【SpringBoot】四、SpringBoot中全局异常统一处理

在服务器端出现异常，或者客户端请求出错时，直接返回异常信息对用户来说是非常不友好的，我们需要对异常信息进行统一处理

1、使用 @ControllerAdvice 注解的控制层的全局统一异常处理

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(Exception.class)
    public ModelAndView customException(Exception e) {
        ModelAndView mav = new ModelAndView();
        // 跳转到错误页面
        mav.setViewName("error");
        return mav;
    }
}

@ControllerAdvice 表示这是一个控制器增强类，当控制器发生异常且符合类中定义的拦截异常类，将会被拦截

@ExceptionHandler 则是定义拦截的异常类，可以是自定义异常类，例如：

@ExceptionHandler(value = MyException.class)
@ResponseBody
public JSONObject myErrorHandler(MyException exception) {
    JSONObject res = new JSONObject();
    res.put("code", exception.getCode());
    res.put("msg", exception.getMsg());
    return res;
}

当然，我们可以不返回页面，只返回异常信息

使用 @ControllerAdvice 只能捕获 Controller 层的异常，前提是 Controller 层没有对异常做 catch 处理

2、实现 ErrorController 接口

以下是网上一位博主给出的示例代码，博客地址为：https://blog.csdn.net/king_is_everyone/article/details/53080851

@Controller
@RequestMapping(value = "error")
@EnableConfigurationProperties({ServerProperties.class})
public class ExceptionController implements ErrorController {

    private ErrorAttributes errorAttributes;

    @Autowired
    private ServerProperties serverProperties;


    /**
     * 初始化ExceptionController
     *
     * @param errorAttributes
     */
    @Autowired
    public ExceptionController(ErrorAttributes errorAttributes) {
        Assert.notNull(errorAttributes, "ErrorAttributes must not be null");
        this.errorAttributes = errorAttributes;
    }


    /**
     * 定义404的ModelAndView
     *
     * @param request
     * @param response
     * @return
     */
    @RequestMapping(produces = "text/html", value = "404")
    public ModelAndView errorHtml404(HttpServletRequest request, HttpServletResponse response) {
        response.setStatus(getStatus(request).value());
        Map<String, Object> model = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.TEXT_HTML));
        return new ModelAndView("error/404", model);
    }

    /**
     * 定义404的JSON数据
     *
     * @param request
     * @return
     */
    @RequestMapping(value = "404")
    @ResponseBody
    public ResponseEntity<Map<String, Object>> error404(HttpServletRequest request) {
        Map<String, Object> body = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.TEXT_HTML));
        HttpStatus status = getStatus(request);
        return new ResponseEntity<Map<String, Object>>(body, status);
    }

    /**
     * 定义500的ModelAndView
     *
     * @param request
     * @param response
     * @return
     */
    @RequestMapping(produces = "text/html", value = "500")
    public ModelAndView errorHtml500(HttpServletRequest request, HttpServletResponse response) {
        response.setStatus(getStatus(request).value());
        Map<String, Object> model = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.TEXT_HTML));
        return new ModelAndView("error/500", model);
    }


    /**
     * 定义500的错误JSON信息
     *
     * @param request
     * @return
     */
    @RequestMapping(value = "500")
    @ResponseBody
    public ResponseEntity<Map<String, Object>> error500(HttpServletRequest request) {
        Map<String, Object> body = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.TEXT_HTML));
        HttpStatus status = getStatus(request);
        return new ResponseEntity<Map<String, Object>>(body, status);
    }


    /**
     * 确定是否应包含stacktrace属性
     *
     * @param request  the source request
     * @param produces the media type produced (or {@code MediaType.ALL})
     * @return if the stacktrace attribute should be included
     */
    protected boolean isIncludeStackTrace(HttpServletRequest request, MediaType produces) {
        ErrorProperties.IncludeStacktrace include = this.serverProperties.getError().getIncludeStacktrace();
        if (include == ErrorProperties.IncludeStacktrace.ALWAYS) {
            return true;
        }
        if (include == ErrorProperties.IncludeStacktrace.ON_TRACE_PARAM) {
            return getTraceParameter(request);
        }
        return false;
    }


    /**
     * 获取错误的信息
     *
     * @param request
     * @param includeStackTrace
     * @return
     */
    private Map<String, Object> getErrorAttributes(HttpServletRequest request, boolean includeStackTrace) {
        RequestAttributes requestAttributes = new ServletRequestAttributes(request);
        return this.errorAttributes.getErrorAttributes((WebRequest) requestAttributes, includeStackTrace);
    }

    /**
     * 是否包含trace
     *
     * @param request
     * @return
     */
    private boolean getTraceParameter(HttpServletRequest request) {
        String parameter = request.getParameter("trace");
        if (parameter == null) {
            return false;
        }
        return !"false".equals(parameter.toLowerCase());
    }

    /**
     * 获取错误编码
     *
     * @param request
     * @return
     */
    private HttpStatus getStatus(HttpServletRequest request) {
        Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
        if (statusCode == null) {
            return HttpStatus.INTERNAL_SERVER_ERROR;
        }
        try {
            return HttpStatus.valueOf(statusCode);
        } catch (Exception ex) {
            return HttpStatus.INTERNAL_SERVER_ERROR;
        }
    }

    /**
     * 实现错误路径
     *
     * @return
     */
    @Override
    public String getErrorPath() {
        return "";
    }

}

总结：

1、@ControllerAdvice 定义多个拦截方法，拦截不同的异常类，并且可以获取抛出的异常信息
2、@ControllerAdvice 只能捕获进入 Controller 层的异常，比如404,401等错误无法捕获
3、ErrorController，该方式几乎可以处理所有的异常，包括未进入控制器的错误，比如404,401等错误

当然，前提是没有对异常做 catch 处理才能捕获到

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