can some one explain me what is the usage of extending ResponseEntityExceptionHandler. If Ido not extend also ResponseEntityExceptionHandler GlobalExceptionHandler is working and sending the response to client.

@ControllerAdvice
public class GlobalExceptionHandler  extends ResponseEntityExceptionHandler{
    @ExceptionHandler({ UserNotFoundException.class, ContentNotAllowedException.class })
    public final ResponseEntity<ApiError> handleException(Exception ex, WebRequest request) {
        HttpHeaders headers = new HttpHeaders();

        if (ex instanceof UserNotFoundException) {
            HttpStatus status = HttpStatus.NOT_FOUND;
            UserNotFoundException unfe = (UserNotFoundException) ex;

            return handleUserNotFoundException(unfe, headers, status, request);
        } else if (ex instanceof ContentNotAllowedException) {
            HttpStatus status = HttpStatus.BAD_REQUEST;
            ContentNotAllowedException cnae = (ContentNotAllowedException) ex;

            return handleContentNotAllowedException(cnae, headers, status, request);
        } else {
            HttpStatus status = HttpStatus.INTERNAL_SERVER_ERROR;
            return handleExceptionInternal(ex, null, headers, status, request);
        }
    }

}

@ControllerAdvice
public class GlobalExceptionHandler{
    @ExceptionHandler({ UserNotFoundException.class, ContentNotAllowedException.class })
    public final ResponseEntity<ApiError> handleException(Exception ex, WebRequest request) {
        HttpHeaders headers = new HttpHeaders();

        if (ex instanceof UserNotFoundException) {
            HttpStatus status = HttpStatus.NOT_FOUND;
            UserNotFoundException unfe = (UserNotFoundException) ex;

            return handleUserNotFoundException(unfe, headers, status, request);
        } else if (ex instanceof ContentNotAllowedException) {
            HttpStatus status = HttpStatus.BAD_REQUEST;
            ContentNotAllowedException cnae = (ContentNotAllowedException) ex;

            return handleContentNotAllowedException(cnae, headers, status, request);
        } else {
            HttpStatus status = HttpStatus.INTERNAL_SERVER_ERROR;
            return handleExceptionInternal(ex, null, headers, status, request);
        }
    }

}

CodePudding user response：

ResponseEntityExceptionHandler is used when one is generally satisfied with Spring's default ExceptionHandlers - except for a few, which may then be overridden.

Have a look at all the protected methods in the API documentation: ResponseEntityExceptionHandler

Your GlobalExceptionHandler is already accepting any Exceptions and custom handling two specific Exceptions.

If you insist on using ResponseEntityExceptionHandler, a similar effect may be achieved by extending the class and implementing handleExceptionInternal():

@ControllerAdvice
public class CustomRestExceptionHandler extends ResponseEntityExceptionHandler {
    @Override
    public handleExceptionInternal() {
        ...
    }
}