Reload Hibernate3 EntityManagerFactory / SessionFactory after entity class definition/change.
Implementation notes:
The plugin hooks for initialization into org.hibernate.ejb.HibernatePersistence (for EJB 3.0) or
org.hibernate.cfg.Configuration (for plain Hibernate) to wrap javax.persistence.EntityManagerFactory or
org.hibernate.SessionFactory with a proxy. All clients then obtain reference for the proxy only.
Hibernte plugin listens for a change and hotswap on all classes on classpath. If the class contains
@javax.persistence.Entity annotation, whole Hibernate configuration is reloaded and target factory is
swapped in the proxy.
New EnityManager/SessionFactory instance is than obtained on next EnityManager.createEntityManager() call.
EntityManager created before reload remains unchanged.
HibernateTransformers registers static transformer for main Hibernate configuration class
org.hibernate.ejb.HibernatePersistence. The methods createEntityManagerFactory /
createContainerEntityManagerFactory are wrapped with a call to
HibernatePersistenceHelper.createContainerEntityManagerFactoryProxy, which creates a proxy and
registers the proxy in static context to be accessible for the reloading.
Plugin instance HibernatePlugin.entityReload() / HibernatePlugin.newEntity() then listen
for hotswap / new class file and schedules an HibernateRefreshCommands.reloadEntityManagerFactory()
command to run in the application classloader. This translates directly to invocation of
EntityManagerFactoryProxy.refreshProxiedFactories() which in turn calls refreshProxiedFactory() for
each registered factory. The refresh is similar to standard Hibernate new configuration loading mechanism
in org.hibernate.ejb.HibernatePersistence.
TODO:
- Check for all Hibernate annotations (not just Entity)
- Listen only on a package (not whole classpath) - probably hook somewhere in in the hibernate processing, because persistence.xml or .hbm.xml can be overridden by dynamic configuration (for example by Spring)
HibernatePlugin.entityReload- check if the class is an Entity can be resolved by Hibernate, not just the annotation.- Selective reload (because full reload is fast and very easy, this has low priority)
