SpringMVC源码情操陶冶-AbstractHandlerExceptionResolver-优快云博客

本文介绍了SpringMVC中异常处理的基本原理与配置方法，包括默认的异常解析器及自定义异常处理流程。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

springmvc支持服务端在处理业务逻辑过程中出现异常的时候可以配置相应的ModelAndView对象返回给客户端，本文介绍springmvc默认的几种HandlerExceptionResolver类

实际应用

springmvc的xml配置化-Exception配置

<bean id="exceptionHandler" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
    <!--设置默认返回viewName，通常与freemarker引擎搭配使用-->
    <property name="defaultErrorView" value="error/defaultError" />
    <!--设置默认返回response status-->
    <property name="defaultStatusCode" value="500" />
    
    <!--配置相应的异常类与viewName的映射-->
    <property name="exceptionMappings">
        <props>
            <prop key="SessionTimeoutException">redirect:../login.html</prop>
            <prop key="AuthenticationException">error/403</prop>
        </props>
    </property>
</bean>

以上的配置会对出SessionTimeoutException异常则跳转至login页面，对AuthenticationException异常则跳转至403页面，对其他的异常则默认跳转至defaultError页面呈现并返回500的错误码

HandlerExceptionResolver-异常解析接口

接口内只有一个方法resolveException()，通过解析异常查询配置以得到符合条件的ModelAndView对象

    /**
     * Try to resolve the given exception that got thrown during handler execution,
     * returning a {@link ModelAndView} that represents a specific error page if appropriate.
     * <p>The returned {@code ModelAndView} may be {@linkplain ModelAndView#isEmpty() empty}
     * to indicate that the exception has been resolved successfully but that no view
     * should be rendered, for instance by setting a status code.
     * @param request current HTTP request
     * @param response current HTTP response
     * @param handler the executed handler, or {@code null} if none chosen at the
     * time of the exception (for example, if multipart resolution failed)
     * @param ex the exception that got thrown during handler execution
     * @return a corresponding {@code ModelAndView} to forward to, or {@code null}
     * for default processing
     */
    ModelAndView resolveException(
            HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex);

AbstractHandlerExceptionResolver-异常解析抽象基类

所有的spring内置异常解析类都继承于此，直奔主题看resolveException()方法

    @Override
    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response,
            Object handler, Exception ex) {
        //判断是否需要解析
        if (shouldApplyTo(request, handler)) {
            //此处一般是判断内部属性preventResponseCaching是否为true，是则设置响应包头cache-control:no-store
            prepareResponse(ex, response);
            //使用模板方法doResolveException()方法供子类实现
            ModelAndView result = doResolveException(request, response, handler, ex);
            if (result != null) {
                //日志打印一发
                logException(ex, request);
            }
            return result;
        }
        else {
            return null;
        }
    }

附带着分析下shouldApplyTo()方法

    /**
    **可以配置mappedHandlers和mappedHandlerClasses属性来特定匹配
    **默认情况下两者都为空则直接返回true，表明对所有的handler都进行异常解析
    */
    protected boolean shouldApplyTo(HttpServletRequest request, Object handler) {
        //此处的handler一般为bean对象
        if (handler != null) {
            if (this.mappedHandlers != null && this.mappedHandlers.contains(handler)) {
                return true;
            }
            if (this.mappedHandlerClasses != null) {
                for (Class<?> handlerClass : this.mappedHandlerClasses) {
                    if (handlerClass.isInstance(handler)) {
                        return true;
                    }
                }
            }
        }
        // Else only apply if there are no explicit handler mappings.
        return (this.mappedHandlers == null && this.mappedHandlerClasses == null);
    }

1. SimpleMappingExceptionResolver-异常映射实现类

比较简单的实现类，可以配绑定viewName和exception以完成简单的异常映射视图页面

    protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response,
            Object handler, Exception ex) {

        // Expose ModelAndView for chosen error view.
        String viewName = determineViewName(ex, request);
        if (viewName != null) {
            //如果配置了statusCodes属性，则对此异常的状态码进行设置
            Integer statusCode = determineStatusCode(request, viewName);
            if (statusCode != null) {
                applyStatusCodeIfPossible(request, response, statusCode);
            }
            //创建ModelAndView对象
            return getModelAndView(viewName, ex, request);
        }
        else {
            return null;
        }
    }

针对以上的源码我们分两步去简单分析下

SimpleMappingExceptionResolver#determineViewName()-找寻viewName

    protected String determineViewName(Exception ex, HttpServletRequest request) {
        String viewName = null;
        //判断异常是否属于excludeExceptions集合内，是则直接返回null
        if (this.excludedExceptions != null) {
            for (Class<?> excludedEx : this.excludedExceptions) {
                if (excludedEx.equals(ex.getClass())) {
                    return null;
                }
            }
        }
        // Check for specific exception mappings.
        // 从exceptionMappings集合内根据exception获取到相应的viewName
        if (this.exceptionMappings != null) {
            viewName = findMatchingViewName(this.exceptionMappings, ex);
        }
        //当exceptionMappings集合内不存在指定的exception但是默认视图指定则直接返回默认视图
        if (viewName == null && this.defaultErrorView != null) {
            viewName = this.defaultErrorView;
        }
        return viewName;
    }

excludedExceptions集合可以过滤指定的exception，对其不进行解析直接返回null。可配置
exceptionMappings绑定了exception与viewName的关系，如果在其集合内没找到相应的viewName，但是defaultErrorView属性指定，则会直接返回defaultErrorView对应的视图

SimpleMappingExceptionResolver#getModelAndView()-创建ModelAndView对象

    protected ModelAndView getModelAndView(String viewName, Exception ex) {
        ModelAndView mv = new ModelAndView(viewName);
        //exceptionAttribute默认为exception
        if (this.exceptionAttribute != null) {
            //将exception信息添加到model中
            mv.addObject(this.exceptionAttribute, ex);
        }
        return mv;
    }

主要就是将exceptionAttribute对应的参数值默认为exception属性添加到视图对象的model中

2. ResponseStatusExceptionResolver-响应状态异常解析类

主要是解析带有@ResponseStatus的异常类，将其中的异常信息描述直接返回给客户端

    @Override
    protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response,
            Object handler, Exception ex) {
        //获取相应类上的注解@ResponseStatus
        ResponseStatus responseStatus = AnnotatedElementUtils.findMergedAnnotation(ex.getClass(), ResponseStatus.class);
        if (responseStatus != null) {
            try {
                return resolveResponseStatus(responseStatus, request, response, handler, ex);
            }
            catch (Exception resolveEx) {
                logger.warn("Handling of @ResponseStatus resulted in Exception", resolveEx);
            }
        }
        else if (ex.getCause() instanceof Exception) {
            ex = (Exception) ex.getCause();
            //递归
            return doResolveException(request, response, handler, ex);
        }
        return null;
    }

ResponseStatusExceptionResolver#resolveResponseStatus()-返回异常信息给客户端

读取@ResponseStatus注解信息，返回异常内容给客户端

    protected ModelAndView resolveResponseStatus(ResponseStatus responseStatus, HttpServletRequest request,
            HttpServletResponse response, Object handler, Exception ex) throws Exception {
        //状态码
        int statusCode = responseStatus.code().value();
        //异常原因描述
        String reason = responseStatus.reason();
        if (this.messageSource != null) {
            reason = this.messageSource.getMessage(reason, null, reason, LocaleContextHolder.getLocale());
        }
        //通过response对象直接返回错误信息给客户端
        if (!StringUtils.hasLength(reason)) {
            response.sendError(statusCode);
        }
        else {
            //通过response对象直接返回错误信息给客户端
            response.sendError(statusCode, reason);
        }
        return new ModelAndView();
    }

3. DefaultHandlerExceptionResolver-springmvc默认的异常解析处理

源码就不公布了，读者可自行去查询，基本都是调用response的sendError()方法返回错误信息给客户端。本文对其中的异常归下类

请求方式异常
HttpRequestMethodNotSupportedException-服务端不支持相应的请求方法
HttpMediaTypeNotSupportedException/HttpMediaTypeNotAcceptableException-服务端/客户端不支持相应的mediaType，比如application/json
MissingPathVariableException-@PathVaribale指定参数请求中不包含
MissingServletRequestParameterException/ServletRequestBindingException-请求参数绑定错误
MethodArgumentNotValidException-@Valid注解指定的参数校验失败
AsyncRequestTimeoutException-异步请求超时
消息内容异常
ConversionNotSupportedException-服务端找寻不到相应的Convert对象来解析javabean
TypeMismatchException-设置javabean属性类型出错
HttpMessageNotReadableException/HttpMessageNotWritableException-消息内容不可读/不可写
MissingServletRequestPartException-文件上传类错误，可能请求没有multipart/form-data或者服务不支持文件上传
NoHandlerFoundException-handler处理器没有找到，即可能没有对应的请求处理供响应

4. ExceptionHandlerExceptionResolver-处理handlerMethod对象过程中的异常

具体的逻辑本文则不展开了，简述下其中的逻辑：
当处理handlerMethod业务逻辑过程中出现了异常，则此解析器

尝试从handlerMethod所在的class类去找寻是否含有@ExceptionHandler注解的方法
判断@ExceptionHandler指定的exception类与产生的异常一致，一致则执行相应的方法，当有多个@ExceptionHandler(value)，则默认采用第一个
当上述在class类找寻不到则尝试判断class类是否含有@ControllerAdvice注解，有则按照上述第一二步的步骤再次找寻@ControllerAdvice指定的类