[webbeans-dev] Producer fields on EJBs

Pete Muir pmuir at redhat.com
Fri Jul 31 10:58:51 EDT 2009 

ALR, Carlo, Jaikiran, can one of you join? It's at

> Date: Jul 31st 2009
> Time: 9:30 to 10:30am PST
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On 31 Jul 2009, at 15:57, Kenneth Saks wrote:

>
> On Jul 31, 2009, at 10:52 AM, Pete Muir wrote:
>
>> Hi Guys,
>>
>> We need to resurrect this discussion.
>
> Why don't we go over this on today's concall.
>
>>
>> I've committed a proposed SPI getFieldValue() method to http://anonsvn.jboss.org/repos/webbeans/ri/trunk/spi/src/main/java/org/jboss/webbeans/ejb/api/SessionObjectReference.java 
>>  which I will wire into Web Beans now.
>>
>> Can anyone say if they vehemently disagree with this approach, or  
>> have some improvements to suggest? :-)
>>
>> Thanks!
>>
>> Pete
>>
>> On 16 Apr 2009, at 07:51, Andrew Lee Rubinger wrote:
>>
>>> Pete Muir wrote:
>>>> I thought through this some, and bounced ideas off Andy.
>>>> Gavin, I'm not sure that producer fields on SLSBs makes much  
>>>> sense - SLSBs instance state is undefined I think (some EJB  
>>>> expert correct if I'm wrong ;-). I think the spec should say that  
>>>> the behaviour of producer fields on SLSBs is undefined.
>>>> Assuming the above, I would still argue for a getFieldValue SPI  
>>>> that throws IllegalStateException if invoked on an SLSB reference  
>>>> - and I think this removes the issue Ken has with a many-to-one  
>>>> instances.
>>>
>>> UnsupportedOperationException perhaps?
>>>
>>>> I'm slipping this for the upcoming release as we are too far from  
>>>> consensus.
>>>> On 6 Apr 2009, at 18:22, Pete Muir wrote:
>>>>>
>>>>> On 6 Apr 2009, at 18:00, Kenneth Saks wrote:
>>>>>
>>>>>>
>>>>>> On Apr 6, 2009, at 12:31 PM, Pete Muir wrote:
>>>>>>
>>>>>>> Carlo, Ken, Andrew,
>>>>>>>
>>>>>>> JSR-299 supports the notion of a producer field. By adding the  
>>>>>>> annotation @Produces to a field, you make it into a bean,  
>>>>>>> which can be used as the source of injections. The field can  
>>>>>>> also be associated with a scope. When you first look up an  
>>>>>>> instance of a bean, the field value is accessed, and stored in  
>>>>>>> the context for it's lifetime.
>>>>>>>
>>>>>>> As we deal with EJB references, we can't directly access the  
>>>>>>> field value (using reflection) so I think we should use the  
>>>>>>> SPI here.
>>>>>>>
>>>>>>> I propose we add a method with this signature to the  
>>>>>>> SessionObjectReference we previously created for the purpose  
>>>>>>> of casting/removing EJBs https://svn.jboss.org/repos/webbeans/ri/trunk/spi/src/main/java/org/jboss/webbeans/ejb/api/SessionObjectReference.java
>>>>>>
>>>>>> There isn't necessarily a one-to-one relationship between an  
>>>>>> ejb reference and a bean instance.   For stateless session  
>>>>>> beans, any one of the bean instances can be used for any  
>>>>>> invocation.
>>>>>>
>>>>>> Can't this behavior be handled by the web beans interceptor?   
>>>>>> By definition, each interceptor instance has the same life  
>>>>>> cycle as its associated bean instance, and the bean instance is  
>>>>>> available via the Interceptor InvocationContext.
>>>>>
>>>>> I did consider this, but not sure how to retrieve the result  
>>>>> invocationContext.getTarget() at the time it is needed for  
>>>>> accessing the producer field. We can't just store it from the  
>>>>> construction point onwards (serializability) and I can't see a  
>>>>> way to access it at some other point in the lifecycle - the only  
>>>>> way to run an @AroundInvoke is to call a method, and in this  
>>>>> case which method would you run, and how would you guarantee it  
>>>>> has no side effects?
>>>>>
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> /**
>>>>>>> * Retrieve the value of a (possibly private) field
>>>>>>> *
>>>>>>> * @param field
>>>>>>> *           the field to retrieve the value of
>>>>>>> * @return the retrieved value
>>>>>>> * @throws IllegalArgumentException
>>>>>>> *            if the field doesn't exist on this session object  
>>>>>>> instance
>>>>>>> */
>>>>>>> public Object getFieldValue(Field field);
>>>>>>>
>>>>>>> Any comments?
>>>>>>>
>>>>>>>
>>>>>>> On 29 Mar 2009, at 22:57, Pete Muir wrote:
>>>>>>>
>>>>>>>> Ok, I would think that some language in the spec to hint at  
>>>>>>>> this might be good, as instances of session beans elsewhere  
>>>>>>>> in the spec implies a EJB reference.
>>>>>>>>
>>>>>>>> On 29 Mar 2009, at 18:04, Gavin King wrote:
>>>>>>>>
>>>>>>>>> Yes, this is a good question - the 299 implementation would  
>>>>>>>>> need
>>>>>>>>> direct integration with the EJB container for this. (Not the  
>>>>>>>>> only
>>>>>>>>> place this is needed.)
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Sat, Mar 28, 2009 at 7:18 PM, Pete Muir  
>>>>>>>>> <pmuir at redhat.com> wrote:
>>>>>>>>>> Hey
>>>>>>>>>>
>>>>>>>>>> Not quite sure how this is supposed to work as everywhere  
>>>>>>>>>> we hold a
>>>>>>>>>> reference (proxy) to the EJB, and therefore don't have  
>>>>>>>>>> access to the
>>>>>>>>>> instance and therefore can't get hold of the fields. Any  
>>>>>>>>>> pointers?
>>>>>>>>>>
>>>>>>>>>> Thanks!
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> -- 
>>>>>>>>>> Pete Muir
>>>>>>>>>> http://www.seamframework.org
>>>>>>>>>> http://in.relation.to/Bloggers/Pete
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> -- 
>>>>>>>>> Gavin King
>>>>>>>>> gavin.king at gmail.com
>>>>>>>>> http://in.relation.to/Bloggers/Gavin
>>>>>>>>> http://hibernate.org
>>>>>>>>> http://seamframework.org
>>>>>>>>
>>>>>>>> -- 
>>>>>>>> Pete Muir
>>>>>>>> http://www.seamframework.org
>>>>>>>> http://in.relation.to/Bloggers/Pete
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> webbeans-dev mailing list
>>>>>>>> webbeans-dev at lists.jboss.org
>>>>>>>> https://lists.jboss.org/mailman/listinfo/webbeans-dev
>>>>>>>
>>>>>>> -- 
>>>>>>> Pete Muir
>>>>>>> http://www.seamframework.org
>>>>>>> http://in.relation.to/Bloggers/Pete
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> webbeans-dev mailing list
>>>>>> webbeans-dev at lists.jboss.org
>>>>>> https://lists.jboss.org/mailman/listinfo/webbeans-dev
>>>>>
>>>>> -- 
>>>>> Pete Muir
>>>>> http://www.seamframework.org
>>>>> http://in.relation.to/Bloggers/Pete
>>>>>
>>>>> _______________________________________________
>>>>> webbeans-dev mailing list
>>>>> webbeans-dev at lists.jboss.org
>>>>> https://lists.jboss.org/mailman/listinfo/webbeans-dev
>>>> -- 
>>>> Pete Muir
>>>> http://www.seamframework.org
>>>> http://in.relation.to/Bloggers/Pete
>>>> _______________________________________________
>>>> webbeans-dev mailing list
>>>> webbeans-dev at lists.jboss.org
>>>> https://lists.jboss.org/mailman/listinfo/webbeans-dev
>>>
>>> -- 
>>> Andrew Lee Rubinger
>>> Sr. Software Engineer
>>> JBoss, a division of Red Hat, Inc.
>>> http://exitcondition.alrubinger.com
>>> _______________________________________________
>>> webbeans-dev mailing list
>>> webbeans-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/webbeans-dev
>>
>

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