spring boot (mvc) response with different content type encoding on error - rest

Question

I need help with spring handling an error.
a client service is sending a request accepting two different content types - binary and json. when everything works fine I prefer communicating to my server with binary encoding to save bandwidth. but on error I would like serialise ResponseEntity to json as my binary serialiser do not know how to serialise it to binary format, plus it is better for logging, etc.
I configured instance of ResponseEntityExceptionHandler and I am handling different exceptions from that implementation. but spring always choses binary format as it is first on the accept (or produces) list.
all I get is (because spring do not know how to serialise ResponseEntity to my custom binary format. see AbstractMessageConverterMethodProcessor#writeWithMessageConverters)
org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation
client sends
headers {Accept: [application/custom-binary, application/json]
server's controller is configured to
// pseudo code
#RequestMapping(method = GET, produces = {"application/custom-binary", APPLICATION_JSON_VALUE})
public BannerMetaCollection get(#RequestParam(value = "q") UUID[] q) {
if (q != null) {
return service.getAllDataWith(q);
} else {
throw new IllegalArgumentException("invalid data");
}
}
// pseudo code
public class RestExceptionResolverSupport extends ResponseEntityExceptionHandler {
#ExceptionHandler
public ResponseEntity<Object> illegalArgumentException(IllegalArgumentException ex, WebRequest request {
Object body = errorResponse()
.withCode(BAD_REQUEST)
.withDescription("Request sent is invalid")
.withMessage(ex.getMessage())
.build());
return new ResponseEntity<Object>(body, new HttpHeaders(), HttpStatus.BAD_REQUEST);
}
}
any hints?

Answer 1

What I do to get this to work is that a let my endpoint method return a ResponseEntity and I don't declare what content is produced in the #RequestMapping annotation. I then set the Content-type header myself before returning the response, e.g.
// pseudo code
#RequestMapping(method = GET)
public ResponseEntity<BannerMetaCollection> get(#RequestParam(value = "q") UUID[] q) {
if (q != null) {
HttpHeaders headers = new HttpHeaders();
headers.add(HttpHeaders.CONTENT_TYPE, "application/custom-binary");
return new ResponseEntity<>(service.getAllDataWith(q),
headers,
HttpStatus.OK);
} else {
throw new IllegalArgumentException("invalid data");
}
}