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Date: Fri, 17 Sep 2010 09:49:48 -0700
Message-ID: <AANLkTinHAHgTiObr8PxfS=Lg6waTEowKL97WrPwpnJxW@mail.gmail.com>
Subject: Re: OSGi JPA and JDBC Services
From: Alasdair Nottingham <not@apache.org>
To: aries-user@incubator.apache.org
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Hi, you are right about the samples, it is on my todo list, but I
haven't got to it yet.

I've written some documentation as a result of your email. It isn't on
our website yet, it needs to sync from the wiki, but you can view it
here: https://cwiki.apache.org/confluence/display/ARIES/JNDIProject

Alasdair

On 17 September 2010 07:45, Bengt Rodehav <bengt@rodehav.com> wrote:
> Thanks for the clarification Alasdair,
> Are there any samples/examples of "osgi:" I can look at. Do I need to add=
 a
> namespace in the persistent descriptor, deploy certain bundles etc?
> Clearly, the way you describe it, "osgi:" must be preferred to "aries:".
> Maybe the Aries samples should change to reflect that?
> /Bengt
>
> 2010/9/17 Alasdair Nottingham <not@apache.org>
>>
>> aries:services is also a JNDI lookup scheme, it works much the same way =
as
>> osgi:service, but osgi:service returns a proxy to the target object whic=
h
>> switches out the target if it changes. aries:services does not proxy, yo=
u
>> get e raw object so it is a little bit less dynamic and safe.
>>
>> Alasdair Nottingham
>> On 17 Sep 2010, at 03:10, Bengt Rodehav <bengt@rodehav.com> wrote:
>>
>> Have I misunderstood when I use "aries:" instead of "osgi:" or is it jus=
t
>> different prefixes to the same namespace? In the JPA samples I cannot se=
e 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 unit=
s to
>>> use RESOURCE_LOCAL transactions then there shouldn't be a need for Open=
JPA
>>> to load any JTA classes. Please let me know if OpenJPA continues to com=
plain
>>> about the lack of JTA interfaces for RESOURCE_LOCAL persistence units a=
nd
>>> 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. Y=
ou
>>> will also need the Aries Util bundle, which the JPA project uses.
>>>
>>> For reference, the JPA container bundles provide the following support:
>>>
>>> jpa-api=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 :- Core interfaces us=
ed by the Aries JPA runtime
>>> and Service providers
>>> jpa-container=A0=A0=A0=A0=A0=A0=A0=A0 :- The core JPA container, provid=
es managed
>>> EntityManager factories for use in Application-Managed JPA
>>> jpa-container-context :- JPA managed persistence context support, allow=
s
>>> for bundles to be registered as clients of a managed persistence contex=
t
>>> jpa-blueprint-aries=A0=A0 :- Integration with the aries blueprint servi=
ce
>>> 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 o=
f
>>> 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, i=
f
>>> you use the <jta-data-source> or <non-jta-data-source> tag, then the Ar=
ies
>>> JPA container will use JNDI to get the resource registered with that JN=
DI
>>> name. In most cases you actually want to access a DataSource object in =
the
>>> service registry, which means you need the Aries JNDI support (availabl=
e as
>>> a single bundle, or as separate core and URL handler bundles) which pro=
vides
>>> 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 O=
SGi
>>> 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 bet=
ter
>>> 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 environmen=
t,
>>> > 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 fro=
m
>>> > 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 mea=
l 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 bu=
ndles
>>> > without DynamicImport-Package, buddy policies or fragments. I am curr=
ently
>>> > 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 se=
t
>>> > of Aries bundles I need to include in my application?
>>> >
>>> > I got as far as having my persistence unit discovered, but on creatin=
g
>>> > 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 an=
d no
>>> > occurrence of createEntityManagerFactory(). On the OpenJPA side, ther=
e 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 a=
lone,
>>> > or does the persistence provider need to be OSGi aware in this respec=
t?
>>> >
>>> > Thanks in advance for any hints!
>>> >
>>> > Best regards,
>>> > Harald
>>>
>
>


--=20
Alasdair Nottingham
not@apache.org