public class JPAValidateListener {
   //No need for weakReference if the event listener is loaded by the same CL than
   //the entities, but in a shared env this is not the case
   //TODO check that this can be hot redeployable
   private static final Map<Class, WeakReference<ClassValidator>> validators;
   private static final ClassValidator<JPAValidateListener> NO_VALIDATOR;
   static {
      validators = new WeakHashMap<Class, WeakReference<ClassValidator>>();
      NO_VALIDATOR = new ClassValidator<JPAValidateListener>( JPAValidateListener.class);
   }

   //keep hardref at the instance level
   private final Set<ClassValidator> currentValidators = new HashSet<ClassValidator>();

   @PrePersist
   @PreUpdate
   @SuppressWarnings( "unchecked" )
   public void onChange(Object object) {
      if (object == null) return;
      Class entity = object.getClass();
      WeakReference<ClassValidator> weakValidator = validators.get(entity);
      ClassValidator validator = weakValidator != null ? weakValidator.get() : null;
      if ( validator == null ) {
         //initialize
         //TODO reuse the same reflection manager?
         validator = new ClassValidator(entity);
         if ( ! validator.hasValidationRules() ) {
            validator = NO_VALIDATOR;
         }
         validators.put( entity, new WeakReference<ClassValidator>(validator) );
         currentValidators.add( validator );
      }
      if ( validator != NO_VALIDATOR ) {
         validator.assertValid( object );
      }
   }
}