[hibernate-dev] ServiceRegistries and OSGi

[Brett Meyer]

Alright, 3 week late response ;)

In hibernate-osgi, SF/EMF initialization simply uses the #with methods on BootstrapServiceRegistryBuilder, then builds a StandardServiceRegistry through the StandardServiceRegistryBuilder.  Originally, I was implementing a custom ServiceRegistry that hooked directly into the OSGi registry.  However, the consulting with Tim Ward changed that.  To prevent versioning conflicts, etc. hibernate-osgi only registers its own set of services and the services within the client persistence bundle (discovered when an SF/EMF is requested).  Because of that, I simply stuck with with the BootstrapServiceRegistryBuilder and StandardServiceRegistryBuilder.

It seems that the ServiceRegistry is a bit of an all-or-nothing concept.  For instance, it would be useful to provide a custom ServiceRegistry, but still kick off the StandardServiceInitiators.  Maybe that means tying StandardServiceInitiators into something more like an AbstractServiceRegistry, rather than solely within StandardServiceRegistryBuilder?  Otherwise, *all* standard services would need to be in the OSGi registry for hibernate-osgi to discover them.  That's fairly straightforward, but could cause problems if an OSGi environment had more than one version/instance of Hibernate running (it happens).

The one other improvement that I can think of is an easier way to provide a custom ServiceRegistry in JPA (Bootstrap -> EntityManagerFactoryBuilder).  Unless I missed something, I think it assumes the standard registry is always used.

Brett Meyer
Red Hat Software Engineer, Hibernate

----- Original Message -----
From: "Steve Ebersole" <steve at hibernate.org>
To: "hibernate-dev" <hibernate-dev at lists.jboss.org>
Sent: Wednesday, May 22, 2013 3:51:39 PM
Subject: [hibernate-dev] ServiceRegistries and OSGi

Now that OSGi support is in place and we know it is being used, I am 
curious whether the concept of ServiceRegistry helped or hindered in 
that process?

One of the major reasons to define such a ServiceRegistry was the idea 
that it would help porting Hibernate into other containers and other 
runtimes, not just traditonal JSE/JEE environments. Specifically OSGi 
was one of the things considered, although in a very generic sense back 
then.  So part  of the reason I ask is that I wonder how successful we 
were in that, first; and then, in areas we can get better, how?

Now is a great time to review that as we get ready to start making a 
push towards 5.0 after 4.3 (JPA 2.1 support) gets stabilized...
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