EntityManager em = emf.createEntityManager();

        ClassDescriptor desc = ((EntityManagerImpl) em).getServerSession().getClassDescriptor(Kunde.class);
        desc.useFactoryInstantiationPolicy( KundeFactory.class,  "create2");

        em.getTransaction().begin();

  
private static synchronized  Map<Class<?>,Class<?>> loadDomainObjectMap( Session session ) {

        if( domainObjectMap != null )
            return domainObjectMap;

        Map<Class<?>,Class<?>> map = new HashMap<Class<?>, Class<?>>();

        for( Object e : session.getDescriptors().keySet() ) {
            Class<?> c = (Class<?>) e;

            String name = domainObjectPackage + c.getSimpleName() + "BO";

            try {
                Class<?> d = Tx.class.getClassLoader().loadClass(name);
                map.put(c, d);
            } catch( ClassNotFoundException ex ) {
            }

        }

        return domainObjectMap = map;
    }

    private static Map<Class<?>,Class<?>> getDomainObjectMap( Session session ) {
        if( domainObjectMap != null )
            return domainObjectMap;

        return loadDomainObjectMap(session);
    }

        
EntityManager em = emf.createEntityManager();
        
Session session = ((EntityManagerImpl) em).getActiveSession();
        
for( Map.Entry< Class<?>, Class<?> > e : getDomainObjectMap(session).entrySet() ) {

  ClassDescriptor desc = session.getClassDescriptor( e.getKey() );
  desc.setInstantiationPolicy( new InstantiationPolicy() );
  desc.setJavaClass( e.getValue() );

  session.getDescriptors().put( e.getValue(), desc );
}