[webbeans-dev] Producer fields on EJBs

Fri Jul 31 10:57:31 EDT 2009

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
>>>>
>>>> _______________________________________________
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>>>> 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
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