Springboot静态资源访问实现代码解析

//添加静态资源规则
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();
        //webjars依赖映射规则
        if (!registry.hasMappingForPattern("/webjars/**")) {
          this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{"/webjars/**"}).addResourceLocations(new String[]{"classpath:/META-INF/resources/webjars/"}).setCachePeriod(this.getSeconds(cachePeriod)).setCacheControl(cacheControl));
        }
				//本地配置的映射规则
        //this.resourceProperties.getStaticLocations() 从ResourceProperties中加载静态路径
        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));
        }

      }
    }

@ConfigurationProperties(
  prefix = "spring.resources",
  ignoreUnknownFields = false
)
public class ResourceProperties {
  //springboot默认的加载路径
  private static final String[] CLASSPATH_RESOURCE_LOCATIONS = new String[]{"classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/"};
  private String[] staticLocations;
  private boolean addMappings;
  private final ResourceProperties.Chain chain;
  private final ResourceProperties.Cache cache;

 <dependency>
      <groupId>org.webjars</groupId>
      <artifactId>jquery</artifactId>
      <version>3.3.1-2</version>
    </dependency>