158_SpringBoot_web请求映射原理

所有的请求映射都在HandlerMapping中
SpringBoot自动配置欢迎页的 WelcomePageHandlerMapping 。访问 /能访问到index.html；
SpringBoot自动配置了默认 的 RequestMappingHandlerMapping
请求进来，挨个尝试所有的HandlerMapping看是否有请求信息
如果找到这个请求对应的handler 如没有就是下一个 HandlerMapping
我们需要一些自定义的映射处理，我们也可以自己给容器中放HandlerMapping。自定义 HandlerMapping

WebMvcAutoConfiguration -RequestMappingHandlerMapping 自动扫描+注册 所有controller中标注了@RequestMapping

        @Bean
        @Primary
        public RequestMappingHandlerMapping requestMappingHandlerMapping(@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager contentNegotiationManager, @Qualifier("mvcConversionService") FormattingConversionService conversionService, @Qualifier("mvcResourceUrlProvider") ResourceUrlProvider resourceUrlProvider) {
            return super.requestMappingHandlerMapping(contentNegotiationManager, conversionService, resourceUrlProvider);
        }

        @Bean
        public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext, FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
            WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(new TemplateAvailabilityProviders(applicationContext), applicationContext, this.getWelcomePage(), this.mvcProperties.getStaticPathPattern());
            welcomePageHandlerMapping.setInterceptors(this.getInterceptors(mvcConversionService, mvcResourceUrlProvider));
            welcomePageHandlerMapping.setCorsConfigurations(this.getCorsConfigurations());
            return welcomePageHandlerMapping;
        }

匹配具体路径的流程 SpringMVC功能分析都从 org.springframework.web.servlet.DispatcherServlet -> doDispatch

1  获取request

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);

				// 找到当前请求使用哪个Handler（Controller的方法）处理
				mappedHandler = getHandler(processedRequest);
                
                //HandlerMapping：处理器映射。/xxx->>xxxx
				

debug 进入 mappedHandler = this.getHandler(processedRequest);

    @Nullable
    protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
        if (this.handlerMappings != null) {
            Iterator var2 = this.handlerMappings.iterator();

            while(var2.hasNext()) {
                HandlerMapping mapping = (HandlerMapping)var2.next();
                HandlerExecutionChain handler = mapping.getHandler(request);
                if (handler != null) {
                    return handler;
                }
            }
        }
		
		

2  RequestMappingHandlerMapping：保存了所有@RequestMapping 和handler的映射规则