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