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From Jeff Yu <jeff.yuch...@gmail.com>
Subject Ode DAO Impl status (Hibernate, OpenJPA, MemImpl)
Date Mon, 16 Nov 2009 08:03:05 GMT
Hi all,

I looked into our Ode DAO impl , it has three implementations at the moment,
one is Hibernate, one is Memdao, which I thought it is meant to be used in
test environment, the other one is JPA, but it ties to openJPA somehow, as
it uses the some OpenJPA API directly in the implementation.

Searched the 'hibernate openjpa' keyword in our maillist, only found this
thread(http://ode.markmail.org/message/mjqsz6ehykpzbons), which is back in
Dec, 2008.  Little info about these info. Well, I am trying to deploy Ode
with hibernate as JPA provider. But I learnt from an email that we may drop
hibernate implementation in the future, is this still the case? If so, I
guess we won't provide the migration tool for users from 1.3.x to 2.x
version. Will we provide a migration tool from the hibernate -> openjpa?

One thing that I didn't fully understand is that we've already tried to use
the JPA as our second level of abstraction for the DAO, (the first level
abstraction I see is our DAO interface), but I see we tied this impl into
OpenJPA by using following classes.

import org.apache.openjpa.ee.ManagedRuntime;
import org.apache.openjpa.util.GeneralException;

import org.apache.openjpa.persistence.OpenJPAPersistence;
import org.apache.openjpa.persistence.OpenJPAQuery;

It would be great that we can abstract these classes out from our jpa
module, so that openjpa and hibernate can have its own impl. I understand
the generated schema is pretty different in the openjpa and hibernate, but
they are transparent to users/developers. I meant, as long as they are using
the right combination (Hibernate + hibernate generated schema, or OpenJPA +
OpenJPA generated schema), they should be fine.

I've noticed that in the hibernate implementation, it is using the hibernate
specifc annotation, which seems to me that it hasn't been actively developed
for a long time.

I'd like to see us using the JPA in its impl, and can be deployed in any JPA
provider, in this case, it would be easy for users to deploy ode into any
JEE application server. I didn't know whats our plan for our DAO impl, both
for the 1.3.x and 2.0 version.  Also, some background on this and some
issues that we've had in the implementation would be of great helpful to me.

Thanks
Jeff

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