Re: Entity manager injection

[Craig L Russell]

Hi Matthew,








Craig

On Mar 5, 2007, at 9:28 AM, Matthieu Riou wrote:

Basically, with JPA we have formalized separation of concerns between the user's Domain Object Model, represented by Entity, and the user's Business Object, represented by Session Beans. There is no need for managing an EntityManager from the Entity itself. So you should simply remove references to the em in your Entity classes, and put them instead into your Session Beans. So injection doesn't work at all for Entity, but works for Session Beans.

Hmm. I believe that you actually fall into the first category -- OpenJPA only uses the ManagedRuntime when it thinks that it's integrating with

JTA. It sounds like you're using JTA to control transactions, and

plugging into OpenJPA SPIs to tell OpenJPA about how to bind into JTA.

manager is null when I use:

@Entity
public class Foo {
  @PersistenceContext private EntityManager em;
  ...
}

I see, so if what JPA needs is just a JTA transaction then yes we're in that category. So I guess the next question is do you have an idea why my entity ?? These 3 links point to the place we initialize the EM factory, the EM and a the persistence object that uses the EM and would like to use injection: http://svn.apache.org/repos/asf/incubator/ode/trunk/dao-jpa/src/ main/java/org/apache/ode/dao/jpa/BPELDAOConnectionFactoryImpl.java http://svn.apache.org/repos/asf/incubator/ode/trunk/dao-jpa/src/ main/java/org/apache/ode/dao/jpa/BPELDAOConnectionImpl.java http://svn.apache.org/repos/asf/incubator/ode/trunk/dao-jpa/src/ main/java/org/apache/ode/dao/jpa/ProcessDAOImpl.java

The hooks certainly do exist, for the most part. However, we already

have an API-based way to do this --
OpenJPAPersistence.getEntityManager(Object). Since injecting an
instance's EntityManager not quite the same as what happens with the
@PersistenceContext annotation from a Java EE standpoint, I prefer to
recommend the proprietary OpenJPA extension API. This makes it more

any semantic confusion.

clear where you are depending on OpenJPA-specific features, and avoids

Makes sense.

Thanks!
Matthieu

-Patrick

--
Patrick Linskey
BEA Systems, Inc.


by email and then delete it.

> -----Original Message-----
> From: Matthieu Riou [mailto:[EMAIL PROTECTED]
> Sent: Monday, March 05, 2007 8:48 AM
> To: Patrick Linskey
> Cc: open-jpa-dev@incubator.apache.org
> Subject: Re: Entity manager injection
>
> We're managing our own transactions using our
> TransactionManager provided through "openjpa.ManagedRuntime".
> So I guess we'll have to go for your second solution. I'll
> probably implement a simple ThreadLocal holding the
> EntityManager associated with the current tx.
>
> Btw it's just an idea but wouldn't it be possible for OpenJPA
> to handle persistence manager injection even outside of an
> EJB container? It seems to me that all the necessary hooks
> exist. Just an idea though :)
>
> Thanks for the help,
> Matthieu
>
>
> On 3/5/07, Patrick Linskey <[EMAIL PROTECTED]> wrote:
>
>       Hi,
>
>       IIRC, you're doing something like so:
>
>       @Entity
>       public class Foo {
>           @PersistenceContext private EntityManager em;
>           ...
>       }
>
>       The Java EE spec's support for resource injection does
> not apply for
>       entity types. So, from an EJB standpoint, you can only
> use resource
>       injection in session beans and MDBs. You're getting the
> NPE because your
>       EJB container ignores the @PersistenceContext
> annotation on your entity.
>       (Note that OpenJPA doesn't do anything at all with
> @PersistenceContext
>       annotations.)
>
>       If you were using a session bean, then there are two
> possible answers to
>       your question:
>
>       1. If you are managing your own transactions using JTA
> and bean-managed
>       transactions, then you'd be in good shape using
> @PersistenceContext.
>
>       2. If you are managing your own transactions using the JPA
>       EntityTransaction API, then you cannot use
> @PersistenceContext to inject
>       an EM, but instead must use @PersistenceUnit to inject an
>       EntityManagerFactory (or some other EMF lookup means),
> and do your own
>       lifecycle management.
>
>       -Patrick
>
>       --
>       Patrick Linskey
>       BEA Systems, Inc.
>
>
> ______________________________________________________________
> _________
>       Notice:  This email message, together with any
> attachments, may contain
>       information  of  BEA Systems,  Inc.,  its subsidiaries
> and  affiliated
>       entities,  that may be confidential,  proprietary,
> copyrighted  and/or
>       legally privileged, and is intended solely for the use
> of the individual
>       or entity named in this message. If you are not the
> intended recipient,
>       and have received this message in error, please
> immediately return this
>       by email and then delete it.
>
>       > -----Original Message-----
>       > From: Matthieu Riou [mailto: [EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]> ]
>       > Sent: Friday, March 02, 2007 8:32 AM
>       > To: open-jpa-dev@incubator.apache.org
>       > Subject: Entity manager injection
>       >
>       > Hi,
>       >
>       > For ODE we're managing our transactions ourselves. We start
>       > them and commit
>       > them explicitly. By the same token we create the
> EntityManagerFactory
>       > ourselves. Is there a possibility to use the EntityManager
>       > injection in the
>       > persistent classes in this context or do we have to
> implement our own
>       > ThreadLocal based thingy to have the EM available in our
>       > persistent classes
>       > using it?
>       >
>       > I've tried doing something like:
>       >
>       > 1. Adding "@PersistenceContext  private EntityManager _em;"
>       > in a persistence
>       > class.
>       > 2. Load the persistence class from an EntityManager
> created with the
>       > factory.
>       > 3. Use _em in my persistent class
>       >        => NullPointerException
>       >
>       > Thanks,
>       > Matthieu
>       >
>
>
>
>

_____________________________________________________________________ __ Notice: This email message, together with any attachments, may contain information of BEA Systems, Inc., its subsidiaries and affiliated entities, that may be confidential, proprietary, copyrighted and/or legally privileged, and is intended solely for the use of the individual or entity named in this message. If you are not the intended recipient, and have received this message in error, please immediately return this

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

smime.p7s
Description: S/MIME cryptographic signature