@ConfigurationProperties(
    prefix = "spring.resources",
    ignoreUnknownFields = false
)
public class ResourceProperties {
    可以設定和靜態資源有關的引數(快取時間等)--->和下面的：Duration cachePeriod = this.resourceProperties.getCache().getPeriod();對應起來！
}

public void addResourceHandlers(ResourceHandlerRegistry registry) {
    if (!this.resourceProperties.isAddMappings()) {
        logger.debug("Default resource handling disabled");
    } else {
        Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
        CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
        if (!registry.hasMappingForPattern("/webjars/**")) {
            //所有的/webjars/**，都去classpath：META-INF/resources/webjar找資源
            this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{"/webjars/**"})
            .addResourceLocations(new String[]{"classpath:/META-INF/resources/webjars/"})
            .setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
        }

        String staticPathPattern = this.mvcProperties.getStaticPathPattern();
        if (!registry.hasMappingForPattern(staticPathPattern)) {
            this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{staticPathPattern}).addResourceLocations(WebMvcAutoConfiguration.getResourceLocations(this.resourceProperties.getStaticLocations())).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
        }

    }
}
 

1.所有的/webjars/**(所有請求)，都去classpath：META-INF/resources/webjar找資源

訪問路徑：localhost:8080/webjars/jquery/3.5.1/jquery.js可以訪問到jquery的webjar中的內容！
<!--引入jquery的webjar-->  在訪問時只需要寫webjars下面的資源的名稱即可！
<dependency>
    <groupId>org.webjars</groupId>
    <artifactId>jquery</artifactId>
    <version>3.5.1</version>
</dependency>
 

2."/**"訪問當前專案的任何資源：(靜態資源的儲存資料夾)

分析原始碼得知：當訪問當前專案的任何資源時：會去當前類路徑下的以下資料夾進行查詢：
"classpath:/META-INF/resources/", 
"classpath:/resources/", 
"classpath:/static/", 
"classpath:/public/"
"/":當前專案的根路徑

當訪問路徑是：localhost:8080/abc=====>去靜態資原始檔夾中找abc

3.歡迎頁的對映

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

歡迎頁：靜態資原始檔夾下的所有index.html頁面；被"/**"對映
當訪問路徑是：localhost:8080/  會去靜態檔案資源夾中找index.html