电脑如何做穿透外网网站,企业公司网页设计,绍兴seo网站管理,学院网站怎么做的问题#xff1a;异常处理器在SpringMVC中是如何进行初始化以及使用的#xff1f; Spring MVC提供处理异常的方式主要分为两种#xff1a; 1、实现HandlerExceptionResolver方式#xff08;HandlerExceptionResolver是一个接口#xff0c;在SpringMVC有一些默认的实现也可以…问题异常处理器在SpringMVC中是如何进行初始化以及使用的 Spring MVC提供处理异常的方式主要分为两种 1、实现HandlerExceptionResolver方式HandlerExceptionResolver是一个接口在SpringMVC有一些默认的实现也可以自定义异常处理器 2、ExceptionHandler注解方式。注解方式也有两种用法 1使用在Controller内部 2配置ControllerAdvice一起使用实现全局处理 下面的HandlerExceptionResolver接口的类的继承关系。 补充说明注解EnableWebMvc和mvc:annotation-driven / 这个注解得作用就是相当于再配置文件中加上mvc:annotation-driven / 本质都是会默认得注入一些SpringMVC得核心组件比如RequestMappingHandlerMapping与RequestMappingHandlerAdapter等而EnableWebMvc注解 也是一样得作用默认得会加载一些组件。EnableWebMvc通常是加载配置类上使用的在初始化父容器的时候会进行注解的解析然后装载默认组件。 不过SpringMVC中如果配置了 mvc:annotation-driven/ 或者使用了EnableWebMvc就会引入的 HandlerExceptionResolverComposite这个是包含ExceptionHandlerExceptionResolver、DefaultHandlerExceptionResolver、ResponseStatusExceptionResolver3个处理器的是一个组合模式下面会涉及到这个 一、启动源码分析
0、DispatcherServlet#initStrategies() 回归到DispatcherServlet在执行初始化策略中跳过其他看initHandlerExceptionResolvers(context) protected void initStrategies(ApplicationContext context) {initMultipartResolver(context);initLocaleResolver(context);initThemeResolver(context);initHandlerMappings(context);initHandlerAdapters(context);initHandlerExceptionResolvers(context);initRequestToViewNameTranslator(context);initViewResolvers(context);initFlashMapManager(context);}1 initHandlerExceptionResolvers() 找到类是HandlerExceptionResolver的Bean加入到handlerExceptionResolvers如果没有的话就用默认的。这里的默认是会取读取DispatcherServlet.properties private void initHandlerExceptionResolvers(ApplicationContext context) {this.handlerExceptionResolvers null;if (this.detectAllHandlerExceptionResolvers) {// Find all HandlerExceptionResolvers in the ApplicationContext, including ancestor contexts.MapString, HandlerExceptionResolver matchingBeans BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerExceptionResolver.class, true, false);if (!matchingBeans.isEmpty()) {this.handlerExceptionResolvers new ArrayList(matchingBeans.values());// We keep HandlerExceptionResolvers in sorted order.AnnotationAwareOrderComparator.sort(this.handlerExceptionResolvers);}}else {try {HandlerExceptionResolver her context.getBean(HANDLER_EXCEPTION_RESOLVER_BEAN_NAME, HandlerExceptionResolver.class);this.handlerExceptionResolvers Collections.singletonList(her);}catch (NoSuchBeanDefinitionException ex) {// Ignore, no HandlerExceptionResolver is fine too.}}// Ensure we have at least some HandlerExceptionResolvers, by registering// default HandlerExceptionResolvers if no other resolvers are found.if (this.handlerExceptionResolvers null) {this.handlerExceptionResolvers getDefaultStrategies(context, HandlerExceptionResolver.class);if (logger.isTraceEnabled()) {logger.trace(No HandlerExceptionResolvers declared in servlet getServletName() : using default strategies from DispatcherServlet.properties);}}}1.1 配置文件DispatcherServlet.properties
org.springframework.web.servlet.HandlerExceptionResolverorg.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver,\org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver1.2 getDefaultStrategies() 如果容器中获取不到 就是在使用了EnableWebMvc和mvc:annotation-driven /后加载的默认的组件还是获取不到的话就会从DispatcherServlet.properties中加载默认的异常处理器。 protected T ListT getDefaultStrategies(ApplicationContext context, ClassT strategyInterface) {String key strategyInterface.getName();String value defaultStrategies.getProperty(key);if (value ! null) {String[] classNames StringUtils.commaDelimitedListToStringArray(value);ListT strategies new ArrayList(classNames.length);for (String className : classNames) {try {Class? clazz ClassUtils.forName(className, DispatcherServlet.class.getClassLoader());Object strategy createDefaultStrategy(context, clazz);strategies.add((T) strategy);}catch (ClassNotFoundException ex) {throw new BeanInitializationException(Could not find DispatcherServlets default strategy class [ className ] for interface [ key ], ex);}catch (LinkageError err) {throw new BeanInitializationException(Unresolvable class definition for DispatcherServlets default strategy class [ className ] for interface [ key ], err);}}return strategies;}else {return new LinkedList();}}1.2.1 createDefaultStrategy() SpringMVC中的几个默认的异常处理器就是经过这个方法但是这个方式创建出来的bean对象是不归Spring管理的。 protected Object createDefaultStrategy(ApplicationContext context, Class? clazz) {return context.getAutowireCapableBeanFactory().createBean(clazz);}0、常见的默认异常处理器
1 SimpleMappingExceptionResolver 基本不用刻意忽略 2 ResponseStatusExceptionResolver 用于处理通过ResponseStatus注解处理的异常 // 实现了接口MessageSourceAware方便拿到国际化资源方便错误消息的国际化
// since 3.0
public class ResponseStatusExceptionResolver extends AbstractHandlerExceptionResolver implements MessageSourceAware {Nullableprivate MessageSource messageSource;Overridepublic void setMessageSource(MessageSource messageSource) {this.messageSource messageSource;}OverrideNullableprotected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response, Nullable Object handler, Exception ex) {try {// 若异常类型是那就处理这个异常// 处理很简单response.sendError(statusCode, resolvedReason)// 当然会有国际化消息的处理。最终new一个空的new ModelAndView()供以返回if (ex instanceof ResponseStatusException) {return resolveResponseStatusException((ResponseStatusException) ex, request, response, handler);}// 若异常类型所在的类上标注了ResponseStatus注解就处理这个状态码//可见异常类型优先于ResponseStatus// 处理方式同上~~~~ResponseStatus status AnnotatedElementUtils.findMergedAnnotation(ex.getClass(), ResponseStatus.class);if (status ! null) {return resolveResponseStatus(status, request, response, handler, ex);}// 这里有个递归如果异常类型是Course里面的也会继续处理所以需要注意这里的递归处理if (ex.getCause() instanceof Exception) {return doResolveException(request, response, handler, (Exception) ex.getCause());}} catch (Exception resolveEx) { // 处理失败就记录warn日志非info哦~if (logger.isWarnEnabled()) {logger.warn(Failure while trying to resolve exception [ ex.getClass().getName() ], resolveEx);}}return null;}
}3 DefaultHandlerExceptionResolver 用于处理Spring MVC自己抛出的一些特定的异常 异常类型状态码MissingPathVariableException500ConversionNotSupportedException500HttpMessageNotWritableException500AsyncRequestTimeoutException503MissingServletRequestParameterException400ServletRequestBindingException400TypeMismatchException400HttpMessageNotReadableException400MethodArgumentNotValidException400MissingServletRequestPartException400BindException400NoHandlerFoundException404HttpRequestMethodNotSupportedException405HttpMediaTypeNotAcceptableException406HttpMediaTypeNotSupportedException415
// since 3.0
public class DefaultHandlerExceptionResolver extends AbstractHandlerExceptionResolver {public DefaultHandlerExceptionResolver() {setOrder(Ordered.LOWEST_PRECEDENCE);setWarnLogCategory(getClass().getName()); // 不同的日志采用不同的记录器是个很好的习惯}OverrideNullableprotected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response, Nullable Object handler, Exception ex) {try {if (ex instanceof HttpRequestMethodNotSupportedException) {return handleHttpRequestMethodNotSupported((HttpRequestMethodNotSupportedException) ex, request, response, handler);} else if (ex instanceof HttpMediaTypeNotSupportedException) {return handleHttpMediaTypeNotSupported((HttpMediaTypeNotSupportedException) ex, request, response, handler);} ... // 省略其它的else if// 多有的handle方法几乎一样的都是response.sendError// 有的还会esponse.setHeader(Accept, MediaType.toString(mediaTypes));等等}
}
4 ExceptionHandlerExceptionResolver 用于处理通过ExceptionHandler注解处理的方法抛出的异常这个异常处理器是用的最多的。 public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExceptionResolverimplements ApplicationContextAware, InitializingBean {。。。。。。。。。。
}4.0 ExceptionHandlerExceptionResolver 继承自AbstractHandlerMethodExceptionResolver该类主要处理Controller中用ExceptionHandler注解定义的方法。 该类也是配置中定义的HandlerExceptionResolver实现类之一大多数异常处理都是由该类操作。 SpringMVC中如果配置了 mvc:annotation-driven/ 或者就会引入的 HandlerExceptionResolverComposite 1、argumentResolvers和customArgumentResolvers是参数解析器负责将HTTP请求数据解析成异常处理方法的形参对象。 2、returnValueHandlers和customReturnValueHandlers是返回值处理器负责将异常处理方法的返回值进行处理。
3、messageConverters是数据转换的底层工具一方面从HTTP请求中读取并转换数据成对象另一方面将对象转成HTTP响应数据。
4、contentNegotiationManager是负责媒体内容的校验即根据Content-Tepe进行不同处理。
5、responseBodyAdvice是ResponseBodyAdvice的缓存即支持在异常处理返回值写到输出流前的切面处理。
6、applicationContext是Spring上下文可以从中获取容器中内容。
7、exceptionHandlerCache是异常-异常处理方法的缓存。
8、exceptionHandlerAdviceCache是ControllerAdvice全局异常处理器的缓存。
4.1 afterPropertiesSet() 在创建这个ExceptionHandlerExceptionResolver对象的时候会执行他的afterPropertiesSet(),在这方法中会去获取ControllerAdvice定义的全局ExceptionHandler方法 Overridepublic void afterPropertiesSet() {// Do this first, it may add ResponseBodyAdvice beans//初始化 ControllerAdvice 的 beaninitExceptionHandlerAdviceCache();if (this.argumentResolvers null) {//获取 默认的参数解析器 DefaultArgumentResolversListHandlerMethodArgumentResolver resolvers getDefaultArgumentResolvers();this.argumentResolvers new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);}if (this.returnValueHandlers null) {//获取 默认的返回值处理器 DefaultReturnValueHandlersListHandlerMethodReturnValueHandler handlers getDefaultReturnValueHandlers();this.returnValueHandlers new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers);}}4.1.1 initExceptionHandlerAdviceCache() 在nitExceptionHandlerAdviceCache()方法中会从Spring容器中获取所有ControllerAdvice标注的bean。遍历这些bean将其中ExceptionHandler标注的异常处理方法缓存到exceptionHandlerAdviceCache。如果这些bean实现了ResponseBodyAdvice接口还会缓存到responseBodyAdvice private void initExceptionHandlerAdviceCache() { // 获取所有ControllerAdvice标注的beanListControllerAdviceBean adviceBeans ControllerAdviceBean.findAnnotatedBeans(getApplicationContext()); for (ControllerAdviceBean adviceBean : adviceBeans) { Class? beanType adviceBean.getBeanType(); if (beanType null) { throw new IllegalStateException(Unresolvable type for ControllerAdviceBean: adviceBean); } // 构造异常-处理方法映射ExceptionHandlerMethodResolver resolver new ExceptionHandlerMethodResolver(beanType); // 添加exceptionHandlerAdviceCache缓存if (resolver.hasExceptionMappings()) { this.exceptionHandlerAdviceCache.put(adviceBean, resolver); } // 添加responseBodyAdvice缓存if (ResponseBodyAdvice.class.isAssignableFrom(beanType)) { this.responseBodyAdvice.add(adviceBean); } }
}4.2 getDefaultArgumentResolvers()
protected ListHandlerMethodArgumentResolver getDefaultArgumentResolvers() {ListHandlerMethodArgumentResolver resolvers new ArrayList();// Annotation-based argument resolutionresolvers.add(new SessionAttributeMethodArgumentResolver());resolvers.add(new RequestAttributeMethodArgumentResolver());// Type-based argument resolutionresolvers.add(new ServletRequestMethodArgumentResolver());resolvers.add(new ServletResponseMethodArgumentResolver());resolvers.add(new RedirectAttributesMethodArgumentResolver());resolvers.add(new ModelMethodProcessor());// Custom arguments//合并了自定义的参数解析器if (getCustomArgumentResolvers() ! null) {resolvers.addAll(getCustomArgumentResolvers());}// Catch-allresolvers.add(new PrincipalMethodArgumentResolver());return resolvers;}
4.3 getDefaultReturnValueHandlers() 获取返回值处理器自此对象创建完成。 protected ListHandlerMethodReturnValueHandler getDefaultReturnValueHandlers() {ListHandlerMethodReturnValueHandler handlers new ArrayList();// Single-purpose return value typeshandlers.add(new ModelAndViewMethodReturnValueHandler());handlers.add(new ModelMethodProcessor());handlers.add(new ViewMethodReturnValueHandler());handlers.add(new HttpEntityMethodProcessor(getMessageConverters(), this.contentNegotiationManager, this.responseBodyAdvice));// Annotation-based return value typeshandlers.add(new ServletModelAttributeMethodProcessor(false));handlers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.contentNegotiationManager, this.responseBodyAdvice));// Multi-purpose return value typeshandlers.add(new ViewNameMethodReturnValueHandler());handlers.add(new MapMethodProcessor());// Custom return value types//合并了自定义的返回值处理器if (getCustomReturnValueHandlers() ! null) {handlers.addAll(getCustomReturnValueHandlers());}// Catch-allhandlers.add(new ServletModelAttributeMethodProcessor(true));return handlers;}二、异常处理流程源码分析
1、DispatcherServlet#processDispatchResult() 在DispatcherServlet#doDispatch()处理请求过程中抛出异常会在DispatcherServlet#processDispatchResult()方法中进行异常处理, 如果监测到了非ModelAndViewDefiningException异常会调用DispatcherServlet#processHandlerException()方法进行异常处理 protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { try { try { // 文件请求处理processedRequest checkMultipart(request); // 请求地址映射mappedHandler getHandler(processedRequest); // 获取处理器适配器HandlerAdapter ha getHandlerAdapter(mappedHandler.getHandler()); // 拦截器预处理if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } // 实际处理请求mv ha.handle(processedRequest, response, mappedHandler.getHandler()); // 拦截器后处理mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { dispatchException ex; } catch (Throwable err) { // As of 4.3, were processing Errors thrown from handler methods as well, // making them available for ExceptionHandler methods and other scenarios. dispatchException new NestedServletException(Handler dispatch failed, err); } // 异常处理processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); }
}
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, Nullable HandlerExecutionChain mappedHandler, Nullable ModelAndView mv, Nullable Exception exception) throws Exception { if (exception ! null) { if (exception instanceof ModelAndViewDefiningException) { logger.debug(ModelAndViewDefiningException encountered, exception); mv ((ModelAndViewDefiningException) exception).getModelAndView(); } else { Object handler (mappedHandler ! null ? mappedHandler.getHandler() : null); mv processHandlerException(request, response, handler, exception); errorView (mv ! null); } }
}
2、processHandlerException() 由于默认初始化添加的是HandlerExceptionResolverComposite处理器,所以执行的也是当前类的resolveException(); protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response, Nullable Object handler, Exception ex) throws Exception { // Check registered HandlerExceptionResolvers... ModelAndView exMv null; if (this.handlerExceptionResolvers ! null) { for (HandlerExceptionResolver resolver : this.handlerExceptionResolvers) { exMv resolver.resolveException(request, response, handler, ex); if (exMv ! null) { break; } } } // ……
}
2.1 HandlerExceptionResolverComposite#resolveException()
public ModelAndView resolveException( HttpServletRequest request, HttpServletResponse response, Nullable Object handler, Exception ex) { if (this.resolvers ! null) { for (HandlerExceptionResolver handlerExceptionResolver : this.resolvers) { ModelAndView mav handlerExceptionResolver.resolveException(request, response, handler, ex); if (mav ! null) { return mav; } } } return null;
}
2.1.1 AbstractHandlerExceptionResolver的resolveException() 先会调用其父类AbstractHandlerExceptionResolver的resolveException()方法 public ModelAndView resolveException( HttpServletRequest request, HttpServletResponse response, Nullable Object handler, Exception ex) { if (shouldApplyTo(request, handler)) { prepareResponse(ex, response); ModelAndView result doResolveException(request, response, handler, ex); if (result ! null) { // Print debug message when warn logger is not enabled. if (logger.isDebugEnabled() (this.warnLogger null || !this.warnLogger.isWarnEnabled())) { logger.debug(buildLogMessage(ex, request) (result.isEmpty() ? : to result)); } // Explicitly configured warn logger in logException method. logException(ex, request); } return result; } else { return null; }
}
2.1.1.1 AbstractHandlerMethodExceptionResolver#doResolveException() 进行类型转换 protected final ModelAndView doResolveException( HttpServletRequest request, HttpServletResponse response, Nullable Object handler, Exception ex) { HandlerMethod handlerMethod (handler instanceof HandlerMethod ? (HandlerMethod) handler : null); return doResolveHandlerMethodException(request, response, handlerMethod, ex);
}
2.1.1.1.1ExceptionHandlerExceptionResolver#doResolveHandlerMethodException() 从缓存中获取异常对应的处理方法添加argumentResolvers和returnValueHandlers。解析异常作为请求参数最后调用异常处理方法进行异常处理。 protected ModelAndView doResolveHandlerMethodException(HttpServletRequest request, HttpServletResponse response, Nullable HandlerMethod handlerMethod, Exception exception) { // 从缓存中获取异常对应的处理方法ServletInvocableHandlerMethod exceptionHandlerMethod getExceptionHandlerMethod(handlerMethod, exception); if (exceptionHandlerMethod null) { return null; } // 添加argumentResolvers和returnValueHandlersif (this.argumentResolvers ! null) { exceptionHandlerMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers); } if (this.returnValueHandlers ! null) { exceptionHandlerMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers); } ServletWebRequest webRequest new ServletWebRequest(request, response); ModelAndViewContainer mavContainer new ModelAndViewContainer(); // 递归添加抛出的异常作为请求参数ArrayListThrowable exceptions new ArrayList(); try { if (logger.isDebugEnabled()) { logger.debug(Using ExceptionHandler exceptionHandlerMethod); } // Expose causes as provided arguments as well Throwable exToExpose exception; while (exToExpose ! null) { exceptions.add(exToExpose); Throwable cause exToExpose.getCause(); exToExpose (cause ! exToExpose ? cause : null); } Object[] arguments new Object[exceptions.size() 1]; exceptions.toArray(arguments); // efficient arraycopy call in ArrayList arguments[arguments.length - 1] handlerMethod; // 调用异常处理方法进行异常处理exceptionHandlerMethod.invokeAndHandle(webRequest, mavContainer, arguments); } catch (Throwable invocationEx) { return null; } if (mavContainer.isRequestHandled()) { return new ModelAndView(); }
} 其中ExceptionHandlerExceptionResolver#getExceptionHandlerMethod方法根据request请求的方法和抛出的异常可以匹配到对应的handleMethod。getExceptionHandlerMethod这个方法可以支持单独使用ExceptionHandler既使用了ExceptionHandler又使用了ControllerAdvice两种方式。 在ExceptionHandlerExceptionResolver#initExceptionHandlerAdviceCache方法中,ExceptionHandlerExceptionResolver已经扫描了所有ControllerAdvice注解的Bean并将其封装成了一个又一个的ExceptionHandlerMethodResolver,而构造ExceptionHandlerMethodResolver时ExceptionHandlerMethodResolver就会扫描这个Bean下所有的ExceptionHandler注解的方法。 所以可以先匹配这个controller是否有使用ExceptionHandler,如果没有则从缓存的ControllerAdviceBean中匹配异常。 2.1.1.1.1.1 ServletInvocableHandlerMethod#getExceptionHandlerMethod()
protected ServletInvocableHandlerMethod getExceptionHandlerMethod(HandlerMethod handlerMethod, Exception exception) {//得到controllerClass? handlerType (handlerMethod ! null ? handlerMethod.getBeanType() : null);if (handlerMethod ! null) {//先尝试从缓存中获取ExceptionHandlerMethodResolver//ExceptionHandlerMethodResolver有缓存所有ExceptionHandler注解的方法ExceptionHandlerMethodResolver resolver this.exceptionHandlerCache.get(handlerType);if (resolver null) {//没获取到的话构造一个并将其放入缓存中resolver new ExceptionHandlerMethodResolver(handlerType);this.exceptionHandlerCache.put(handlerType, resolver);}//根据异常获取对应的handler_method//如果不为空则说明这个controoler配置了ExceptionHandlerMethod method resolver.resolveMethod(exception);if (method ! null) {return new ServletInvocableHandlerMethod(handlerMethod.getBean(), method);}}//如果controller没有配置ExceptionHandler,则使用统一配置的ControllerAdvice//遍历所有的ControllerAdvice,根据异常匹配对应的handler_methodfor (EntryControllerAdviceBean, ExceptionHandlerMethodResolver entry : this.exceptionHandlerAdviceCache.entrySet()) {if (entry.getKey().isApplicableToBeanType(handlerType)) {ExceptionHandlerMethodResolver resolver entry.getValue();Method method resolver.resolveMethod(exception);//如果匹配倒了返回这个methodif (method ! null) {return new ServletInvocableHandlerMethod(entry.getKey().resolveBean(), method);}}}return null;
}
2.1.1.1.1.2 ServletInvocableHandlerMethod#invokeAndHandle() 和之前的HandleMapping一眼的处理流程 public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {//调用反射handler_method拿到handler_method执行的结果returnValueObject returnValue invokeForRequest(webRequest, mavContainer, providedArgs);//如果这个handler_method上还标注了ResponseStatus注解//设置response的http状态码和错误原因setResponseStatus(webRequest);//将执行结果保存到ModelAndViewContainer中if (returnValue null) {if (isRequestNotModified(webRequest) || hasResponseStatus() || mavContainer.isRequestHandled()) {mavContainer.setRequestHandled(true);return;}}else if (StringUtils.hasText(this.responseReason)) {mavContainer.setRequestHandled(true);return;}mavContainer.setRequestHandled(false);try {//处理执行的返回值this.returnValueHandlers.handleReturnValue(returnValue, getReturnValueType(returnValue), mavContainer, webRequest);}catch (Exception ex) {if (logger.isTraceEnabled()) {logger.trace(getReturnValueHandlingErrorMessage(Error handling return value, returnValue), ex);}throw ex;}
}3、总结流程 1、ExceptionHandlerExceptionResolver根据请求的方法和抛出的异常匹配对应的异常处理方法 2、先匹配controller中有的ExceptionHandler标注了的方法 3、再匹配ControllerAdvice中的ExceptionHandler标注的方法 4、执行异常处理方法获取返回值 5、返回值输出到response中
