The relevant specification for learning about scoped resources (which is what
the ResourceProvider gives you) is the Transaction Control Specification. In
this case your question is covered by Section 147.2.5 Multi Threading
<https://osgi.org/specification/osgi.cmpn/7.0.0/service.transaction.control.html#d0e127038>.
Scoped resources are always thread safe and designed to be singleton objects
used across multiple scopes. The underlying scoped resource implementation then
delegates to a real resource instance that is bound to the current scope. The
result is that the real resource never sees multi-threaded access (a scope is
bound to a single thread) and that you never need to worry about
creating/closing the resource because the “real resource” is automatically
created (or retrieved from a pool) on first use within a scope and then closed
(or returned to the pool) when the scope finishes.
Best Regards,
Tim
> On 6 Feb 2019, at 22:14, Alex Soto <alex.s...@envieta.com> wrote:
>
> Actually, I took a stab at this again since I had some spare time now. I am
> almost done. It looks promising.
>
> The only question I have is about the entity manager. In the examples, I see
> an entity manager is obtained in the activate method, and used for the rest
> of the life of the component:
>
> private EntityManager em;
>
> @Activate
> void init() {
> em = provider.getResource(txControl);
> }
>
>
> Is this safe in a multi threaded environment? I expect the component to be
> called concurrently.
> Section 127.3.3 of OSGi Companion states that "An Entity Manager is intended
> to be used by a single session, it is not thread safe.” So I am confused
> since all examples seem to be ignoring this.
>
>
> Best regards,
> Alex soto
>
>
>
>
>> On Feb 6, 2019, at 3:16 PM, Tim Jones <t...@mccarthy.co.nz
>> <mailto:t...@mccarthy.co.nz>> wrote:
>>
>> Hi Alex,
>>
>> yes it is possible to use tx-control with Karaf, we have been using it on
>> v4.0.5 in our production system for about 18 months with no issues. One of
>> the main reasons we use tx-control is that is it 'backed' by a standard.
>> Rightly or wrongly we also didn't have confidence in Aries JPA Template at
>> the time we were considering transaction managment solutions to manage our
>> transactions in a production environment (perhaps this was misguided) but we
>> were concerned that there were few integrated tests for that project where
>> as there are over 2000 lines of test code for tx-control which demonstrate
>> sucess and failure cases for JPA, JDBC, non-XA, XA, last gambit wins,
>> commit, rollback depending upon exception type and much more.
>>
>> I think the enRoute project has some examples
>> https://enroute.osgi.org/examples/023-examples-microservice-jdbc.html
>> <https://enroute.osgi.org/examples/023-examples-microservice-jdbc.html> and
>> the tx-control test code is worth looking at.
>>
>> Tim
>>
>>
>>
>> --
>> Sent from: http://karaf.922171.n3.nabble.com/Karaf-User-f930749.html
>> <http://karaf.922171.n3.nabble.com/Karaf-User-f930749.html>
>
