springboot对静态资源的映射规则

在WebMvcAutoConfiguration类中

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties
//可以设置和静态资源有关的参数

        @Override
		public void addResourceHandlers(ResourceHandlerRegistry registry) {
			if (!this.resourceProperties.isAddMappings()) {
				logger.debug("Default resource handling disabled");
				return;
			}
			Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
			CacheControl cacheControl = this.resourceProperties.getCache()
					.getCachecontrol().toHttpCacheControl();
			if (!registry.hasMappingForPattern("/webjars/**")) {
				customizeResourceHandlerRegistration(registry
						.addResourceHandler("/webjars/**")
						.addResourceLocations("classpath:/META-INF/resources/webjars/")
						.setCachePeriod(getSeconds(cachePeriod))
						.setCacheControl(cacheControl));
			}
			String staticPathPattern = this.mvcProperties.getStaticPathPattern();
			if (!registry.hasMappingForPattern(staticPathPattern)) {
				customizeResourceHandlerRegistration(
						registry.addResourceHandler(staticPathPattern)
								.addResourceLocations(getResourceLocations(
										this.resourceProperties.getStaticLocations()))
								.setCachePeriod(getSeconds(cachePeriod))
								.setCacheControl(cacheControl));
			}
		}

1. 所有/webjars/**,都去classpath:/META-INF/resources/webjars/找资源
   webjars:以jar包方式引用的静态资源 https://www.webjars.org/

<dependency>
			<groupId>org.webjars</groupId>
			<artifactId>jquery</artifactId>
			<version>3.4.1</version>
		</dependency>

localhost:8080/webjars/jquery/3.3.1/jquery.js

2. “/**” 访问当前项目的任何资源（静态资源的文件夹）

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

localhost:8080/abc 去静态资源文件夹

3. 欢迎页面映射，静态资源文件夹下所有index.html ,被 "/**"映射

        @Bean
		public WelcomePageHandlerMapping welcomePageHandlerMapping(
				ApplicationContext applicationContext) {
			return new WelcomePageHandlerMapping(
					new TemplateAvailabilityProviders(applicationContext),
					applicationContext, getWelcomePage(),
					this.mvcProperties.getStaticPathPattern());
		}

4. 配置首页图标

        @Configuration
		@ConditionalOnProperty(value = "spring.mvc.favicon.enabled",
				matchIfMissing = true)
		public static class FaviconConfiguration implements ResourceLoaderAware {

			private final ResourceProperties resourceProperties;

			private ResourceLoader resourceLoader;

			public FaviconConfiguration(ResourceProperties resourceProperties) {
				this.resourceProperties = resourceProperties;
			}

			@Override
			public void setResourceLoader(ResourceLoader resourceLoader) {
				this.resourceLoader = resourceLoader;
			}

			@Bean
			public SimpleUrlHandlerMapping faviconHandlerMapping() {
				SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping();
				mapping.setOrder(Ordered.HIGHEST_PRECEDENCE + 1);
				mapping.setUrlMap(Collections.singletonMap("**/favicon.ico",
						faviconRequestHandler()));
				return mapping;
			}

			@Bean
			public ResourceHttpRequestHandler faviconRequestHandler() {
				ResourceHttpRequestHandler requestHandler = new ResourceHttpRequestHandler();
				requestHandler.setLocations(resolveFaviconLocations());
				return requestHandler;
			}

			private List<Resource> resolveFaviconLocations() {
				String[] staticLocations = getResourceLocations(
						this.resourceProperties.getStaticLocations());
				List<Resource> locations = new ArrayList<>(staticLocations.length + 1);
				Arrays.stream(staticLocations).map(this.resourceLoader::getResource)
						.forEach(locations::add);
				locations.add(new ClassPathResource("/"));
				return Collections.unmodifiableList(locations);
			}

		}

	}