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

[Martin Kouba]

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