Question

I currently have a RESTful webservice running Jersey. I recently added a filter that does some auth stuff, and it works in the happy-path case. However, when I need to throw an error from within this filter, instead of serializing the exception into a pretty json string it, it throws a 500 with the following error:

javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: A message
body writer for Java class myclass, and Java type class myclass, and MIME media type
application/octet-stream was not found

The thing is, I don’t want to write anything to application/octet-stream. My service only uses application/json. This is not a problem in my actual Resource classes, where I can specify the@Produces annotation. Error responses thrown from the body of a resource will serialize properly.

My question, then, is: How do I control what MIME type is used for exceptions thrown while filtering?

Answer 1

You need to build an exceptionmapper to handle the exceptions and turn them in to JSON. Something like:

@Provider
public class UnexpectedExceptionMapper implements ExceptionMapper<Exception>
{
  @Override
  public Response toResponse(final Exception exception)
  {
    ResponseBuilder builder = Response.status(Status.BAD_REQUEST)
                                      .entity(jsonError(exception))
                                      .type(MediaType.APPLICATION_JSON);
    return builder.build();
  }

  private String jsonError(final Exception exception)
  {
    return "{\"error\":\"" + exception.getMessage() + "\"}";
  }
}