users@jpa-spec.java.net

[jpa-spec users] [jsr338-experts] Re: Inheritance of Extended Persistence Context

From: Scott Marlow <smarlow_at_redhat.com>
Date: Fri, 01 Jun 2012 13:00:56 -0400

On 06/01/2012 12:25 PM, michael keith wrote:
> Assuming the DAO interface is local and does not have a @Remote on it,
> and also assuming that there is just a forgotten injection annotation of
> @PersistenceContext(type=PersistenceContextType.EXTENDED) on the EM in
> TestService, then the PC should be inherited by both SFSBs DAO1 and
> DAO2. If the session beans are local then you should not leave the EJB
> container instance.
> (Does that answer the question?)

I think that you have answered my question about whether the beans would
be in the same EJB container instance. I don't think there will be
disagreement about that.

Regarding whether applications can portably expect the same behaviour
for this case is my other concern. We purposely are not specifying
@PersistenceContext(type=PersistenceContextType.EXTENDED) on the EM in
TestService to drive this discussion.

I think the current 7.6.3.1 wording is not clear enough about whether
the extended persistence context inheritance will occur between the
beans executing in the same EJB container instance.

I think that different vendors are handling this differently, which
impacts EE portability (IMO). I think that some vendors will inherit
the extended persistence context only if the beans parent (recursively
up to the top level bean) has the same persistence context. Other
vendors will inherit the extended persistence context only if another
bean with the same extended persistence context is executing in the same
EJB container instance.

I would like to clarify the intended behaviour that applications should
expect, or that it is implementation defined for this case (so
application writers can make a choice based on facts.)


>
> On 01/06/2012 11:50 AM, Scott Marlow wrote:
>> In the interest of ensuring EE application portability, I'd like to
>> change or add additional wording to the JPA 2.1 "7.6.3.1 Inheritance
>> of Extended Persistence Context" section.
>>
>> In the following example, instances of beans TestSFSB, DAO1, DAO2 will
>> be "executing in the same EJB container instance" (PostConstruct for {
>> TestSFSB, DAO1, DAO2} should execute in the same EJB container
>> instance). One question that I have, is there a possibility for {
>> TestSFSB DAO1, DAO2} to not execute in the same EJB container
>> instance? Is that EJB container implementation specific?
>>
>> @Stateful
>> @Remote(TestService.class)
>> public class TestSFSB implements TestService {
>> private EntityManager entityManager;
>>
>> @EJB(beanName = "DAO1") private DAO dao1;
>> @EJB(beanName = "DAO2") private DAO dao2;
>>
>> public String testfunc() {
>> dao1.myFunction();
>> dao2.myFunction();
>> return "fine";
>> }
>> }
>>
>> @Stateful
>> public class DAO1 implements DAO {
>> @PersistenceContext(type=PersistenceContextType.EXTENDED)
>> private EntityManager entityManager;
>>
>> public void myFunction() {
>> entityManager.find(PersonOrm.class, 123L);
>> System.out.println("DAO1:" + entityManager);
>> }
>> }
>>
>> @Stateful
>> public class DAO2 implements DAO {
>> @PersistenceContext(type=PersistenceContextType.EXTENDED)
>> private EntityManager entityManager;
>>
>> public void myFunction() {
>> entityManager.find(PersonOrm.class, 123L);
>> System.out.println("DAO2:" + entityManager);
>> }
>> }
>>
>>
>> Text from the JPA 2.0 specification:
>>
>> "
>> 7.6.2.1 Inheritance of Extended Persistence Context
>>
>> If a stateful session bean instantiates a stateful session bean
>> (executing in the same EJB container instance) which also has such an
>> extended persistence context, the extended persistence context of the
>> first stateful session bean is inherited by the second stateful
>> session bean and bound to it, and this rule recursively
>> applies—independently of whether transactions are active or not at the
>> point of the creation of the stateful session beans.
>> "
>>
>> Text from the JPA 2.1 specification:
>>
>> "
>> 7.6.3.1 Inheritance of Extended Persistence Context
>> If a stateful session bean instantiates a stateful session bean
>> (executing in the same EJB container instance) which also has such an
>> extended persistence context with the same synchronization type, the
>> extended persistence context of the first stateful session bean is
>> inherited by the second stateful session bean and bound to it, and
>> this rule recursively applies—independently of whether transactions
>> are active or not at the point of the creation of the stateful session
>> beans. If the stateful session beans differ in declared
>> synchronization type, the EJBException is thrown by the container.
>> "
>>
>> Depending on the answer to my first question, I'd like to add
>> clarifying text (to the JPA 2.1 7.6.3.1 section) that makes it more
>> obvious whether DAO1 + DAO2 (which could execute in the same EJB
>> container) will inherit the same extended persistence context. I'll
>> try to make some suggestions after we have answered these questions as
>> to whether DAO1 + DAO2 will always execute in the same EJB container.
>>
>> Scott
>>
>>