In my application I would like to use a particular error entity in the response message whenever a Bean Validation constraint is violated. Currently RestEasy provides its on error entity, which is ViolationReport, but I want to use my own instead. According to the Bean Validation 1.1 spec, a ConstraintViolationException should be thrown by the validator whenever a constraint is violated, in a JAX-RS scenario one could handle them by having a ExceptionMapper mapping that exact exception. So, I did so, I added my own ExceptionMapper mapping ConstraintViolationException, but I realized that does not work as expected because RestEasy, as the bean validator (together with Hibernate Bean Validation implementation), never throws a ConstraintViolationException when a constraint is violated. Instead of that RestEasy throws its own proprietary exception, which is ResteasyViolationException. If ResteasyViolationException was a subclass of ConstraintViolationException then maybe my ExceptionMapper would work, and that is because there is not any exception mapper mapping ResteasyViolationException directly. RestEasy instead maps ValidationException (in ResteasyViolationExceptionMapper), and then figure outs the specific type of exception within it. JAX-RS states that a JAX-RS implementation must have an exception mapper for ValidationException, which is the super type of ConstraintViolationException. So, in that regard RestEasy is good. However, RestEasy violates Bean Validation when it throws its own exception type, instead of ConstraintViolationException, when a constraint is violated. And, because of that, I cannot deal with that by myself (and change the error entity as I want).

Here is where the problem is: https://github.com/resteasy/Resteasy/blob/3.0.9.Final/jaxrs/providers/resteasy-validator-provider-11/src/main/java/org/jboss/resteasy/plugins/validation/GeneralValidatorImpl.java#L185

Possible solution:
That ResteasyViolationException could be a subclass of ConstraintViolationException.