Re: [eclipselink-users] question about composite persistence unit

[Tom Ware <tom.ware@xxxxxxxxxx>]

Some comments inline:

On 03/03/2012 1:39 AM, Geronimo Ma. Hernandez wrote:
> Hello,
>
> On Friday 02 March 2012 - 19:03:48, Tom Ware wrote:
> > Lets take a step back.
> > ...
> > https://fisheye2.atlassian.com/browse/eclipselink/trunk/examples/my-sports/
> > MySports/src/example/mysports/admin/AdminMetadataSource.java?hb=true
> >
> > https://fisheye2.atlassian.com/browse/eclipselink/trunk/examples/my-sports/
> > MySports/src/example/mysports/admin/RESTAdminServerConnector.java?r=9600
>
> Thanks for the links.
>
> I probably was hobnailed describing my problem.
> I don't need Assistance on how to write a MetaDataSource. The point is, I
> don't know how to bring it into play.

The extended XML is used any time a new EntityManagerFactory is created or on a 
call to EntityManagerFactory.refreshMetadata() - that method is 
EclipseLink-specific, so you'll have to unwrap your factory to use it.

Note: The refreshMetadata() method is on EntityManagerFactory and not 
EntityManager.  If you are dynamically extending your entities, you won't be 
able to use the same EntityManager to operate on the extended entities. 
Instead, you call refreshMetadata() and from then on every EntityManager you 
obtain from the EntityManagerFactory will use the extended entities.  Previously 
created EntityManagers will use the old mappings.

> Anyway - after sessions of research and debug, I have to confess, that I was
> wrong on my last post:
>
> 	 I do need dynamic extension of known entities.
>
> The workflow of my app is like this:
> - authentication happens at splashscreen (no extension-plugin might have been
> loaded at that point)
>
> - application is loaded and navigation tree is shown (uses statically
> published entities from app core)
>
> - the user decides to expand a tree node, which triggers the activation of an
> extension plugin. That's the point, I have to inform the EntityManager about
> new classes, it should care about.
>
>
> Persistence (in my app) is an application service, coded in core app and
> published as a service - so all extensions will use the same application-
> session from authentication.
>
> I dived into the eclipselink sources and found a
> EntityManagerSetupImpl.updateDescriptorCacheSettings(...) - I know, that's
> internal stuff, but is there a way to trigger that call (or similar action)
> from application?

What is your goal in calling this method?

> I could imagine a Properties instance in my app, which gets extended by
> extension-plugin activation and for so always holds the pool of known entity-
> names.
> Binding that PropertyMap to a Handler of the EntityDescriptorCache, dynamic
> change of supported classes could be established.
>
> Don't know how weaving interferes this game, but using static weaving should
> make the binaries fit into dynamic play. Can I trigger weaving at build-
> process?

I'm not sure I understand the two paragraphs above.

> kind regards
>
> Gero
>
> P.S. digging the sources, I hit DatabaseSessionImpl - is it true, that in SE-
> environments only one database connection is supported/allowed?
> Before eclipselink, I was using connectionpool from apache.
> Is there a way to use connectionpools with eclipselink?

JPA applications and most enterprise applications tend to use ServerSession and 
ClientSession (rather than directly using DatabaseSessionImpl).  Connection 
pools are supported by server session.


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