Given an EJB that extends no interface (uses the no-interface view variant of EJB3.1), any validation annotation put on any parameter on any public method is automatically added to the proxy of that ejb created by the container.
At this moment, hibernate validator complains saying:
Only the root method of an overridden method in an inheritance hierarchy may be annotated with parameter constraints, but there are parameter constraints defined at all of the following overridden methods...
The methods signalled are: the one from the ejb and the one from the proxy.
There is obviously no way around it but to declare an interface for that EJB and move the validation annotations there. An ugly workaround.