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Posted to dev@openjpa.apache.org by "Hans J. Prueller" <ha...@gmx.net> on 2007/02/16 19:30:35 UTC
howto/pattern for working with three databases outside an EJB3 container
Hi there,
meanwhile I succeeded in getting OpenJPA to work within my J2EE 1.4
container and
I was able to replace a CMP entity bean by a JPA Pojo and perform basic
operations
on it (insert/persist, query).
The hi-lo table sequence generator works fine, so I can avoid conflicts with
existing
generated PKs already in the database.
Before I can start the real world migration I just want to clarify an
architectural question,
your ideas would be welcome:
- I am using OpenJPA is "the persistence engine of choice" now
within our Java2EE 1.4 application
- all new persistent entities will be created using JPA
- all existing CMP EBs will be migrated/replaced by JPA in a longer
process (step by step as this is very complex)
- the application runs on 3 databases, one for production data, a
repository of additional stuff and a statistics module
My question is:
How would the most efficient way look like to integrate OpenJPA with three
databases within our application (which - from the
JPA point of view - means outside a container).
I want to avoid to invoke
emFactory = Persistence.createEntityManagerFactory("lbsims");
EntityManager em2 = emFactory.createEntityManager();
.
every time I need to perform a query of something else. Somehow there should
be a Util-Class that provides already
created Factories for all three databases (e.g. persistence units) within my
application. I already thought about implementing
this within an abstract base class of all my persistent pojos - but I think
this isn't a beautiful solution. At least because it
means mixing technical code with my domain object model.
How are people approaching similar problems?
Any ideas are appreciated!
HANS
===========================
virtually hanzz...
<http://hanzz.zapto.org> http://hanzz.zapto.org (personal)
<http://www.cse.dmu.ac.uk/~hansp> http://www.cse.dmu.ac.uk/~hansp
(research)
RE: howto/pattern for working with three databases outside an EJB3 container
Posted by Patrick Linskey <pl...@bea.com>.
The problem is that the create* methods actually return new factories,
whereas the get* methods use OpenJPA's broker pooling.
-Patrick
--
Patrick Linskey
BEA Systems, Inc.
_______________________________________________________________________
Notice: This email message, together with any attachments, may contain
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and have received this message in error, please immediately return this
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> -----Original Message-----
> From: Don Brady [mailto:dbrady@pobox.com]
> Sent: Friday, February 16, 2007 10:51 AM
> To: open-jpa-dev@incubator.apache.org
> Subject: Re: howto/pattern for working with three databases
> outside an EJB3 container
>
> Patrick,
>
>
> Can the following not be used?
>
> createEntityManagerFactory(String name, String resource)
>
> Returns a new OpenJPAEntityManagerFactory specified by name in an XML
> configuration file at the resource location resource.
>
> Don
>
>
>
> Patrick Linskey wrote:
> > Hmm. Theoretically, this is what the
> > OpenJPAPersistence.getEntityManagerFactory() methods are there for.
> > However, looking at them, there is no way to specify your
> persistence
> > unit when using those methods. We should add those methods to
> > OpenJPAPersistence.
> >
> > Am I overlooking something in the implementation of those methods,
> > anyone?
> >
> > -Patrick
> >
>
>
Re: howto/pattern for working with three databases outside an EJB3
container
Posted by Don Brady <db...@pobox.com>.
Patrick,
Can the following not be used?
createEntityManagerFactory(String name, String resource)
Returns a new OpenJPAEntityManagerFactory specified by name in an XML
configuration file at the resource location resource.
Don
Patrick Linskey wrote:
> Hmm. Theoretically, this is what the
> OpenJPAPersistence.getEntityManagerFactory() methods are there for.
> However, looking at them, there is no way to specify your persistence
> unit when using those methods. We should add those methods to
> OpenJPAPersistence.
>
> Am I overlooking something in the implementation of those methods,
> anyone?
>
> -Patrick
>
RE: howto/pattern for working with three databases outside an EJB3 container
Posted by Patrick Linskey <pl...@bea.com>.
Hmm. Theoretically, this is what the
OpenJPAPersistence.getEntityManagerFactory() methods are there for.
However, looking at them, there is no way to specify your persistence
unit when using those methods. We should add those methods to
OpenJPAPersistence.
Am I overlooking something in the implementation of those methods,
anyone?
-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: Hans J. Prueller [mailto:hans.prueller@gmx.net]
> Sent: Friday, February 16, 2007 10:31 AM
> To: open-jpa-dev@incubator.apache.org
> Subject: howto/pattern for working with three databases
> outside an EJB3 container
>
> Hi there,
>
>
>
> meanwhile I succeeded in getting OpenJPA to work within my J2EE 1.4
> container and
>
> I was able to replace a CMP entity bean by a JPA Pojo and
> perform basic
> operations
>
> on it (insert/persist, query).
>
>
>
> The hi-lo table sequence generator works fine, so I can avoid
> conflicts with
> existing
>
> generated PKs already in the database.
>
>
>
> Before I can start the real world migration I just want to clarify an
> architectural question,
>
> your ideas would be welcome:
>
>
>
> - I am using OpenJPA is "the persistence engine of
> choice" now
> within our Java2EE 1.4 application
>
> - all new persistent entities will be created using JPA
>
> - all existing CMP EBs will be migrated/replaced by
> JPA in a longer
> process (step by step as this is very complex)
>
> - the application runs on 3 databases, one for
> production data, a
> repository of additional stuff and a statistics module
>
>
>
> My question is:
>
> How would the most efficient way look like to integrate
> OpenJPA with three
> databases within our application (which - from the
>
> JPA point of view - means outside a container).
>
>
>
> I want to avoid to invoke
>
>
>
> emFactory = Persistence.createEntityManagerFactory("lbsims");
>
> EntityManager em2 = emFactory.createEntityManager();
>
> .
>
>
>
> every time I need to perform a query of something else.
> Somehow there should
> be a Util-Class that provides already
>
> created Factories for all three databases (e.g. persistence
> units) within my
> application. I already thought about implementing
>
> this within an abstract base class of all my persistent pojos
> - but I think
> this isn't a beautiful solution. At least because it
>
> means mixing technical code with my domain object model.
>
>
>
> How are people approaching similar problems?
>
>
>
> Any ideas are appreciated!
>
>
>
> HANS
>
>
>
>
>
> ===========================
> virtually hanzz...
>
>
>
> <http://hanzz.zapto.org> http://hanzz.zapto.org (personal)
> <http://www.cse.dmu.ac.uk/~hansp> http://www.cse.dmu.ac.uk/~hansp
> (research)
>
>
>
>