Description
I'm using Spring Webflux and seeing 406 errors when both of the following occur:
- Exceptions are returned from the the Reactive stream instead of the controller method itself.
- When the controller method produces a different ContentType then the ExceptionHandler.
This is reproducible using SpringBoot v2.0.3 and v2.1.0-BUILD-SNAPSHOT (as of today).
@RestController
@RequiredArgsConstructor
class BinaryTestController {
private final AccessKeyValidationService accessKeyValidationService;
@GetMapping(path = "/binary-test", produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
Mono<byte[]> test(@RequestParam("apiKey") String apiKey, @RequestParam(name = "failFirst", required = false) boolean failFirst) {
if (failFirst) { throw new IllegalArgumentException();}
return Mono.just(apiKey)
.filterWhen(accessKeyValidationService::isValid)
.switchIfEmpty(Mono.error(new IllegalAccessException()))
.then(Mono.just("test".getBytes(StandardCharsets.UTF_8)));
}
@ExceptionHandler(IllegalArgumentException.class)
ResponseEntity<Mono<BadResponse>> handleIllegalArgumentException() {
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
return new ResponseEntity<>(Mono.just(new BadResponse("better luck next time")), headers, HttpStatus.BAD_REQUEST);
}
@ExceptionHandler(IllegalAccessException.class)
ResponseEntity<Mono<BadResponse>> handleIllegalAccessException() {
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
return new ResponseEntity<>(Mono.just(new BadResponse("access denied")), headers, HttpStatus.FORBIDDEN);
}
@Data
class BadResponse {
private final String developerMessage;
}
}The AccessKeyValidationService does a blocking lookup, so naturally needs to return a Mono and thus needs to be part of the Mono returned from the controller:
@Service
class AccessKeyValidationService {
Mono<Boolean> isValid(String accessKey) {
return Mono.defer(() -> Mono.just(blockingLookup(accessKey)))
.subscribeOn(Schedulers.elastic());
}
private Boolean blockingLookup(String accessKey) {
//Some blocking lookup...
return accessKey.equals("good");
}
}
A valid apiKey, results in proper binary output:
$ http localhost:8080/binary-test apiKey==good
HTTP/1.1 200 OK
Content-Length: 4
Content-Type: application/octet-stream
test
When I throw an exception before the Reactive Stream, I get the intended JSON output:
$ http localhost:8080/binary-test apiKey==good failFirst==true
HTTP/1.1 400 Bad Request
Content-Length: 44
Content-Type: application/json;charset=UTF-8
{
"developerMessage": "better luck next time"
}
But when I trigger the steam to error with an IllegalAccessException, I get a 406:
$ http localhost:8080/binary-test apiKey==bad
HTTP/1.1 406 Not Acceptable
Content-Length: 157
Content-Type: application/json;charset=UTF-8
{
"error": "Not Acceptable",
"message": "Could not find acceptable representation",
"path": "/binary-test",
"status": 406,
"timestamp": "2018-06-30T05:23:09.820+0000"
}
If I put a breakpoint in the handleIllegalAccessException method, it stops as expected.
If I switch the return type for the controller method to JSON it works as expected.
Is there something else I need to do to switch the response type when erroring out the returned Mono? Or some other way to resolve it?
Here's a repo with a failing unit test reproducing the problem: https://github.com/pluttrell/spring-webflux-binary-response-exception-handling-example