Spring MVC异常处理中抛出新异常的处理

项目中使用了全局异常处理，如下

@ControllerAdvice
public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {

    public static final String RESPONSE_ERROR = "Error";

    @Autowired
    MailPublisher mailPublisher;

    /**
     * Exception handler
     *
     * @param ex
     * @param request
     * @return
     */
    @ExceptionHandler(value = {Exception.class})
    public ResponseEntity handleExceptions(Exception ex, WebRequest request) {
        logger.error("Exception", ex);
        // Send email to administrator 如果这里出现异常呢？
        mailPublisher.publishMailToAdministrator(ex);
        return handleExceptionInternal(ex, RESPONSE_ERROR, new HttpHeaders(), HttpStatus.INTERNAL_SERVER_ERROR, request);
    }
}

但是如果异常处理中抛出了新的异常呢？这样就会导致返回的response不是我们定义的RESPONSE_ERROR字符串常量，而是默认的JSON格式：

{
    "timestamp": 1531362962859,
    "status": 500,
    "error": "Internal Server Error",
    "message": "test exception",
    "path": "/app/test"
}

或者如果我们还保持这种格式，但是想添加一些字段呢？

这两个问题是相关的，解决了问题2也就解决了问题1，那先看问题2。默认的error处理在BasicErrorController，默认异常URL是“/error”，这里有针对html和json的处理，如果需要其他响应格式的，比如plain/text，可以自己写个ErrorController。

/**
 * Basic global error {@link Controller}, rendering {@link ErrorAttributes}. More specific
 * errors can be handled either using Spring MVC abstractions (e.g.
 * {@code @ExceptionHandler}) or by adding servlet
 * {@link AbstractServletWebServerFactory#setErrorPages server error pages}.
 *
 * @author Dave Syer
 * @author Phillip Webb
 * @author Michael Stummvoll
 * @author Stephane Nicoll
 * @see ErrorAttributes
 * @see ErrorProperties
 */
@Controller
@RequestMapping("${server.error.path:${error.path:/error}}")
public class BasicErrorController extends AbstractErrorController {

    @RequestMapping(produces = "text/html")
    public ModelAndView errorHtml(HttpServletRequest request,
            HttpServletResponse response) {
        HttpStatus status = getStatus(request);
        Map model = Collections.unmodifiableMap(getErrorAttributes(
                request, isIncludeStackTrace(request, MediaType.TEXT_HTML)));
        response.setStatus(status.value());
        ModelAndView modelAndView = resolveErrorView(request, response, status, model);
        return (modelAndView != null ? modelAndView : new ModelAndView("error", model));
    }

    @RequestMapping
    @ResponseBody
    public ResponseEntity> error(HttpServletRequest request) {
        Map body = getErrorAttributes(request,
                isIncludeStackTrace(request, MediaType.ALL));
        HttpStatus status = getStatus(request);
        return new ResponseEntity<>(body, status);
    }

}

我们可以自己写个ErrorController来替换默认BasicErrorController来自定义响应内容:

@Controller
public class AppErrorController implements ErrorController {

    @Override
    public String getErrorPath() {
        return "/error";
    }

    @RequestMapping("/error")
    public ResponseEntity handleError(HttpServletRequest request) {
        Object status = request.getAttribute(RequestDispatcher.ERROR_STATUS_CODE);
        HttpStatus httpStatus;

        if (status != null) {
            Integer statusCode = Integer.valueOf(status.toString());
            httpStatus = HttpStatus.valueOf(statusCode);
        } else {
            httpStatus = HttpStatus.INTERNAL_SERVER_ERROR;
        }
        return new ResponseEntity<>(RESPONSE_ERROR, httpStatus);
    }
}

或者在配置类中自定义 ErrorAttributes ，添加自定义字段，默认返回的JSON中就会有自定义的字段。

    @Bean
    public ErrorAttributes errorAttributes() {
        return new DefaultErrorAttributes() {
            @Override
            public Map getErrorAttributes(
                    RequestAttributes requestAttributes,
                    boolean includeStackTrace) {
                Map errorAttributes = super.getErrorAttributes(requestAttributes, includeStackTrace);
                Object errorMessage = requestAttributes.getAttribute(RequestDispatcher.ERROR_MESSAGE, RequestAttributes.SCOPE_REQUEST);
                if (errorMessage != null) {
                    errorAttributes.put("message", errorMessage);
                }
                return errorAttributes;
            }
        };
    }

---

针对问题1，除了自定义ErrorController外，还可以在异常处理中添加try-catch来处理。

参考：

https://blog.jdriven.com/2016/06/spicy-spring-custom-error-json-response-with-errorattributes/

https://github.com/spring-projects/spring-boot/issues/1731