[cdi-dev] Support Request (and Conversation?) Scope in @Singleton @Startup @PostConstruct methods

[Mark Struberg]

>>  @ConversationScoped EntityManager is broken, broken, broken. The EM is per 
> JPA spec NOT Serializable and thus must not get stored in the Session.
>>  There are some impls which _are_ Serializable, but those are not JPA spec 
> compliant (e.g. avajé eBean). With the mandatory support of locking and 
> pessimistic locking it is just technically impossible to implement a 
> Serializable EntityManager.
> 
> You can make this work (Seam 2 kinda did it with the Hibernate and a lot of code 
> to deal with entities being properly propagated - basically imposing 
> serialisation above the JVM layer) and I know the JBoss Clustering team are 
> looking at this. But it is a vendor specific solution only.
> 


Well, I know that there is some Hibernate mode which supports some serialization but in this mode 

.) it is not JPA compliant anymore
.) you will loose the 'state' of the entities after the serialisation
.) this was only JPA1
.) you will loose all pessimistic locks
.) it's not portable 


I still think that detaching after each request and merging it the next time works best for an EE 6 app.

LieGrue,
strub



----- Original Message -----
> From: Pete Muir <pmuir at redhat.com>
> To: Mark Struberg <struberg at yahoo.de>
> Cc: Guido Bonazza <guidbona at yahoo.com>; "cdi-dev at lists.jboss.org" <cdi-dev at lists.jboss.org>
> Sent: Tuesday, March 6, 2012 5:38 PM
> Subject: Re: [cdi-dev] Support Request (and Conversation?) Scope in @Singleton @Startup @PostConstruct methods
> 
> 
> On 6 Mar 2012, at 13:58, Mark Struberg wrote:
> 
>> 
>> 
>>  Folks, again and again and again: 
>> 
>> 
>>  @ConversationScoped EntityManager is broken, broken, broken. The EM is per 
> JPA spec NOT Serializable and thus must not get stored in the Session.
>>  There are some impls which _are_ Serializable, but those are not JPA spec 
> compliant (e.g. avajé eBean). With the mandatory support of locking and 
> pessimistic locking it is just technically impossible to implement a 
> Serializable EntityManager.
> 
> You can make this work (Seam 2 kinda did it with the Hibernate and a lot of code 
> to deal with entities being properly propagated - basically imposing 
> serialisation above the JVM layer) and I know the JBoss Clustering team are 
> looking at this. But it is a vendor specific solution only.
> 
>> 
>> 
>> 
>>>>    Moreover, quoting https://issues.jboss.org/browse/CDI-148 
> ("There is 
>>>  no reason why the ConversationScope should be any less available than 
> the 
>>>  RequestScope"),
>>  Well, there is a difference between a Servlet-Request and a JSF-Request. 
> The difference is subtle but important. The JSF-Request is e.g _not_ available 
> in some ServletFilters which are outside of the JSFs FacesServlet handling. The 
> CDI spec states this in 6.7.4:
>> 
>>>  If the conversation associated with the current JSF request is in the 
> transient state at the end of a JSF request,
>>>  it is destroyed, and the conversation context is also destroyed. 
>> 
>>  But the Request Context lives much longer! It will also be available in 
> various ServletFilters and Listeners. Thus the statement is not entirely 
> correct.
> 
> I think the statement is one of intent, not state. I.e. there is no reason it 
> should be less available.
> 
>> 
>> 
>>>  to be allowed to use it @Singleton @Startup @PostConstruct methods.
>>  Of which Beans are you talking here? EJBs? CDI managed beans? Which 
> @Singleton annotation? the one from JSR-330 or EJB?
>> 
>>  Please also note that the JSR-330 @Singleton is imo completely useless 
> because it's underspecified. "Singleton" in which _context_? 
>> 
>>  1 per WebApp?
>> 
>>  1 per EAR?
>>  1 per JVM?
>>  1 per Cluster?
>> 
>> 
>>  LieGrue,
>>  strub
>> 
>>  ----- Original Message -----
>>>  From: Pete Muir <pmuir at redhat.com>
>>>  To: Guido Bonazza <guidbona at yahoo.com>
>>>  Cc: "cdi-dev at lists.jboss.org" <cdi-dev at lists.jboss.org>
>>>  Sent: Tuesday, March 6, 2012 10:30 AM
>>>  Subject: Re: [cdi-dev] Support Request (and Conversation?) Scope in 
> @Singleton @Startup @PostConstruct methods
>>> 
>>>  Please file a CDI issue :-)
>>> 
>>>  On 2 Mar 2012, at 13:36, Guido Bonazza wrote:
>>> 
>>>>    Hello everyone!
>>>>    Checking out the CDI 1.0 spec and actually trying it on JBoss AS 
>>>  7.1.0.Final it seems to me that the Request Scope is not active in 
> @Singleton 
>>>  @Startup @PostConstruct method, so I'd like to propose this use 
> case to be 
>>>  supported in the next version of CDI.
>>>>    Moreover, quoting https://issues.jboss.org/browse/CDI-148 
> ("There is 
>>>  no reason why the ConversationScope should be any less available than 
> the 
>>>  RequestScope"), I think that conversation scope should be 
> available too in 
>>>  this context. It would be very useful, for example, when you have an 
>>>  EntityManager produced in conversation scope (mostly used in JSF 
> contexts), to 
>>>  be allowed to use it @Singleton @Startup @PostConstruct methods.
>>>>    Of course there should be some limitations in this case (long 
> running 
>>>  conversation promotion shouldn't be allowed for example), but the 
> basic case 
>>>  should be supported in my opinion.
>>>> 
>>>>    Thanks for the attention,
>>>>        Guido
>>>> 
>>>>    _______________________________________________
>>>>    cdi-dev mailing list
>>>>   cdi-dev at lists.jboss.org
>>>>   https://lists.jboss.org/mailman/listinfo/cdi-dev
>>> 
>>> 
>>>  _______________________________________________
>>>  cdi-dev mailing list
>>>  cdi-dev at lists.jboss.org
>>>  https://lists.jboss.org/mailman/listinfo/cdi-dev
>>> 
>> 
>>  _______________________________________________
>>  cdi-dev mailing list
>>  cdi-dev at lists.jboss.org
>>  https://lists.jboss.org/mailman/listinfo/cdi-dev
>