标签：return completed bind eal pos 理解 let 属性 roc
Spring MVC 通过 HandlerExceptionResolver 处理程序的异常，包括 Handler 映射、数据绑定以及目标方法执行时发生的异常。
SpringMVC 提供的 HandlerExceptionResolver 的实现类
DispatcherServlet 默认装配的 HandlerExceptionResolver ：
① 使用了 <mvc:annotation-driven/> 配置：
1)主要处理 Handler 中用 @ExceptionHandler 注解定义的方法
2)@ExceptionHandler 注解定义的方法优先级问题：例如发生的是NullPointerException，但是声明的异常有 RuntimeException 和 Exception，此候会根据异常的最近继承关系找到继承深度最浅的那个 @ExceptionHandler 注解方法，即标记了 RuntimeException 的方法
3)ExceptionHandlerMethodResolver 内部若找不到@ExceptionHandler 注解的话，会找 @ControllerAdvice 中的@ExceptionHandler 注解方法
对一些特殊的异常进行处理，比如：
NoSuchRequestHandlingMethodException、
HttpRequestMethodNotSupportedException、
HttpMediaTypeNotSupportedException、
HttpMediaTypeNotAcceptableException等。
如果希望对所有异常进行统一处理，可以使用 SimpleMappingExceptionResolver，它将异常类名映射为视图名，即发生异常时使用对应的视图报告异常
<!--简单异常映射解析器，对于用户 名存在throw的异常进行映射跳转到指定视图 --> <bean id="SimpleMappingExceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver"> <property name="exceptionMappings"> <!-- key属性是异常类型 --> <!-- 标签体配置目标视图 --> <props> <prop key="com.lamsey.survey.e.UserNameAlreadyExistException">guest/user_regist</prop> </props> </property> </bean>
源码分析：
首先springmvc核心流程如下：
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception { boolean errorView = false; if (exception != null) { if (exception instanceof ModelAndViewDefiningException) { logger.debug("ModelAndViewDefiningException encountered", exception); mv = ((ModelAndViewDefiningException) exception).getModelAndView(); } else { Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null); //处理异常 mv = processHandlerException(request, response, handler, exception); errorView = (mv != null); } } // Did the handler return a view to render? if (mv != null && !mv.wasCleared()) { //这是正常的页面渲染流程 render(mv, request, response); if (errorView) { WebUtils.clearErrorRequestAttributes(request); } } else { if (logger.isDebugEnabled()) { logger.debug("Null ModelAndView returned to DispatcherServlet with name ‘" + getServletName() + "‘: assuming HandlerAdapter completed request handling"); } } if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) { // Concurrent handling started during a forward return; } if (mappedHandler != null) { mappedHandler.triggerAfterCompletion(request, response, null); } }
1）判断有无异常
//处理异常 mv = processHandlerException(request, response, handler, exception);
2）对视图进行渲染
//这是正常的页面渲染流程 render(mv, request, response);
遍历获取异常处理解析器
protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { // Check registered HandlerExceptionResolvers... ModelAndView exMv = null; for (HandlerExceptionResolver handlerExceptionResolver : this.handlerExceptionResolvers) { exMv = handlerExceptionResolver.resolveException(request, response, handler, ex); if (exMv != null) { break; } } if (exMv != null) { if (exMv.isEmpty()) { return null; } // We might still need view name translation for a plain error model... if (!exMv.hasView()) { exMv.setViewName(getDefaultViewName(request)); } if (logger.isDebugEnabled()) { logger.debug("Handler execution resulted in exception - forwarding to resolved error view: " + exMv, ex); } WebUtils.exposeErrorRequestAttributes(request, ex, getServletName()); return exMv; } throw ex; }
try { if (ex instanceof NoSuchRequestHandlingMethodException) { return handleNoSuchRequestHandlingMethod((NoSuchRequestHandlingMethodException) ex, request, response, handler); } else if (ex instanceof HttpRequestMethodNotSupportedException) { return handleHttpRequestMethodNotSupported((HttpRequestMethodNotSupportedException) ex, request, response, handler); } else if (ex instanceof HttpMediaTypeNotSupportedException) { return handleHttpMediaTypeNotSupported((HttpMediaTypeNotSupportedException) ex, request, response, handler); } else if (ex instanceof HttpMediaTypeNotAcceptableException) { return handleHttpMediaTypeNotAcceptable((HttpMediaTypeNotAcceptableException) ex, request, response, handler); } else if (ex instanceof MissingServletRequestParameterException) { return handleMissingServletRequestParameter((MissingServletRequestParameterException) ex, request, response, handler); } else if (ex instanceof ServletRequestBindingException) { return handleServletRequestBindingException((ServletRequestBindingException) ex, request, response, handler); } else if (ex instanceof ConversionNotSupportedException) { return handleConversionNotSupported((ConversionNotSupportedException) ex, request, response, handler); } else if (ex instanceof TypeMismatchException) { return handleTypeMismatch((TypeMismatchException) ex, request, response, handler); } else if (ex instanceof HttpMessageNotReadableException) { return handleHttpMessageNotReadable((HttpMessageNotReadableException) ex, request, response, handler); } else if (ex instanceof HttpMessageNotWritableException) { return handleHttpMessageNotWritable((HttpMessageNotWritableException) ex, request, response, handler); } else if (ex instanceof MethodArgumentNotValidException) { return handleMethodArgumentNotValidException((MethodArgumentNotValidException) ex, request, response, handler); } else if (ex instanceof MissingServletRequestPartException) { return handleMissingServletRequestPartException((MissingServletRequestPartException) ex, request, response, handler); } else if (ex instanceof BindException) { return handleBindException((BindException) ex, request, response, handler); } else if (ex instanceof NoHandlerFoundException) { return handleNoHandlerFoundException((NoHandlerFoundException) ex, request, response, handler); } } catch (Exception handlerException) { logger.warn("Handling of [" + ex.getClass().getName() + "] resulted in Exception", handlerException); } return null; }
标签：return completed bind eal pos 理解 let 属性 roc
原文地址：http://www.cnblogs.com/limingxian537423/p/7391550.html
