springboot静态资源配置原理

springboot对静态资源的配置可参考WebMvcAutoConfiguration这个类，在spring-boot-autoconfigure.jar中

WebMvcAutoConfiguration

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@Configuration(proxyBeanMethods = false) @ConditionalOnWebApplication(type = Type.SERVLET) @ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class }) @ConditionalOnMissingBean(WebMvcConfigurationSupport.class) @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10) @AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,         ValidationAutoConfiguration.class }) public class WebMvcAutoConfiguration {<br>   ....<br>}

@Configuration(proxyBeanMethods = false)：告诉容器这是一个配置类，且不代理bean方法，每次调用都会创建，这样容器启动时无需检查容器中是否已经存在

@ConditionalOnWebApplication(type = Type.SERVLET)：判断当前webAplication的类型是否为servlet，如果是则继续执行

@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })：判断必须存在指定的类才执行

@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)：判断必须没有指定的类才执行

@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)：控制执行顺序
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
ValidationAutoConfiguration.class })：在加载配置的类之后再加载当前类

WebMvcAutoConfigurationAdapter

在WebMvcAutoConfiguration这个类中，存在一个WebMvcAutoConfigurationAdapter 静态内部类，用于配置静态资源规则的。

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// Defined as a nested config to ensure WebMvcConfigurer is not read when not     // on the classpath     @Configuration(proxyBeanMethods = false)     @Import(EnableWebMvcConfiguration.class)     @EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })     @Order(0)     public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {    ....   }

　这个静态内部类中有且只有一个带参构造方法：

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public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties, WebMvcProperties mvcProperties,                 ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider,                 ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider) {             this.resourceProperties = resourceProperties;             this.mvcProperties = mvcProperties;             this.beanFactory = beanFactory;             this.messageConvertersProvider = messageConvertersProvider;             this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();         }

　　只有一个带参构造方法时，入参会从容器中进行查找。其中的 resourceProperties和mvcProperties是通过注解@EnableConfigurationProperties导入的，其中的XXXProperties又是通过指定前缀和配置文件进行绑定的；

WebMvcProperties

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1 2	@ConfigurationProperties(prefix = "spring.mvc") public class WebMvcProperties {

ResourceProperties

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@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false) public class ResourceProperties {       private static final String[] CLASSPATH_RESOURCE_LOCATIONS = { "classpath:/META-INF/resources/",             "classpath:/resources/", "classpath:/static/", "classpath:/public/" };

addResourceHandlers

在这个WebMvcAutoConfigurationAdapter 静态内部类中存在一个addResourceHandlers方法，这个方法就是用于静态资源规则配置使用的；

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@Override public void addResourceHandlers(ResourceHandlerRegistry registry) {         //检查是否开启默认资源处理，默认是true,可以通过配置文件改为false,关闭所有的静态资源配置映射        if (!this.resourceProperties.isAddMappings()) {           logger.debug("Default resource handling disabled");           return;        }        //同时通过配置文件可以添加缓存时间，秒为单位        Duration cachePeriod = this.resourceProperties.getCache().getPeriod();        CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();        if (!registry.hasMappingForPattern("/webjars/**")) {                      //对于webjars的访问全部映射到类路径下的/META-INF/resources/webjars/           customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**")                 .addResourceLocations("classpath:/META-INF/resources/webjars/")                 .setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));        }                 //获取静态资源的路径，默认是/**        String staticPathPattern = this.mvcProperties.getStaticPathPattern();        if (!registry.hasMappingForPattern(staticPathPattern)) {                  //对于配置的静态资源路径都会去this.resourceProperties.getStaticLocations()进行查找           customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern)                 .addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations()))                 .setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));        } }

　　this.resourceProperties.getStaticLocations()：这个就对应到ResourceProperties类中的CLASSPATH_RESOURCE_LOCATIONS；

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1 2	private static final String[] CLASSPATH_RESOURCE_LOCATIONS = { "classpath:/META-INF/resources/",             "classpath:/resources/", "classpath:/static/", "classpath:/public/" };

　

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spring: #  mvc: #    static-path-pattern: /res/**     resources:     add-mappings: false   禁用所有静态资源规则

　　

欢迎页的处理

欢迎页使用的welcomePageHandlerMapping方法

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@Bean<em id="__mceDel">public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext,<br>      FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {<br>   WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(<br>         new TemplateAvailabilityProviders(applicationContext), applicationContext, getWelcomePage(),<br>         this.mvcProperties.getStaticPathPattern());<br>   welcomePageHandlerMapping.setInterceptors(getInterceptors(mvcConversionService, mvcResourceUrlProvider));<br>   welcomePageHandlerMapping.setCorsConfigurations(getCorsConfigurations());<br>   return welcomePageHandlerMapping;<br>}</em><br>

　　HandlerMapping：处理器映射。保存了每一个Handler能处理哪些请求。

对于这个有参构造方法：

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WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders,             ApplicationContext applicationContext, Optional<Resource> welcomePage, String staticPathPattern) {         if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) {             logger.info("Adding welcome page: " + welcomePage.get());             setRootViewName("forward:index.html");         }         else if (welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {             logger.info("Adding welcome page template: index");             setRootViewName("index");         }     }

　　可以看出判断条件，如果开启了欢迎页且静态路径必须匹配/**则会去index.html，要么是跳转到index的请求。

      至此可以看出springboot对静态资源的所有默认规则。