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From David Jencks <>
Subject Re: [Discussion] JPA Pluggability
Date Tue, 05 Apr 2011 16:39:48 GMT
Hi Rex,

I too would like to know which parts of the spec cover this.

for (1), karaf already has a wrap deployer based (I think) on a pax project.  It uses bnd
under the covers and results in (I think) dynamic imports for all the packages used by the
wrapped jar.  We also need to be careful not to wrap something that is already a bundle. 
It may also be spec compliant to ask the server administrator to convert the jpa provider
jar(s) into bundles.  I really doubt the lib directory is mentioned in the spec.... if it
is the entire spec committee was asleep...

for (2), I think we should wait a few days.  In my private work on architecture I've eliminated
the dependencies in Environment.  With the possible exception of base classes related to enhancement,
I don't think the application actually needs access to the jpa provider classes.  Does anyone
know or can anyone figure out what provider imports are needed to make openjpa work?  Aries
might have solved this problem....

david jencks

On Apr 5, 2011, at 2:16 AM, Rex Wang wrote:

> HI Devs,
> These days I am looking into this new feature that we need implement to comply the Java
EE 6 Spec.
> This feature requires the ability to "plug-in" a vendor JPA Provider to the Java EE server,
and the JPA app can "pick-up" the vendor provider and get 
> the corresponding EntityManagerFactory. That is, let's take a use case for example, the
steps are:
> a. User put a Oracle topLink.jar into the server's lib folder.
> b. In the JPA app's persistence.xml, specify the provider as following:
>       <provider>oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider</provider>
> Then the entity manager factory should be created from the toplink's EntityManagerFactoryProvider
by our server.
> Currently, we don't have such ability because of the following obstacles:
> 1. We are running server on OSGi framework. There is not way to just put-in a jar file
and make it work for other Bundles' classloader. 
> 2. We are tight coupling the JPA20 builder to Openjpa. In the PersistenceUnitBuilder,
we set the defaultEnvironment with:
>                 <dependencies>
>                     <dependency>
>                         <groupId>org.apache.geronimo.configs</groupId>
>                         <artifactId>openjpa2</artifactId>
>                         <version>${version}</version>
>                         <type>car</type>
>                     </dependency>
>                 </dependencies>
>     This will add all the export-packages from openjpa to the JPA app bundle when deploy,
but it is actually useless for the ones specified other vendor providers.
> For #1, I think we should add the ability to convert a normal jar to OSGi bundle. I looked
into the maven-bundle-plugin, and the aQute bndlib should be a good tool to do this. We can
just provide the basic function that wrap a jar and:
>   Export-Package: * 
>   Import-Package: <packages inside the target jar>
> to make it as bundle. And in the long term, we can provide a portlet in admin console
for user to customizing his bundle.
> For #2, User need input the dependency in the jpa app's deployment plan and specify to
the bundle generated by geronimo in #1, such as:
>                 <dependencies>
>                     <dependency>
>                         <groupId>geronimo.generated.bundles</groupId>
>                         <artifactId>topLink</artifactId>
>                         <version>1.0</version>
>                         <type>jar</type>
>                     </dependency>
>                 </dependencies>
> Then all the topLink export-packages will be imported by the jpa app bundle of user.
We won't need merge the defaultEnviroment(i.e. openjpa) in the  PersistenceUnitBuilder if
use specify a vendor provider in persistence.xml. Another approach is we can add the imports
"oracle.toplink.essentials.ejb.cmp3;" when analyzing the persistence.xml in PersistenceUnitBuilder
so that user won't need manually add a deployment plan and input the dependency.
> Any comments?
> -- 
> Lei Wang (Rex)
> rwonly AT

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