Hi Meeraj,
I checked in some minor changes to the JPA extension. I was thinking
things would work along the following lines:
- An application developer could specify a JPA persistence context in
their assembly using an <import.jpa name="">.
- JPAImportLoader would process <import.jpa> and resolve JPA
artifacts (persistence.xml, mapping files, etc.). It may need the
composite classloader to do this or come up with a better mechanism
(I'm too tired to really think about it now). JPAImportLoader would
also create an model of a JPA system service which would be used by
constructed by JPAComponentBuilder to create a JPAAtomicComponent.
The builder would register this system service in the parent
(application composite) tree.
- There would be an EntityManagerProcessor registered in the
*runtime* (as opposed to the application) system tree. When a user
component marked with @PersistenceContext is encountered,
EntityManagerProcessor would create a property and populate the
component type. the property would have a EntityManagerObjectFactory
which is responsible for injecting entity managers on the
implementation instance. EntityManagerProcessor would call
resolveSystemInstance() on the parent application composite and get
the EMF, passing it to an EntityManagerObjectFactory. The latter
would then be set as the default object factory on the property.
- When the user component is instantiated, the
EntityManagerObjectFactory will call to the EMF and create an
EntityManager.
I started skeleton work to support this but most of the hard stuff is
missing. For example, I believe we are going to need to figure out
dependency classloading as both the runtime system
EntityManagerProcessor and application components need access to JPA
classes. I probably haven't explained this very well, but maybe you
could take a look at the skeletal code and we could go from there?
I definitely think we should draw inspiration from what Spring did in
terms of integration. For example, we will probably need to figure
out how to support persistence contexts that span more than a
transaction. Once we get a basic working extension, we may want to
look at plugging this into a transaction manager, which we'll need
for policy support.
Jim
On Oct 2, 2006, at 11:51 PM, Meeraj Kunnumpurath wrote:
I will take a look Jim and try to assist, I have been doing a bit
recently at work with Hibernate JPA and the Spring 2.0 JPA support.
May
be we can draw some inspiration from Spring 2.0 as well.
Ta
-----Original Message-----
From: Jim Marino [mailto:[EMAIL PROTECTED]
Sent: 03 October 2006 07:46
To: [email protected]
Subject: Re: EJB3 (JPA) support
Yep. I'm working on some minor things to the JPA extension now and I
should have them checked in soon (hour or so). I'm still figuring out
how this stuff is going to work (I'm more familiar with the Hibernate
API than JPA) but perhaps when I do the check in I can send another
note
describing the changes and you can have a look to see if it makes
sense,
and maybe take it forward a bit? I think the Hibernate API one should
work similarly.
Jim
On Oct 2, 2006, at 11:36 PM, Meeraj Kunnumpurath wrote:
Do you mean the Hibernate session API without using the entity
manager?
-----Original Message-----
From: Jim Marino [mailto:[EMAIL PROTECTED]
Sent: 02 October 2006 20:30
To: [email protected]
Subject: Re: EJB3 (JPA) support
On Oct 2, 2006, at 11:35 AM, Meeraj Kunnumpurath wrote:
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)
Yes I think we want to have a generic integration if possible so we
can use ClosedJPA too ;-) There may be some customizations we need
for
particular vendor impls.
May be we can have a framework that can support any JPA
implementation
make the EMF available as a system service.
Yes agreed, although we may not want to say "EMF" since that may
confuse people with Eclipse Modeling Framework :-) I'd also like to
get a Hibernate integration going for people that like that API.
Jim
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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