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springmvc path请求映射到bean 方法的流程

时间:2021-10-21 10:17     来源/作者:乘风破浪的码农

一、加载注册流程

1.在dispatch-servlet.xml中配置,在控制器的方法上加入@RequestMapping注解即可。

2.mvc:annotation-driven的解析流程 会调用到自定义元素解析器的AnnotationDrivenBeanDefinitionParser.parse方法。

3.org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping为RequestMapping注解映射到后台接口的注册表。此类实现了InitializingBean接口,会触发到

afterPropertiesSet方法。

 org.springframework.web.servlet.handler.AbstractHandlerMethodMapping @Override public void afterPropertiesSet() { initHandlerMethods(); } /** * Scan beans in the ApplicationContext, detect and register handler methods. * @see #getCandidateBeanNames() * @see #processCandidateBean * @see #handlerMethodsInitialized */ protected void initHandlerMethods() { for (String beanName : getCandidateBeanNames()) { if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) { processCandidateBean(beanName); } } handlerMethodsInitialized(getHandlerMethods()); }

4.在initHandlerMethods方法中会先调用getCandidateBeanNames获取当前容器工厂的所有BEAN,然后逐个BEAN进行处理。

4.1 获取所有BEAN流程

 protected String[] getCandidateBeanNames() { return (this.detectHandlerMethodsInAncestorContexts ? BeanFactoryUtils.beanNamesForTypeIncludingAncestors(obtainApplicationContext(), Object.class) : obtainApplicationContext().getBeanNamesForType(Object.class)); }

4.2 处理BEAN流程

 protected void processCandidateBean(String beanName) { Class beanType = null; try { beanType = obtainApplicationContext().getType(beanName); } catch (Throwable ex) { // An unresolvable bean type, probably from a lazy bean - let's ignore it. if (logger.isTraceEnabled()) { logger.trace("Could not resolve type for bean '" + beanName + "'", ex); } } if (beanType != null && isHandler(beanType)) { detectHandlerMethods(beanName); } }

4.3 判断当前BEAN是否HANDLER

 protected boolean isHandler(Class{C} beanType) { return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) || AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class)); }

4.4 如果此类是控制器或者有requestMapping注解,才会处理。

springmvc path请求映射到bean 方法的流程

4.5 遍历当前类的所有方法,查找包含RequestMapping注解的方法,然后保存到

AbstractHandlerMethodMapping.MappingRegistry注册表中。

 protected void detectHandlerMethods(Object handler) { Class{C} handlerType = (handler instanceof String ? obtainApplicationContext().getType((String) handler) : handler.getClass()); if (handlerType != null) { Class{C} userType = ClassUtils.getUserClass(handlerType); Map methods = MethodIntrospector.selectMethods(userType, (MethodIntrospector.MetadataLookup) method -> { try { return getMappingForMethod(method, userType); } catch (Throwable ex) { throw new IllegalStateException("Invalid mapping on handler class [" + userType.getName() + "]: " + method, ex); } }); if (logger.isTraceEnabled()) { logger.trace(formatMappings(userType, methods)); } methods.forEach((method, mapping) -> { Method invocableMethod = AopUtils.selectInvocableMethod(method, userType); registerHandlerMethod(handler, invocableMethod, mapping); }); } }

判断当前方法是否包含requestMapping注解

 private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) { RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class); RequestCondition{C} condition = (element instanceof Class ? getCustomTypeCondition((Class{C}) element) : getCustomMethodCondition((Method) element)); return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null); }

最终会调用org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.registerHandlerMethod保存到URL和RequestMappinfo的映射注册表中。

 AbstractHandlerMethodMapping protected void registerHandlerMethod(Object handler, Method method, T mapping) { this.mappingRegistry.register(mapping, handler, method); }

具体的保存逻辑

在这个方法中主要操作的数据对象有四个,分别是mappingLookup、urlLookup、corsLookup和registry。下面对这四个对象进行说明:

  1. mappingLookup对象是Map结构,key表示mapping对象,value表示处理对象,在本例中key是RequestMappingInfo对象,value是Controller中的某一个方法。
  2. urlLookup对象是Map结构,key表示url,value表示mapping对象,本例中key是具体的url值"/demo/postMapping/",value是RequestMappingInfo对象,
  3. corsLookup对象是Map结构,key表示处理方法(Controller中的某个方法),value表示跨域配置,本例中没有进行跨域注解的使用因此数据不存在,如果需要看到跨域数据,可以在method上添加@CrossOrigin注解
  4. registry对象是Map结构,key表示mapping对象,value表示MappingRegistration对象
 AbstractHandlerMethodMapping.MappingRegistry  内部类 public void register(T mapping, Object handler, Method method) { this.readWriteLock.writeLock().lock(); try { HandlerMethod handlerMethod = createHandlerMethod(handler, method); validateMethodMapping(handlerMethod, mapping); this.mappingLookup.put(mapping, handlerMethod); List directUrls = getDirectUrls(mapping); for (String url : directUrls) { this.urlLookup.add(url, mapping); } String name = null; if (getNamingStrategy() != null) { name = getNamingStrategy().getName(handlerMethod, mapping); addMappingName(name, handlerMethod); } this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name)); } finally { this.readWriteLock.writeLock().unlock(); } }

生成的数据如下:

springmvc path请求映射到bean 方法的流程

5.系统拦截器列表初始化过程,会调用到AbstractHandlerMapping.initApplicationContext,这个会查找当前容器工厂中所有继承了MappedInterceptor类的拦截器实例BEAN.然后保存到AbstractHandlerMapping.interceptors

 protected void initApplicationContext() throws BeansException { extendInterceptors(this.interceptors); detectMappedInterceptors(this.adaptedInterceptors); initInterceptors(); }

springmvc path请求映射到bean 方法的流程

二、调用HTTP请求根据PATH寻找接口方法流程

1.首先tomcat会调用DispatcherServlet.doDispatch方法,进行请求分发处理。

 protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { HttpServletRequest processedRequest = request; HandlerExecutionChain mappedHandler = null; boolean multipartRequestParsed = false; WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); try { ModelAndView mv = null; Exception dispatchException = null; try { processedRequest = checkMultipart(request); multipartRequestParsed = (processedRequest != request); // Determine handler for the current request. mappedHandler = getHandler(processedRequest); if (mappedHandler == null) { noHandlerFound(processedRequest, response); return; } // Determine handler adapter for the current request. HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } // Actually invoke the handler. mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; } applyDefaultViewName(processedRequest, mv); mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { dispatchException = ex; } processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } finally { if (asyncManager.isConcurrentHandlingStarted()) { // Instead of postHandle and afterCompletion if (mappedHandler != null) { mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response); } } else { // Clean up any resources used by a multipart request. if (multipartRequestParsed) { cleanupMultipart(processedRequest); } } } }

2.首先调用getHandler去根据请求PATH查找HandlerExecutionChain,HandlerExecutionChain就是一个RequestHandleMappinfo加上一个拦截器列表。会调用到AbstractHandlerMapping.getHandler

 public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { Object handler = getHandlerInternal(request); if (handler == null) { handler = getDefaultHandler(); } if (handler == null) { return null; } // Bean name or resolved handler? if (handler instanceof String) { String handlerName = (String) handler; handler = obtainApplicationContext().getBean(handlerName); } HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request); return executionChain; }

3.最终会调用到AbstractHandlerMapping.lookupHandlerMethod根据PATH查找HandlerMethod,这里面的 this.mappingRegistry.getMappingsByUrl就是初始化时的URL和RequestMappingInfo映射表。

 protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception { List matches = new ArrayList<>(); List directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath); if (directPathMatches != null) { addMatchingMappings(directPathMatches, matches, request); } if (matches.isEmpty()) { // No choice but to go through all mappings... addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request); } if (!matches.isEmpty()) { Match bestMatch = matches.get(0); request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.handlerMethod); handleMatch(bestMatch.mapping, lookupPath, request); return bestMatch.handlerMethod; } else { return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request); } }

调用堆栈1

springmvc path请求映射到bean 方法的流程

调用堆栈2

springmvc path请求映射到bean 方法的流程 4.

初始化HandlerExecutionChain拦截器列表,这个会查找当前容器工厂中所有实现了handleInteropr 的类,

 AbstractHandlerMapping类 protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) { HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ? (HandlerExecutionChain) handler : new HandlerExecutionChain(handler)); String lookupPath = this.urlPathHelper.getLookupPathForRequest(request, LOOKUP_PATH); for (HandlerInterceptor interceptor : this.adaptedInterceptors) { if (interceptor instanceof MappedInterceptor) { MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor; if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) { chain.addInterceptor(mappedInterceptor.getInterceptor()); } } else { chain.addInterceptor(interceptor); } } return chain; }

springmvc path请求映射到bean 方法的流程

这个类会根据拦截器的URL匹配规则相应添加拦截器列表。

   

5.调用所有拦截器的applyPreHandle方法

 boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception { HandlerInterceptor[] interceptors = getInterceptors(); if (!ObjectUtils.isEmpty(interceptors)) { for (int i = 0; i 

7.然后调用invocableMethod.invokeAndHandle(webRequest, mavContainer),首先通过反射调用handlerMethod中的bean的接口方法

 ServletInvocableHandlerMethod public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs); setResponseStatus(webRequest); if (returnValue == null) { if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) { disableContentCachingIfNecessary(webRequest); mavContainer.setRequestHandled(true); return; } } else if (StringUtils.hasText(getResponseStatusReason())) { mavContainer.setRequestHandled(true); return; } mavContainer.setRequestHandled(false); Assert.state(this.returnValueHandlers != null, "No return value handlers"); try { this.returnValueHandlers.handleReturnValue( returnValue, getReturnValueType(returnValue), mavContainer, webRequest); } catch (Exception ex) { if (logger.isTraceEnabled()) { logger.trace(formatErrorForReturnValue(returnValue), ex); } throw ex; } }

springmvc path请求映射到bean 方法的流程

9.最后调用HandlerMethodReturnValueHandlerComposite.handleReturnValue 进行返回值处理,例如将BEAN转JSON,转XML等。

9.1 这个找HANDLER的过程也是,根据此HANDLER是否支持此方法,如在方法上加上了@ResponseBody,则会由RequestResponseBodyMethodProcessor处理。

 RequestResponseBodyMethodProcessor public boolean supportsReturnType(MethodParameter returnType) { return (AnnotatedElementUtils.hasAnnotation(returnType.getContainingClass(), ResponseBody.class) || returnType.hasMethodAnnotation(ResponseBody.class)); }
 public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception { HandlerMethodReturnValueHandler handler = selectHandler(returnValue, returnType); if (handler == null) { throw new IllegalArgumentException("Unknown return value type: " + returnType.getParameterType().getName()); } handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest); }

springmvc path请求映射到bean 方法的流程

 RequestResponseBodyMethodProcessor。 此类继承了AbstractMessageConverterMethodProcessor,这个类会调用当前容器工厂中所有

springmvc path请求映射到bean 方法的流程

9.2 由于我们在方法上加了@ResponseBody注解,所有此handler为

 protected  void writeWithMessageConverters(@Nullable T value, MethodParameter returnType, ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage) throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException { Object body; Class{C} valueType; Type targetType; if (value instanceof CharSequence) { body = value.toString(); valueType = String.class; targetType = String.class; } else { body = value; valueType = getReturnValueType(body, returnType); targetType = GenericTypeResolver.resolveType(getGenericType(returnType), returnType.getContainingClass()); } if (selectedMediaType != null) { selectedMediaType = selectedMediaType.removeQualityValue(); for (HttpMessageConverter{C} converter : this.messageConverters) { GenericHttpMessageConverter genericConverter = (converter instanceof GenericHttpMessageConverter ? (GenericHttpMessageConverter{C}) converter : null); if (genericConverter != null ? ((GenericHttpMessageConverter) converter).canWrite(targetType, valueType, selectedMediaType) : converter.canWrite(valueType, selectedMediaType)) { body = getAdvice().beforeBodyWrite(body, returnType, selectedMediaType, (Class{C}>) converter.getClass(), inputMessage, outputMessage); if (body != null) { Object theBody = body; LogFormatUtils.traceDebug(logger, traceOn -> "Writing [" + LogFormatUtils.formatValue(theBody, !traceOn) + "]"); addContentDispositionHeader(inputMessage, outputMessage); if (genericConverter != null) { genericConverter.write(body, targetType, selectedMediaType, outputMessage); } else { ((HttpMessageConverter) converter).write(body, selectedMediaType, outputMessage); } } else { if (logger.isDebugEnabled()) { logger.debug("Nothing to write: null body"); } } return; } } } }

springmvc path请求映射到bean 方法的流程

9.3 messageConverts的数据初始化来源为 RequestMappingHandlerAdapter.getDefaultArgumentResolvers方法中,

 resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice));

messageConverts来源于RequestMappingHandlerAdapter.messageConverters中。

在初始化时会,依赖注入当前系统中所有的messageConvert.

springmvc path请求映射到bean 方法的流程

10.最后调用拦截器的所有postHandle方法进行,处理完回调。

 void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv) throws Exception { HandlerInterceptor[] interceptors = getInterceptors(); if (!ObjectUtils.isEmpty(interceptors)) { for (int i = interceptors.length - 1; i >= 0; i--) { HandlerInterceptor interceptor = interceptors[i]; interceptor.postHandle(request, response, this.handler, mv); } } }

11.在渲染完输出视图后,会调用所有拦截器的afterCompletion方法,注意,JSON,XML这种没有视图,只有HTML等才有。

 void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex) throws Exception { HandlerInterceptor[] interceptors = getInterceptors(); if (!ObjectUtils.isEmpty(interceptors)) { for (int i = this.interceptorIndex; i >= 0; i--) { HandlerInterceptor interceptor = interceptors[i]; try { interceptor.afterCompletion(request, response, this.handler, ex); } catch (Throwable ex2) { logger.error("HandlerInterceptor.afterCompletion threw exception", ex2); } } } }

springmvc path请求映射到bean 方法的流程

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原文链接:https://blog.csdn.net/lipengyao2010/article/details/118941496

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