所以,加了这个注解,就会有一写初始化的操作
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
}
导入了DelegatingWebMvcConfiguration  extends WebMvcConfigurationSupport{// WebMvcConfigurerComposite implements WebMvcConfigurer// WebMvcConfigurerComposite实现了WebMvcConfigurer接口,同时还持有多个List<WebMvcConfigurer>private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();{// WebMvcConfigurer配置相关的类private final List<WebMvcConfigurer> delegates = new ArrayList<>();// 下列方法都是调用当前持有的所有WebMvcConfigurer对应的方法public void addWebMvcConfigurers(List<WebMvcConfigurer> configurers) {if (!CollectionUtils.isEmpty(configurers)) {this.delegates.addAll(configurers);}}@Overridepublic void addInterceptors(InterceptorRegistry registry) {for (WebMvcConfigurer delegate : this.delegates) {delegate.addInterceptors(registry);}}public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {for (WebMvcConfigurer delegate : this.delegates) {delegate.configureMessageConverters(converters);}}@Overridepublic void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) {for (WebMvcConfigurer delegate : this.delegates) {delegate.addReturnValueHandlers(returnValueHandlers);}}}// WebMvcConfigurerComposite是通过set注入的方式,将Spring容器中WebMvcConfigurer类型的bean都注入@Autowired(required = false)public void setConfigurers(List<WebMvcConfigurer> configurers) {if (!CollectionUtils.isEmpty(configurers)) {this.configurers.addWebMvcConfigurers(configurers);}}// 注入bean,RequestMappingHandlerMappingpublic RequestMappingHandlerMapping requestMappingHandlerMapping(){RequestMappingHandlerMapping mapping = createRequestMappingHandlerMapping();mapping.setOrder(0);mapping.setInterceptors(getInterceptors(conversionService, resourceUrlProvider){if (this.interceptors == null) {InterceptorRegistry registry = new InterceptorRegistry();// 执行WebMvcConfigurerComposite的添加拦截器方法addInterceptors(registry);// 注册两个拦截器registry.addInterceptor(new ConversionServiceExposingInterceptor(mvcConversionService));registry.addInterceptor(new ResourceUrlProviderExposingInterceptor(mvcResourceUrlProvider));// 将所有拦截器进行遍历,如果有设置了includePatterns或者excludePatterns,则包装成MappedInterceptorthis.interceptors = registry.getInterceptors();{return this.registrations.stream().sorted(INTERCEPTOR_ORDER_COMPARATOR).map(InterceptorRegistration::getInterceptor){if (this.includePatterns == null && this.excludePatterns == null) {return this.interceptor;}MappedInterceptor mappedInterceptor = new MappedInterceptor(StringUtils.toStringArray(this.includePatterns),StringUtils.toStringArray(this.excludePatterns),this.interceptor);if (this.pathMatcher != null) {mappedInterceptor.setPathMatcher(this.pathMatcher);}return mappedInterceptor;}.collect(Collectors.toList());}}return this.interceptors.toArray();});// 设置跨域配置// 执行所有WebMvcConfigurer中的addCorsMappingsmapping.setCorsConfigurations(getCorsConfigurations());// 其他设置return mapping;}@Beanpublic RequestMappingHandlerAdapter requestMappingHandlerAdapter(){// 创建对象RequestMappingHandlerAdapter adapter = createRequestMappingHandlerAdapter();// 设置消息转换器// 同时执行所有WebMvcConfigurer的configureMessageConverters和extendMessageConverters// 如果没有,根据导包给一些默认的转换器adapter.setMessageConverters(getMessageConverters());// 设置WebBinder初始化器 ConfigurableWebBindingInitializeradapter.setWebBindingInitializer(getConfigurableWebBindingInitializer(conversionService, validator));// 设置自定义的参数解析器,同时执行所有WebMvcConfigurer的addArgumentResolversadapter.setCustomArgumentResolvers(getArgumentResolvers());// 设置自定义的返回值处理器,同时执行所有WebMvcConfigurer的addReturnValueHandlersadapter.setCustomReturnValueHandlers(getReturnValueHandlers());// 如果存在json,添加两个JsonViewRequestBodyAdvice,JsonViewResponseBodyAdviceif (jackson2Present) {adapter.setRequestBodyAdvice(Collections.singletonList(new JsonViewRequestBodyAdvice()));adapter.setResponseBodyAdvice(Collections.singletonList(new JsonViewResponseBodyAdvice()));}// 添加两个返回异步结果的拦截器adapter.setCallableInterceptors(configurer.getCallableInterceptors());adapter.setDeferredResultInterceptors(configurer.getDeferredResultInterceptors());return adapter;}// 等等等等其他组件,视图解析器,语言解析器,异常解析器
}