Hi Andriy, many thanks, I've applied your patch with few minor updates (example, JAXRSInvoker would always return MessageContentsList, plus few other minor updates).
What I've realized, though I guess we did touch on it earlier, is that if we have JAX-RS Response wrapping an entity then the only thing we can do at the moment is to validate a non-null entity itself, assuming it has the embedded constraints, but we always miss on method-level annotations such as @NotNull.
When we have a null Response entity we can check if method annotations have @NotNull and if yes then return a custom NotNulConstraintViolation. Thus we can cover the NotNull validation at least. But I wonder if we can do better than that ? Have a look please at ValidatorProvider#validateResponse(Method m, Object returnV), can we iterate over all the method annotations, check for the ones with Constraints, if yes, then invoke the attached ConstraintValidator. Can that work at all ? It is not a critical issue, if it is not possible to do then I can add a NotNull check only and then resolve this issue