I got your point Jozef, and I fear you are right. This is just pretty dangerous in highly
concurrent scenarios :/
LieGrue,
strub
On Friday, 14 November 2014, 10:47, Jozef Hartinger
<jharting(a)redhat.com> wrote:
>
On 11/14/2014 09:14 AM, Mark Struberg wrote:
> I did not say it cannot work but that it is not guaranteed to work.
It's just totally up to implementation details of the container and your
actual situation. Basically it's non-portable at best.
>
>
> E.g. consider the case that you are NOT the outermost interceptor but there
are 2 other decorators and interceptors. The decorators will probably not hurt
much as they are defined to be called _after_ interceptors. But if there is an
interceptor in addition to yours then you will probably kill em and after
returning from the chain you might end up in a dead bean (the other
interceptor).
You are right Mark but I think this is not a problem of whether you call
AlterableContext.destroy() from within an interceptor or not. This is a
more general problem of destroying instances. Say you have an
intercepted @ApplicationScoped bean Foo. Thread 1 is calling an
intercepted method and is currently in the middle of the interceptor
chain. Thread 2 calls AlterableContext.destroy(Foo) in a Servlet (not
from an interceptor!). Foo is destroyed together with its interceptors
by Thread 2. Thread 1 finds itself executing a dead interceptor chain
for a destroyed bean.
>
> There are just so many things which can go wrong. Even though I like the
general idea what you like to do with that interceptor. But I suggest you
probably use another trick. Every CDI bean must (as per the interceptors spec)
support 'self-interception'. Means you only need to add an @AroundInvoke
method and do the re-setup of your CONNECTION inside your @ApplicationScoped
bean (with full access to the underlying business infrastructure).
>
>
> This is fundamentally different to your approach as I do not ditch the
whole service but only fix the thing which broke in it.
>
>
> LieGrue,
> strub
>
>
>
> On Thursday, 13 November 2014, 16:28, arjan tijms
<arjan.tijms(a)gmail.com> wrote:
>> Hi,
>>
>> On Wednesday, November 12, 2014, Jozef Hartinger
<jharting(a)redhat.com> wrote:
>>
>> Hi Arjan,
>>> there is a bug in Weld (WELD-1785) preventing this from working
which is going to be fixed in the next release. What you are doing should work
IMO as long as the interceptor does not call any other methods on the target
instance.
>>
>> That's great to hear really.
>>
>>
>> I'm slightly confused through why Mark thinks this cannot really
work, while you say it should.
>>
>>
>> Is there something in the spec that may need to be clarified here? Ie
some words about what an interceptor is at least allowed to do and what is
definitely not allowed?
>>
>>
>>
>> In addition it must count with the target instance being destroyed
within the instance.destroy() call.
>>
>>
>> Sorry, I don't fully follow this. You mean something must be
counted?
>>
>>
>>> Perhaps a nicer way of doing this would be:
>>>
>>> @Inject
>>> @Intercepted
>>> private Bean<?> bean;
>>>
>>> Context context = manager.getContext(bean.getScope());
>>> if (!(context instanceof AlterableContext)) {
>>> throw new IllegalStateException("Context does not
support removal of instances");
>>> }
>>> AlterableContext alterableContext =
AlterableContext.class.cast(context);
>>> alterableContext.destroy(bean);
>>
>> I tried something close to that as well, just used the bean manager to
resolve a Bean from the target object. Thanks for the suggestion!
>>
>>
>> Kind regards,
>> Arjan
>>
>>
>>
>>
>>> On 11/10/2014 02:59 PM, arjan tijms wrote:
>>>
>>> Hi,
>>>> I wonder if it would be allowed according to the CDI spec to
destroy a
>>>> bean instance from within an interceptor.
>>>>
>>>> To test this (on Weld) I used the following code:
>>>>
>>>> @Interceptor
>>>> @DestroyOnError
>>>> @Priority(APPLICATION)
>>>> public class DestroyOnErrorInterceptor implements Serializable
{
>>>>
>>>> private static final long serialVersionUID = 1L;
>>>>
>>>> @AroundInvoke
>>>> public Object tryInvoke(InvocationContext ctx) throws
Exception {
>>>>
>>>> try {
>>>> return ctx.proceed();
>>>> } catch (Exception e) {
>>>> destroy(ctx.getMethod().getDeclaringClass());
>>>> throw e;
>>>> }
>>>> }
>>>>
>>>> private <T> void destroy(Class<T> clazz)
{
>>>> Instance<T> instance =
CDI.current().select(clazz);
>>>> instance.destroy(instance.get());
>>>> }
>>>>
>>>> }
>>>>
>>>>
>>>> When I use this interceptor on a SessionScoped bean:
>>>>
>>>> @SessionScoped
>>>> public class TestBean implements Serializable {
>>>>
>>>> private static final long serialVersionUID = 1L;
>>>>
>>>> @DestroyOnError
>>>> public void test() {
>>>> throw new IllegalStateException();
>>>> }
>>>> }
>>>>
>>>> And then inject said bean in say a Servlet and call the test()
method,
>>>> destruction of the bean happens partially, but as soon as Weld
tried
>>>> to invocate a preDestroy method, it goes through the bean proxy
again,
>>>> detects that "the" interceptor handler is already
active, promptly
>>>> skips its attempt to call a preDestroy method and then to add
insult
>>>> to injury tries to call a "proceed" method which is
always null and
>>>> thus throws a NPE.
>>>>
>>>> (this happens in
>>>>
org.jboss.weld.bean.proxy.CombinedInterceptorAndDecoratorStackMethodHandler.invoke)
>>>>
>>>> I tried some alternative methods to destroy the bean such as:
>>>>
>>>>
>>>> Bean<T> bean = resolve(beanManager, beanClass);
>>>>
>>>> AlterableContext context = (AlterableContext)
>>>> beanManager.getContext(bean.getScope());
>>>> context.destroy(bean);
>>>>
>>>> with resolve being:
>>>>
>>>> public static <T> Bean<T> resolve(BeanManager
beanManager, Class<T> beanClass) {
>>>> Set<Bean<?>> beans =
beanManager.getBeans(beanClass);
>>>>
>>>> for (Bean<?> bean : beans) {
>>>> if (bean.getBeanClass() == beanClass) {
>>>> return (Bean<T>)
>>>>
beanManager.resolve(Collections.<Bean<?>>singleton(bean));
>>>> }
>>>> }
>>>>
>>>> return (Bean<T>) beanManager.resolve(beans);
>>>> }
>>>>
>>>> But this resulted in the same problem.
>>>>
>>>> Any idea?
>>>>
>>>> Kind regards,
>>>> Arjan Tijms
>>>> _______________________________________________
>>>> cdi-dev mailing list
>>>> cdi-dev(a)lists.jboss.org
>>>>
https://lists.jboss.org/mailman/listinfo/cdi-dev
>>>>
>>>> Note that for all code provided on this list, the provider
licenses the code under the Apache License, Version 2
(
http://www.apache.org/licenses/LICENSE-2.0.html). For all other ideas provided
on this list, the provider waives all patent and other intellectual property
rights inherent in such information.
>>>>
>> _______________________________________________
>> cdi-dev mailing list
>> cdi-dev(a)lists.jboss.org
>>
https://lists.jboss.org/mailman/listinfo/cdi-dev
>>
>> Note that for all code provided on this list, the provider licenses the
code under the Apache License, Version 2
(
http://www.apache.org/licenses/LICENSE-2.0.html). For all other ideas provided
on this list, the provider waives all patent and other intellectual property
rights inherent in such information.
>>
>>