Resteasy ExceptionMapper returning no result

Question

I am developing a REST-facade for an EJB service, which means it calls the EJB, translates the result to representations a REST-caller will understand and then returns it (as json or xml). All of that works splendid. But the EJB service throws a variety of exceptions, e. g. when no result is found or a few different other cases. Since I don't want those propagating to the REST-caller, I implemented an ExceptionMapper:

public class EjbExceptionMapper implements ExceptionMapper<EJBException> {

    private static final Logger logger = LoggerFactory.getLogger(EjbExceptionMapper.class);

    @Override
    public Response toResponse(final EJBException exception) {
        ResponseBuilder result = Response.status(Status.BAD_REQUEST);
        logger.debug("Bad request:", exception);
        if (exception.getCause() != null) {
            final Throwable cause = exception.getCause();
            if (cause instanceof NoDeliveryFoundException) {
                logger.debug("Found NoDeliveryFoundException:", cause);
                result = Response.status(Status.NO_CONTENT).entity(cause.getMessage());
            }
        }
        return result.build();
    }
}

All the exceptions from my EJB-service arrive as javax.ejb.EJBException, which this Mapper manages to catch just fine, with different custom Exceptions of the application as causes. The plan is to return different Responses depending on the type of cause of the EJBException. The logger-calls used for debugging are both executed in case I get a NoDeliveryFoundException as the cause, so I know it's executed (the Mapper registered correctly and is used for mapping), but the client never sees a response.

Every call leading to an EJBException in the underlying service (and thus the use of this ExceptionMapper) leads to no Response at all, as if the toResponse()-method were returning null and not a custom built Response.

I even went so far as to log the Response right before returning it, it exists and contains what I expect, so I am positive that it is returned by the toResponse-method. But still, my client receives no Response.

So now I'm stumped and since no search managed to even find someone describing a similar problem, I turn to you, dear SO. ;)

eiden eiden · Accepted Answer · 2013-09-22T09:21:07

Your toResponse-method contains some conflicting logic.

Response.status(Status.NO_CONTENT).entity(cause.getMessage());

Here you are assigning the the HTTP status code 204 No Content, but you are also adding a response. You can't set the status to 204 No Content and return a response body at the same time.

Also, if Exception#getCause() is null or if it's not an instance of NoDeliveryFoundException, the response body is empty.

Could this be the cause of your problems?

Resteasy ExceptionMapper returning no result

1 Answers