Jim,
From your reply, I think the key is injecting in a persistence unit.
Hibernate has an EJB 3.0 implementation (both the OR annotations and the
entity manager). This will work pretty much the same as open JPA (or any
closed JPA :-), sorry couldn't resist it)
May be we can have a framework that can support any JPA implementation make
the EMF available as a system service.
Ta
Meeraj
From: Jim Marino <[EMAIL PROTECTED]>
Reply-To: [email protected]
To: [email protected]
Subject: Re: EJB3 (JPA) support
Date: Mon, 2 Oct 2006 10:30:20 -0700
Sure (since both you and Meeraj asked)...
Basically, I think the use cases are pretty much the same for JPA,
Hibernate, or JDO (not surprisingly): an application developer wants to
use a strongly-typed O/R mapper to persist data used within a service or
composite implementation. They should be able to use any of the JPA
annotations to inject an entity manager onto a service instance:
public class FooImpl extends Foo {
@PersistenceUnit(name="example")
protected EntityManager entityManager;
}
Hibernate would work the same way, except inject a Session. This would
basically be an example of the "layering" approach to Java C&I that we
have discussed in the spec group. Under the covers, Tuscany is managing
instances of EntityManagerFactory as system services and there is an
annotation extension which is responsible for performing the injection of
EntityManager instances (non-thread-safe) onto component implementation
instances.
I would expect developers to use this approach when:
- writing in Java or perhaps a "Java-friendly" language such as Groovy
(obviously!)
- they don't need to perform batch-oriented operations (JDBC is better for
that)
- they want to manipulate data in an O-O fashion as opposed to in a
loosely typed way or something like active record
- they don't want to use declarative services, or they are not suited for
an application's needs
- they just like JPA or Hibernate for whatever reason
From a non-technical perspective, this helps to embrace several
communities by showing how their technologies are relevant in an SCA
environment.
Jim
On Oct 2, 2006, at 8:00 AM, scabooz wrote:
Hi Jim,
This is the first time I've seen this topic discussed on the list.
Apologies
if I've missed it previously. Can you illuminate some of your
thinking behind it? I'm interested in understanding the use cases you
might be thinking of supporting, from at least the
perspective of the app developer.
thanks
Dave Booz
----- Original Message ----- From: "Jim Marino" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, October 02, 2006 3:24 AM
Subject: EJB3 (JPA) support
Hi,
I checked in a skeleton of EJB3 persistence support (using OpenJPA)
that will leverage the system service work I just did. If anyone is
interested in helping with this or adding in Hibernate support let me
know. We may want to look at providing a generic EJB3 JPA extension,
although I'm not sure how much common code would exist across
implementations.
Jim
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