public interface IDomainClassContributor {
	List<Class> getDomainClasses();
}

<bean id="sessionFactory" class="xxx.spring.ExtendableLocalSessionFactoryBean">
	   
   <property name="domainClassContributors">
      <osgi:set id="domainContributors" interface="xxx.spring.IDomainClassContributor" cardinality="0..N">
      </osgi:set>
   </property> 
		
   <property name="dataSource" ref="MYDataSource"/>
</bean>

private synchronized SessionFactory newExtendedSessionFactory(Configuration config) {
	ClassLoader cl = Thread.currentThread().getContextClassLoader();
	LoadContextClassLoaderProxy lccl = new LoadContextClassLoaderProxy(cl);
	Thread.currentThread().setContextClassLoader(lccl);
	if (domainContributors!=null)
	{
		for (IDomainClassContributor contributor: domainContributors)
		{
			List<Class> classes = contributor.getDomainClasses();
			for (Class clss: classes)
			{
				lccl.addLookupEntry(clss);
				config.addClass(clss);
			}
		}
	}
			
	SessionFactory factory = super.newSessionFactory(config);

	Thread.currentThread().setContextClassLoader(cl);
	
	return factory;
}

FrameworkUtil.getBundle(this.getClass()).getBundleContext().addServiceListener(new ServiceListener() {
				
   @Override
   public void serviceChanged(ServiceEvent arg0) {
   try {
      // This creates a new Configuration and a new SessionFacade
      afterPropertiesSet();
   } catch (Exception e) {
      e.printStackTrace();
   }
}
}, "("+Constants.OBJECTCLASS+"="+IDomainClassContributor.class.getName()+")");

@Override
protected synchronized SessionFactory newSessionFactory(Configuration config)
		throws HibernateException {

	extendedSessionFactory = newExtendedSessionFactory(config);
			
	/*
	 * Add a proxy to ensure that all accesses to the SessionFactory use the current extendedSessionFactory
	 */
	SessionFactory proxiedFactory = (SessionFactory) Proxy.newProxyInstance(getClass().getClassLoader(), 
			new Class[]{SessionFactory.class}, new InvocationHandler() {
				
				@Override
				public Object invoke(Object proxy, Method method, Object[] args)
						throws Throwable {
					return method.invoke(getExtendedSessionFactory(), args);
				}
			});
	return proxiedFactory;
}