Spirng 源代码学习笔记 Web 篇（2）HandlerMapping

Spirng 源代码学习笔记 Web 篇（二）HandlerMapping
org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping

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继承结构：

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HandlerMapping

接口声明如下，入参为 request 对象，返回为?HandlerExecutionChain。?

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HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;

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HandlerExecutionChain 包含实际处理请求的对象和拦截器。实际处理请求的对象例子是普通的 Controller 对象；拦截器的例子：如对 http 返回设置统一的防止浏览器缓存头信息。

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AbstractHandlerMapping

继承自 WebApplicationObjectSupport，支持 ordering, a default handler, and handler interceptors.

使用 template method:

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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 = getApplicationContext().getBean(handlerName);}return getHandlerExecutionChain(handler, request);}protected abstract Object getHandlerInternal(HttpServletRequest request) throws Exception;protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {if (handler instanceof HandlerExecutionChain) {HandlerExecutionChain chain = (HandlerExecutionChain) handler;chain.addInterceptors(getAdaptedInterceptors());return chain;}else {return new HandlerExecutionChain(handler, getAdaptedInterceptors());}}

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AbstractUrlHandlerMapping

for URL-mapped。Provides infrastructure for mapping handlers to URLs;

Supports direct matches and various Ant-style pattern matches。

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// 注册映射关系

protected void registerHandler(String urlPath, Object handler)

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// 根据已注册的映射集合找到所有匹配项，并确定一个 best match

protected Object lookupHandler(String urlPath, HttpServletRequest request)

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// 调用 lookupHandler，设置拦截器，返回 HandlerExecutionChain

protected Object getHandlerInternal(HttpServletRequest request)

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SimpleUrlHandlerMapping

根据用户配置的 Map<String, Object> 集合，注册映射集合。

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AbstractDetectingUrlHandlerMapping

扫描所有 spring 上下文中的 bean 实例，存在映射的自动进行注册。

再次 template method:

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protected void detectHandlers() throws BeansException {if (logger.isDebugEnabled()) {logger.debug("Looking for URL mappings in application context: " + getApplicationContext());}String[] beanNames = (this.detectHandlersInAncestorContexts ?BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :getApplicationContext().getBeanNamesForType(Object.class));// Take any bean name that we can determine URLs for.for (String beanName : beanNames) {String[] urls = determineUrlsForHandler(beanName);if (!ObjectUtils.isEmpty(urls)) {// URL paths found: Let's consider it a handler.registerHandler(urls, beanName);}else {if (logger.isDebugEnabled()) {logger.debug("Rejected bean name '" + beanName + "': no URL paths identified");}}}}protected abstract String[] determineUrlsForHandler(String beanName);

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BeanNameUrlHandlerMapping

beanName 映射，只处理以 “/” 开始的 beanName。

protected String[] determineUrlsForHandler(String beanName) {List<String> urls = new ArrayList<String>();if (beanName.startsWith("/")) {urls.add(beanName);}String[] aliases = getApplicationContext().getAliases(beanName);for (String alias : aliases) {if (alias.startsWith("/")) {urls.add(alias);}}return StringUtils.toStringArray(urls);}

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DefaultAnnotationHandlerMapping

类和方法上 RequestMapping 注解中的 value 值作为 url 的构成部分。

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AbstractControllerUrlHandlerMapping

基于约定，面向 Controller 类型的映射。可配置不希望包含的类或者包。

Controller 类型是指实现了 org.springframework.web.servlet.mvc.Controller 接口或者类上使用了 @Controller 注解。

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ControllerBeanNameHandlerMapping

根据 beanName 和配置的前缀、后缀作为映射的 url。

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ControllerClassNameHandlerMapping

根据类的名称生成 url，可配置大小写敏感、路径前缀、basePackage。

org.springframework.web.servlet.mvc.Controller

WelcomeController -> /welcome*HomeController -> /home*

For MultiActionControllers and @Controller beans

WelcomeController -> /welcome, /welcome/*CatalogController -> /catalog, /catalog/*