Karl,
Mostly because ConversationScope beans must be serializable and the EM is not (check the "transient" keyword on the variable that
keeps in the ConversationScope Holder) and the fact that in our web apps, the EM can be injected in components where the
ConversationScope is not active (Namely MDBs and JAX-WS endpoints), where there is only one "request" and no need to get the same
EM. For this we use another layer (Check my previous posts about our the "EntityResolver" interface and implementations)
Denis
Le 2015-04-19 14:33, Karl Kildén a écrit :
Denis,
What's the added benefit of wrapping the em in @ConversationScoped instead
of exposing it like this directly. I am also porting a huge seam app (about
1k views) so I do need extended em.
cheers
On 19 April 2015 at 19:20, titou10 <[email protected]> wrote:
Le 2015-04-19 11:24, Mark Struberg a écrit :
Hi Dennis!
Have you *ever* hit this situation?
Yes, under heavy load it happens pretty often actually (I’m talking about
multi-million request/day public internet apps). It also depends a bit on
the JPA container you use. From the pure spec it is forbitten to touch the
EntityManager in parallel threads and also to touch managed (‚attached’)
entities in parallel threads. What JPA container are you using?
Here we are talking about one ONE EM per ONE CDI Conversation.
So you have applications with multi-million request/day concurrently in
one CDI Conversation that may lead *often* to a misuse of the EM ?
Impressive... How do you do that: Ajax requests? Proprietary client
javascript framework?
Or you are talking about *not closed EM* because the @PreDestroy callback
method has not been called in some particulat situation (sendRedirect is
called and the new request is processed before the initial request)?
Sorry, Mark but you lost me.....
Denis
Also, who programs a „sendRedirect" in the middle of a method that then
performs database access ..?
You don’t need to do database access even. It is enough that the
entitymanager is not closed as per the spec.
Even so, this is pure theory, the chance are so tiny this happens…
Then I had bad luck - quite often ;)
And If you think this *may* happen within one conversation, then change
the way redirects are send, or the way database is accessed in parallel in
Ajax requests. not the way EM is used IMHO
That might be a solution. Or force the EM to get closed before the
redirect.
Also your remark on „unfinished thread" is valid for ANY
components/resources held in ConversationScope, not just the EM, true?
Yes, but most components have no problems with getting accessed in
parallel. For managed Entities and EntityManagers it’s explicitly forbidden
by the JPA spec.
LieGrue,
strub
