Spring controller advice does not correctly handle a CompletableFuture completed exceptionally

Question

I am using Spring Boot 1.5, and I have a controller that executes asynchronously, returning a CompletableFuture<User>.

@RestController
@RequestMapping("/users")
public class UserController {

    @Autowired
    private final UserService service;

    @GetMapping("/{id}/address")
    public CompletableFuture<Address> getAddress(@PathVariable String id) {
        return service.findById(id).thenApply(User::getAddress);
    }
}

The method UserService.findById can throw a UserNotFoundException. So, I develop dedicated controller advice.

@ControllerAdvice(assignableTypes = UserController .class)
public class UserExceptionAdvice {
    @ExceptionHandler(UserNotFoundException.class)
    @ResponseStatus(HttpStatus.NOT_FOUND)
    @ResponseBody
    public String handleUserNotFoundException(UserNotFoundException ex) {
        return ex.getMessage();
    }
}

The problem is that tests are not passing returning an HTTP 500 status and not a 404 status in case of an unknown user request to the controller.

What's going on?

Answer 1

For those of you who still run into trouble with this : even though Spring correctly unwraps the ExecutionException, it doesn't work if you have a handler for the type "Exception", which gets chosen to handle ExecutionException, and not the handler for the underlying cause.

The solution : create a second ControllerAdvice with the "Exception" handler, and put @Order(Ordered.HIGHEST_PRECEDENCE) on your regular handler. That way, your regular handler will go first, and your second ControllerAdvice will act as a catch all.