instanceof ProxyMethodHandler) {
>>                  ProxyMethodHandler handler = (ProxyMethodHandler)
>> proxy.getHandler();
>>                  Bean<?> bean = handler.getBean();
>>                  Context context =
>> getBeanManager().getContext(bean.getScope());
>>                  if (context instanceof AlterableContext) {
>>                      AlterableContext alterableContext =
>> (AlterableContext) context;
>>
>>                      // CONTEXT IS A DEPENDENTCONTEXTIMPL THAT THROWS
>>                      // UnsupportedOperationException FROM ITS DESTROY()
>> METHOD
>>                      alterableContext.destroy(bean);
>>                      return;
>>                  } else {
>>                      throw BeanLogger.LOG.destroyUnsupported(context);
>>                  }
>>              }
>>          }
>>
>>          // check if this is a dependent instance
>>          CreationalContext<? super T> ctx = getCreationalContext();
>>          if (ctx instanceof WeldCreationalContext<?>) {
>>              WeldCreationalContext<? super T> weldCtx = cast(ctx);
>>
>>              // PROXY REFERENCES ARE KEPT HERE IN A
>>              // "dependentInstances" LIST, AND WOULD BE CLEARED HERE
>>              // BUT THIS CODE IS NEVER REACHED
>>              weldCtx.destroyDependentInstance(instance);
>>          }
>>      }
>>
>> Now I wonder, am I doing something wrong (according to the CDI spec), or
>> could this be a bug in the Weld code?
>>
>> Kind regards,
>> Arjan Tijms
>>
>>
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>>
> --
> Martin Kouba
> Software Engineer
> Red Hat, Czech Republic
>
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