CC'ing hibernate-dev...
----- Original Message -----
> From: "Gail Badner" <gbad...@redhat.com>
> To: "Steve Ebersole" <st...@hibernate.org>, "Emmanuel Bernard"
> <emman...@hibernate.org>
> Sent: Friday, June 20, 2014 4:25:56 PM
> Subject: Overriding JpaMergeEventListener with
> JpaEntityCopyAllowedMergeEventListener
>
> I am trying into figure out how to override JpaMergeEventListener with
> JpaEntityCopyAllowedMergeEventListener as described in [1]. This
> documentation does not describe how to deal with injecting CallbackRegistry
> into an overridden MergeEventListener.
>
> CallbackRegistry is an SPI, but JpaMergeEventListener and
> CallbackRegistryConsumer are internal.
> JpaEntityCopyAllowedMergeEventListener is also internal.
>
> I was planning to document MyIntegrator.integrate(..) for enabling entity
> copies, but I don't like the idea of documenting an internal event listener
> for that functionality.
>
> Here is one alternative that minimizes exposing private classes/methods:
>
> public class MyIntegrator implements org.hibernate.integrator.spi.Integrator
> {
>
> public void integrate(
> Configuration configuration,
> SessionFactoryImplementor sessionFactory,
> SessionFactoryServiceRegistry serviceRegistry) {
> final EventListenerRegistry eventListenerRegistry =
> serviceRegistry.getService( EventListenerRegistry.class );
> final MergeEventListener mergeEventListener =
> mergeEventListenerGroup.listeners().iterator().next();
> final JpaEntityCopyAllowedMergeEventListener
> entityCopyAllowedMergeEventListener =
> new JpaEntityCopyAllowedMergeEventListener();
> entityCopyAllowedMergeEventListener.initializeFrom(
> mergeEventListener );
> registry.setListeners( EventType.MERGE,
> entityCopyAllowedMergeEventListener );
> }
> ...
> }
>
> public class JpaEntityCopyAllowedMergeEventListener extends
> JpaMergeEventListener {
> ...
> public void initializeFrom(MergeEventListener mergeEventListener) {
> if ( JpaMergeEventListener.class.isInstance( mergeEventListener ) ) {
> injectCallbackRegistryFrom( (JpaMergeEventListener)
> mergeEventListener );
> }
> }
> ...
> }
>
> public class JpaMergeEventListener extends DefaultMergeEventListener
> implements CallbackRegistryConsumer {
> ...
> protected void injectCallbackRegistryFrom(JpaMergeEventListener
> jpaMergeEventListener) {
> injectCallbackRegistry( jpaMergeEventListener.callbackRegistry );
> }
> ...
> }
>
> Another alternative is to change JpaEntityCopyAllowedMergeEventListener to be
> a Proxy that holds an instance of the original JpaMergeEventListener.
> Everything except for createEntityCopyObserver() could be delegated to the
> stored JpaMergeEventListener. There would be no need to call
> injectCallbackRegistry(CallBackRegistry).
>
> It might be possible to have one Proxy for
> JpaEntityCopyAllowedMergeEventListener and
> EntityCopyAllowedMergeEventListener holding an instance of
> MergeEventListener, but that Proxy wouldn't implement
> CallbackRegistryConsumer or HibernateEntityManagerEventListener. Does that
> matter for an overridden event listener if the CallbackRegistry does not
> have to be injected?
>
> Is there some other way of doing this that I've missed?
>
> Thanks,
> Gail
>
> [1]
> http://docs.jboss.org/hibernate/orm/4.3/devguide/en-US/html/ch07.html#registering-listeners-example
>
>
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