spring mvc请求照射关系处理

spring mvc请求映射关系处理
1：看DispatcherServlet的初始化策略

protected void initStrategies(ApplicationContext context) {initMultipartResolver(context);initLocaleResolver(context);initThemeResolver(context);//初始化处理器映射关系，即用户请求与程序处理的对应关系initHandlerMappings(context);initHandlerAdapters(context);initHandlerExceptionResolvers(context);initRequestToViewNameTranslator(context);initViewResolvers(context);}//initHandlerMappings默认会先探测ApplicationContext对象中已经设定好的任何HandlerMapping对象，如果有就使用定义好的，如果没有，调用方法getDefaultStrategies，使用默认配置，DisptatchServlet.properties文件中默认的org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping两个HandlerMapping对象。

2：看下DefaultAnnotationHandlerMapping类层次关系，BeanNameUrlHandlerMapping类层次是一样的

//类层次，凑合看DefaultAnnotationHandlerMappingAbstractDetectingUrlHandlerMappingAbstractUrlHandlerMappingAbstractHandlerMappingextends WebApplicationObjectSupport implements HandlerMapping, Ordered//这里继承了WebApplicationObjectSupport对象，关于这个对象：Convenient superclass for application objects running in a WebApplicationContext.WebApplicationObjectSupportextends ApplicationObjectSupport implements ServletContextAwareimplements ApplicationContextAware

3：抽象类ApplicationObjectSupport实现了ApplicationContextAware，spring容器的后置处理器会调用setApplicationContext方法，执行顺序：

//ApplicationObjectSupport中的setApplicationContext方法执行public final void setApplicationContext(ApplicationContext context) throws BeansException {if (context == null && !isContextRequired()) {// Reset internal context state.this.applicationContext = null;this.messageSourceAccessor = null;}else if (this.applicationContext == null) {// Initialize with passed-in context.if (!requiredContextClass().isInstance(context)) {throw new ApplicationContextException("Invalid application context: needs to be of type [" + requiredContextClass().getName() + "]");}this.applicationContext = context;this.messageSourceAccessor = new MessageSourceAccessor(context);//这里会先执行子类WebApplicationObjectSupport的initApplicationContext方法，然后到ApplicationObjectSupport自己的init方法，ApplicationObjectSupport本身的该方法没有任何处理，只是调用了一个空的方法initApplicationContext()，这个无参的重载方法被当作一个钩子供子类方法来实现。initApplicationContext(context);}else {// Ignore reinitialization if same context passed in.if (this.applicationContext != context) {throw new ApplicationContextException("Cannot reinitialize with different application context: current one is [" +this.applicationContext + "], passed-in one is [" + context + "]");}}}

4：initApplicationContext()执行，spring默认的两个处理器映射类都继承自AbstractDetectingUrlHandlerMapping抽象类，而且类初始化将被执行的initApplicationContext方法也在这个类得到了实现

//AbstractDetectingUrlHandlerMapping中的initApplicationContext方法public void initApplicationContext() throws ApplicationContextException {//先执行超类的initApplicationContext方法，这个超类的方法完成的任务就是对定义好的拦截器改装并放入到adaptedInterceptors数组中供以后使用super.initApplicationContext();//请求与处理器映射的关键方法detectHandlers();}

5：detectHandlers()执行

protected void detectHandlers() throws BeansException {if (logger.isDebugEnabled()) {logger.debug("Looking for URL mappings in application context: " + getApplicationContext());}//默认会取得上下文中的所有的对象的beanname。String[] beanNames = (this.detectHandlersInAncestorContexts ?BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :getApplicationContext().getBeanNamesForType(Object.class));// Take any bean name that we can determine URLs for.for (int i = 0; i < beanNames.length; i++) {String beanName = beanNames[i];//abstract方法，在子类中实现，即找到符合要求的映射urlString[] urls = determineUrlsForHandler(beanName);if (!ObjectUtils.isEmpty(urls)) {// URL paths found: Let's consider it a handler.//注册处理器，即添加一些映射关系到handlerMap中，一个LinkedHashMapregisterHandler(urls, beanName);}else {if (logger.isDebugEnabled()) {logger.debug("Rejected bean name '" + beanNames[i] + "': no URL paths identified");}}}}

6：determineUrlsForHandler方法执行，DefaultAnnotationHandlerMapping为例子

不贴了，主要就是挨个对象查看，DefaultAnnotationHandlerMapping类就是查看定义的RequestMapping注解，然后把符合要求的urls返回。

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