一、原理

public void addResourceHandlers(ResourceHandlerRegistry registry) {
            if (!this.resourceProperties.isAddMappings()) {
                logger.debug("Default resource handling disabled");
            } else {
                Integer cachePeriod = this.resourceProperties.getCachePeriod();
                if (!registry.hasMappingForPattern("/webjars/**")) {
                    this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{"/webjars/**"}).addResourceLocations(new String[]{"classpath:/META-INF/resources/webjars/"}).setCachePeriod(cachePeriod));
                }

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

            }
        }

二、引入外部的静态文件

1）、所有/webjars/**，都去"classpath:/META-INF/resources/webjars/"找资源
webjars：以jar包的方式引入静态资源
2）、如何导入webjars

在这里插入图片描述

3）、访问路径
localhost:8080/webjars/jquery/3.4.1/jquery.js

三、自己的静态资源文件

1）、/**访问当前项目下的任何资源，(resources文件夹下的路径)

{
           "classpath:/META-INF/resources/",
           "classpath:/resources/",
           "classpath:/static/",
           "classpath:/public/"
 }