Bean Validation is a good option to validate objects, but how to customize the response of a REST API (using RESTeasy) when a ConstraintViolationException is thrown?
For example:
@POST
@Path("company")
@Consumes("application/json")
public void saveCompany(@Valid Company company) {
...
}
A request with invalid data will return a HTTP 400 status code with the following body:
[PARAMETER]
[saveCompany.arg0.name]
[{company.name.size}]
[a]
It's nice but not enough, I would like to normalize these kind of errors in a JSON document.
How can I customize this behavior?
With JAX-RS can define an ExceptionMapper to handle ConstraintViolationExceptions.
From the ConstraintViolationException, you can get a set of ConstraintViolation, that exposes the constraint violation context, then map the details you need to an abitrary class and return in the response:
@Provider
public class ConstraintViolationExceptionMapper
implements ExceptionMapper<ConstraintViolationException> {
@Override
public Response toResponse(ConstraintViolationException exception) {
List<ValidationError> errors = exception.getConstraintViolations().stream()
.map(this::toValidationError)
.collect(Collectors.toList());
return Response.status(Response.Status.BAD_REQUEST).entity(errors)
.type(MediaType.APPLICATION_JSON).build();
}
private ValidationError toValidationError(ConstraintViolation constraintViolation) {
ValidationError error = new ValidationError();
error.setPath(constraintViolation.getPropertyPath().toString());
error.setMessage(constraintViolation.getMessage());
return error;
}
}
public class ValidationError {
private String path;
private String message;
// Getters and setters
}
If you use Jackson for JSON parsing, you may want to have a look at this answer, showing how to get the value of the actual JSON property.