Return JSON on uncaught exceptions in Spring controllers

Question

I have a Spring controller annotated with @RestController and it is returning JSON. I also have a class annotated with @ControllerAdvice with @ExceptionHandlers related to some custom exceptions. I am using Tomcat to serve this RESTful API. I'd like to have any non-custom exception such as one coming from a 3rd party library or a NullPointerException be caught and returned with status 500 - Internal Server Error as JSON with a message instead of an HTML page showing the error.

If I use an @ExceptionHandler(Exception.class) in the controller advice it takes over all of Spring exceptions like MissingPathVariableException.class, which is not ideal. I've tried extending Spring's ResponseEntityExceptionHandler but this class is not annotated with @ResponseBody so does not return JSON.

1. How do you return JSON for uncaught and unknown exceptions (ones you can't plan for) in a Spring RESTful API without influencing Spring's internals?
2. How can I turn off returning HTML entirely and ensure only JSON responses no matter whether the request has an exception or not?

Answer 1

For returning JSON on uncaught exceptions you can use this code:

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestController;

@ControllerAdvice  
@RestController
public class GlobalExceptionHandler {

    private class JsonResponse {
        String message;

        public JsonResponse() {
        }

        public JsonResponse(String message) {
            super();
            this.message = message;
        }

        public String getMessage() {
            return message;
        }

        public void setMessage(String message) {
            this.message = message;
        }       
    }

    @ExceptionHandler(value = Exception.class)  
    public ResponseEntity<JsonResponse> handleException(Exception e) {
        return new ResponseEntity<JsonResponse>(new JsonResponse(e.getMessage()), HttpStatus.BAD_REQUEST);
    }

}

JSON result if exception is throwing:

{
    "message": "Something wrong!"
}

You can use this link for more detailed information about Spring exception handling (with code examples).