[cdi-dev] CDI 2.0 EDR: Questions on asynchronous observers

[Jozef Hartinger]

On 11.8.2015 17:33, Nigel Deakin wrote:
> I've read section 10 "Events" of the CDI 2.0 early draft, and have a couple of quick questions about asynchronous
> observers.
>
> I'd like to understand how these work with transactions. (I'm referring to normal observer methods here, not the rather
> specialised "transactional observer methods")
>
> 10.5 states "...An observer method may not directly initiate, commit or rollback JTA transactions."
>
> This wording is unchanged from CDI 1.1. What is the reason for this restriction? I think it might be useful if an
> observer method was able to use the JTA API to start and end a transaction, especially when the observer method is being
> called asynchronously.

I think this is just an oversight and this statement was not updated in 
the light of CDI 2.0 (although it should have).

>
> 10.5.3 "If the observer method is asynchronous, it is called in... a new transaction context...".
>
> What does "a new transaction context" mean? Does this mean that the container will start a transaction before calling
> the observer method? If so, it would be useful if the application could disable this. If not, it would be useful if the
> application could itself use the JTA API to start and end a transaction.

I think that what this statement is trying to say is simply that the 
transactional context of the event sender is not propagated to the async 
observer.

The observer should IMO be able to work with the transactional context 
using EJB managed transactions, @Transactional or manually with 
UserTransaction.

>
> Nigel
>
>
>
>
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