No @ResponseBody returned from @ExceptionHandler in Spring boot app deployed in Tomcat

Question

I have a Spring Boot web app that runs just fine from STS but shows different behavior when running in Tomcat from a WAR file.

I use Thymeleaf to handle all my web pages but I have a couple pages that are using jQuery to send async calls and make user experience more dynamic.

Anyway, I have a Controller method that calls a service method which may throw a RuntimeException which I handle this way :

@ExceptionHandler(MyRuntimeException.class)
@ResponseStatus(HttpStatus.BAD_REQUEST)
public @ResponseBody String handleMyRuntimeException(MyRuntimeException exception) {
    return "Oops an error happened : " + exception.getMessage();
}

In JS, I use the response body I return above to display a message on screen.

That works perfectly fine when running my app in STS but once I switch to deploy it in Tomcat the ErrorPageFilter gets invoked and in doFilter() it does:

if (status >= 400) {
    handleErrorStatus(request, response, status, wrapped.getMessage());
    response.flushBuffer();
}

In handleErrorStatus() it creates an error with the status and associated message but doesn't return my response.

I haven't figured out how to solve this and I'd really appreciate if anybody could help.

Thanks!

Fusain

For now, my workaround is to catch the Exception thrown by my service and return a JSON object with a SUCCESS or FAILURE status and corresponding message and / or result data. – Fusain

Answer 1

I went around this issue (I would think that is a Spring Boot issue) by doing the following.

1. Separate Rest and Mvc controllers See my question here : Spring MVC: Get i18n message for reason in @RequestStatus on a @ExceptionHandler

2. Inject Jackson converter and write response myself :

   @ControllerAdvice(annotations = RestController.class)
   @Priority(1)
   @ResponseBody
   public class RestControllerAdvice {
       @Autowired
       private MappingJackson2HttpMessageConverter jacksonMessageConverter;
   
       @ExceptionHandler(RuntimeException.class)
       @ResponseStatus(value = HttpStatus.BAD_REQUEST)
       public void handleRuntimeException(HttpServletRequest request, HttpServletResponse response, RuntimeException exception) {
           try {
               jacksonMessageConverter.write(new MyRestResult(translateMessage(exception)), MediaType.APPLICATION_JSON, new ServletServerHttpResponse(response));
               response.flushBuffer(); // Flush to commit the response
               } catch (IOException e) {
               e.printStackTrace();
           }
       }
   }
   

Fusain

It is important to call the flushBuffer() method or this won't work. – Fusain

What has really made a difference is that you've removed @ResponseStatus (see jira.spring.io/browse/SPR-8251). Instead you can simply return a ResponseEntity. There is no need to write yourself through Jackson. – Bradway

I'll try that thanks ! But if if I return HttpStatus.BAD_REQUEST in my ResponseEntity, wouldn't I get the same behavior ? – Fusain

Returning a new ResponseEntity<MyRestResult>(myRestResult, HttpStatus.BAD_REQUEST) produces the same result. I'll log a Boot issue. Thanks for your time. – Fusain

@DamienPolegato Thanks so much for your code. My @RestControllerAdvice annotated global exception-handler would correctly pass a ResponseEntity to the client as JSON, but it wouldn't pass it to client on a handler for @ExceptionHandler(value = ConstraintViolationException.class). You're solution let's me give a personlized Repsonse for constraints back to the client. – Famine

Couldn't get it to work with a ResponseEntity, but simply writing the response directly to HttpServletResponse made it work. So thanks for that. – Aulea