@ControllerAdvice and @ExceptionHandler not getting triggered for my RestController

In order to have unified exception handling throughout the application I am using Error Handling for REST with Spring solution#3 which uses @ControllerAdvice along with @ExceptionHandler.

Spring version: 4.3.22.RELEASE

Spring Boot version: 1.5.19.RELEASE

This is a Spring boot application and following is my package structure.

src/main/java
  com.test.app.controller
     MyRestController.java       -- This is my Rest controller
  com.test.app.handler
     RestExceptionHandler.java   -- This is my ControllerAdvice class

Following is my ControllerAdvice code and one of the Controller throws InvalidDataException but still the corresponding @ExceptionHandler is not called. Instead I am getting Unexpected 'e' as the response body with http 400.

@ControllerAdvice
public class RestExceptionHandler {

    @ExceptionHandler(InvalidDataException.class)
    @ResponseStatus(value = HttpStatus.BAD_REQUEST)
    public @ResponseBody ErrorResponse handleValidationError(final InvalidDataException ex,
                                                             final WebRequest request) {
        log.error("InvalidDataException message:{} ", ex.getMessage());
        return getExceptionResponse("Failed with Invalid data" + ex.getMessage(), HttpStatus.BAD_REQUEST.value());
    }


    private ErrorResponse getExceptionResponse(final String message, final Integer errorCode) {
        final ErrorResponse exceptionResponse = new ErrorResponse();
        exceptionResponse.setErrorCode(errorCode.toString());
        exceptionResponse.setErrorDescription(message);
        log.error("message:{}", exceptionResponse);
        return exceptionResponse;
    }
}

I looked at other post on SO as well as other forums where they mentioned to use @EnableWebMvc and @ComponentScan etc. but nothing helped. Could someone please help me understand what am I missing?

Following is my Controller and corresponding interface.

@RestController
public class MyRestController implements MyApi {

    @Override
    public ResponseEntity<List<MyResponse>> myGet(@RequestHeader(value = "a") String a,
                                                               @RequestHeader(value = "b") String b,
                                                               @RequestHeader(value = "c") String c,
                                                               @RequestHeader(value = "d") String d,
                                                               @RequestHeader(value = "e") String e,
                                                               @RequestHeader(value = "f") String f,
                                                               @RequestHeader(value = "g") String g) {

      List<MyResponse> responses = service.getData(c, d, e, f); // This throws exception
      return new ResponseEntity<>(responses, HttpStatus.OK);
    }
}


@Validated
@Api(value = "My", description = "the My API")
//This is generated interface through swagger codegen
public interface MyApi {

    @ApiOperation(value = "", nickname = "myGet", notes = "", response = MyResponse.class, responseContainer = "List")
    @ApiResponses(value = {
        @ApiResponse(code = 200, message = "normal response", response = MyResponse.class, responseContainer = "List"),
        @ApiResponse(code = 400, message = "Request is invalid", response = ErrorResponse.class),
        @ApiResponse(code = 401, message = "", response = ErrorResponse.class),
        @ApiResponse(code = 404, message = "", response = ErrorResponse.class),
        @ApiResponse(code = 405, message = "", response = ErrorResponse.class),
        @ApiResponse(code = 409, message = "", response = ErrorResponse.class),
        @ApiResponse(code = 500, message = "Internal Server Error", response = ErrorResponse.class),
        @ApiResponse(code = 503, message = "Service Unavailable", response = ErrorResponse.class) })
    @RequestMapping(value = "/v1/test",
        produces = { "application/json" }, 
        method = RequestMethod.GET)
    default ResponseEntity<List<MyResponse>> myGet(@ApiParam(value = "a" ,required=true) @RequestHeader(value="a", required=true) String a,
                                                   @ApiParam(value = "b" ,required=true) @RequestHeader(value="b", required=true) String b,
                                                   @ApiParam(value = "c" ,required=true) @RequestHeader(value="c", required=true) String c,
                                                   @ApiParam(value = "d" ,required=true) @RequestHeader(value="d", required=true) String d,
                                                   @ApiParam(value = "e" ,required=true) @RequestHeader(value="e", required=true) String e,
                                                   @ApiParam(value = "f" ,required=true) @RequestHeader(value="f", required=true) String f,
                                                   @ApiParam(value = "g" ,required=true) @RequestHeader(value="g", required=true) String g) {
        getRequest().ifPresent(request -> {
            for (MediaType mediaType: MediaType.parseMediaTypes(request.getHeader("Accept"))) {
                if (mediaType.isCompatibleWith(MediaType.valueOf("application/json"))) {
                    ApiUtil.setExampleResponse(request, "application/json", "{  \"aNum\" : 0,  \"cNum\" : \"cNum\"}");
                    break;
                }
            }
        });
        return new ResponseEntity<>(HttpStatus.NOT_IMPLEMENTED);
    }
}

Following is the code snippet from my GlobalExceptionHandler

class GlobalExceptionHandler extends ExceptionHandlerExceptionResolver implements HandlerExceptionResolver, Ordered, InitializingBean {
    ...
    @Override
    protected ServletInvocableHandlerMethod getExceptionHandlerMethod(HandlerMethod handlerMethod, Exception exception) {
        if (exception instanceof com.myframework.SystemException) {
            return new ServletInvocableHandlerMethod(this, exceptionMethods.get(com.myframework.SystemException.class.getName()));
        } else if (exception instanceof GenericApplicationException) {
            return new ServletInvocableHandlerMethod(this, exceptionMethods.get(com.myframework.GenericApplicationException.class.getName()));
        } else {
            return null;
        }
    }
    ....
}

It should work. Some possible causes that make it fails may be :

1. The RestExceptionHandler is not declared as a spring bean yet ? @SpringBootApplication by default will only scan the spring beans to register under its package and all of its sub-packages.

2. The controller is actually not throwing InvalidDataException but other exception ?

Anyway I suggest you to make the following changes to check if RestExceptionHandler is get called .

In your spring boot main application class , explicitly register RestExceptionHandler as a spring bean using @Import

@SpringBootApplication
@Import(RestExceptionHandler.class)
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Also in the RestExceptionHandler , also include a method to catch the most generic Exception :

@ControllerAdvice
public class RestExceptionHandler {

    @ExceptionHandler(Exception.class)
    @ResponseStatus(value = HttpStatus.BAD_REQUEST)
    public ErrorResponse handleGenericException(final Exception ex ,final WebRequest request) {
        System.out.println("handleGenericException ....");
        return getExceptionResponse("Failed with Invalid data" + ex.getMessage(), HttpStatus.BAD_REQUEST.value());
    }
}

Please let me know if the RestExceptionHandler will get called after making these changes.