JSR 303 validation is not supported for REST methods. It would be nice if you could annotate a controller method with @Valid. This would validate the @RequestBody parameter and return 400 (bad request). If the resulting model contains invalid objects a 500 (internal server error) should be returned.
see http://blog.newsplore.com/2010/02/23/spring-mvc-3-0-rest-rebuttal "JSR 303 bean validation not applied in @Controllers"