<dependency>
   <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-configuration-processor</artifactId>
   <optional>true</optional>
</dependency>

@EnableConfigurationProperties({WebMvcProperties.class, WebProperties.class})

//ResourceProperties resourceProperties --> 獲取和spring.resources綁定的所有的值的對象
//WebMvcProperties mvcProperties --> 獲取和spring.mvc綁定的所有的值的對象
//ListableBeanFactory beanFactory --> Spring的beanFactory
//HttpMessageConverters --> 找到所有的HttpMessageConverters
//ResourceHandlerRegistrationCustomizer --> 找到資源處理器的自定義(重點(diǎn)解析)
//DispatcherServletPath -->  找到資源的路徑
//ServletRegistrationBean --> 給應(yīng)用注冊Servlet、Filter....
public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties, WebMvcProperties mvcProperties,
			ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider,
			ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
			ObjectProvider<DispatcherServletPath> dispatcherServletPath,
			ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
	this.resourceProperties = resourceProperties;
	this.mvcProperties = mvcProperties;
	this.beanFactory = beanFactory;
	this.messageConvertersProvider = messageConvertersProvider;
	this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
	this.dispatcherServletPath = dispatcherServletPath;
	this.servletRegistrations = servletRegistrations;
}

public void addResourceHandlers(ResourceHandlerRegistry registry) {
	// 判斷resource.add-mappings的值true/false(默認(rèn)為true,可以在配置文件修改配置項(xiàng))
	if (!this.resourceProperties.isAddMappings()) {
		// resource.add-mappings的值為false，則禁用所有的靜態(tài)資源的訪問規(guī)則，debug日志輸出下面這句話
		logger.debug("Default resource handling disabled");
		return;
	}

	// resource.add-mappings的值true的話，定義規(guī)則

	// 定義緩存的相關(guān)配置
	Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
	CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
	// 定義webjars的資源存儲規(guī)則和緩存時(shí)間
    if (!registry.hasMappingForPattern("/webjars/**")) {
		customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**")
			.addResourceLocations("classpath:/META-INF/resources/webjars/")
			.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
	}
	         
	// 定義靜態(tài)資源的訪問規(guī)則
	// this.mvcProperties.getStaticPathPattern() --> 獲取靜態(tài)資源的訪問方式，默認(rèn)是\/**
	String staticPathPattern = this.mvcProperties.getStaticPathPattern();
	if (!registry.hasMappingForPattern(staticPathPattern)) {
		customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern)
			// getStaticLocations()方法中
			.addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations()))
			.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
	}
}

@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext, FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
	// 下面 welcomePageHandlerMapping 的有參函數(shù)在下面圖片
    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;
}