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From Bengt Rodehav <be...@rodehav.com>
Subject Re: OSGi JPA and JDBC Services
Date Fri, 17 Sep 2010 10:10:18 GMT
Have I misunderstood when I use "aries:" instead of "osgi:" or is it just
different prefixes to the same namespace? In the JPA samples I cannot see in
the persistence descriptor what namespace "aries:" actually refers to.

/Bengt

2010/9/17 Timothy Ward <timothyjward@hotmail.com>

>
> Hi Harald,
>
> The Aries project aims to provide a managed programming model, and as such
> the Aries JPA runtime is not an implementation of the JPA service
> specification.
>
> As a result I'm afraid my first answer is no, Aries JPA cannot be used to
> get unmanaged JPA support, however if you declare your persistence units to
> use RESOURCE_LOCAL transactions then there shouldn't be a need for OpenJPA
> to load any JTA classes. Please let me know if OpenJPA continues to complain
> about the lack of JTA interfaces for RESOURCE_LOCAL persistence units and
> I'll try to get that fixed.
>
> For your requirements you should need two bundles from the Aries JPA
> project, the Aries JPA API bundle and the Aries JPA container bundle. You
> will also need the Aries Util bundle, which the JPA project uses.
>
> For reference, the JPA container bundles provide the following support:
>
> jpa-api               :- Core interfaces used by the Aries JPA runtime and
> Service providers
> jpa-container         :- The core JPA container, provides managed
> EntityManager factories for use in Application-Managed JPA
> jpa-container-context :- JPA managed persistence context support, allows
> for bundles to be registered as clients of a managed persistence context
> jpa-blueprint-aries   :- Integration with the aries blueprint service
> providing a custom namespace for JPA resource injection
>
>
> The Aries JPA container is loosely coupled, so it is entirely possible to
> pick the bundles you need for the support you want, though each piece of
> support builds upon the previous one, so it doesn't make much sense to have
> managed persistence context support without managed persistence unit
> support.
>
> There's no need to use blueprint, Declarative Services is perfectly capable
> of retrieving EntityManagerFactory services from the service registry.
>
> How data sources are discovered depends upon how they are configured, if
> you use the <jta-data-source> or <non-jta-data-source> tag, then the Aries
> JPA container will use JNDI to get the resource registered with that JNDI
> name. In most cases you actually want to access a DataSource object in the
> service registry, which means you need the Aries JNDI support (available as
> a single bundle, or as separate core and URL handler bundles) which provides
> the osgi: namespace.
>
> If you want to specify database driver class names in the <properties>
> section of the persistence unit then the JPA provider needs to be able to
> load those drivers. I do not know whether OpenJPA has support for the OSGi
> JDBC service specification, or whether they will simply try to load the
> driver classes, and so this may not work.
>
> I hope this message has been helpful, and I agree that there is
> insufficient documentation in this area. I would be more than happy for any
> Aries users to contribute information that they find useful so that better
> documentation can be built.
>
> Regards,
>
> Tim
>
> ----------------------------------------
> > From: Harald.Wellmann@multi-m.de
> > To: aries-user@incubator.apache.org
> > Date: Thu, 16 Sep 2010 20:31:48 +0200
> > Subject: OSGi JPA and JDBC Services
> >
> > I'm currently trying to make OpenJPA 2.0.1 work in an OSGi environment,
> and while looking for examples, I found a pointer to Apache Aries on the
> OpenJPA Users' mailing list.
> >
> > So I had a look at the Aries website, checked out the latest code from
> trunk, played around with it for a couple of hours and was left with no
> usable result - it sort of feels like being offered a four course meal when
> all you were asking for was a plate of soup, and you don't even get a
> spoon...
> >
> > All I want to do is use OpenJPA in plain old unmanaged mode and have it
> discover my persistence units and load classes from my application bundles
> without DynamicImport-Package, buddy policies or fragments. I am currently
> perfectly happy with Declarative Services and have no intention of
> converting my application to Blueprint.
> >
> > Can Aries be used to achieve just that? If so, what is the minimum set of
> Aries bundles I need to include in my application?
> >
> > I got as far as having my persistence unit discovered, but on creating an
> EntityManagerFactory, OpenJPA always complained about missing JTA support.
> Does Aries implement unmanaged JPA at all? (It is supported by the OSGi JPA
> spec, at any rate.) I can only see a call of
> PersistenceProvider.createContainerEntityManagerFactory() in Aries and no
> occurrence of createEntityManagerFactory(). On the OpenJPA side, there is
> some code related to OSGi classloaders, but again, this is just used for the
> managed factories and not for the unmanaged ones.
> >
> > Another question: how does the Persistence Provider discover the data
> source - where does the magic happen so that the lookup of
> osgi:service:/javax.sql.DataSource will work? Is that done by Aries alone,
> or does the persistence provider need to be OSGi aware in this respect?
> >
> > Thanks in advance for any hints!
> >
> > Best regards,
> > Harald
>
>

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