spring-boot 版本：2.4.3
- 不了解
DelegatingWebMvcConfiguration和WebMvcConfigurationSupport，先阅读这篇文章 EnableWebMvcConfiguration继承了DelegatingWebMvcConfiguration
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
}@EnableWebMvc就干了一件事导入DelegatingWebMvcConfiguration注册bean
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(WebProperties.class)
public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration implements ResourceLoaderAware {
...
}EnableWebMvcConfiguration继承了DelegatingWebMvcConfiguration并且DelegatingWebMvcConfiguration本身就是个配置类，所以也注册了bean
可以看出@EnableWebMvc和EnableWebMvcConfiguration做了同一件事情将DelegatingWebMvcConfiguration注册为bean,所以说EnableWebMvcConfiguration等效于@EnableWebMvc
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(WebProperties.class)
public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration implements ResourceLoaderAware {
/**
* 添加资源映射处理器
* @param registry
*/
@Override
protected void addResourceHandlers(ResourceHandlerRegistry registry) {
super.addResourceHandlers(registry);
//获取配置查看是否关闭了静态资源
if (!this.resourceProperties.isAddMappings()) {
logger.debug("Default resource handling disabled");
return;
}
ServletContext servletContext = getServletContext();
//webjars规则
addResourceHandler(registry, "/webjars/**", "classpath:/META-INF/resources/webjars/");
/**
* 项目配置的规则
* 1、配置项：spring.mcv.static-path-pattern 为访问前缀，默认值是 /**
* 2、配置项：spring.web.resource.static-locations 为静态资源目录，默认值是 {@code Resources#staticLocations}
*/
addResourceHandler(registry, this.mvcProperties.getStaticPathPattern(), (registration) -> {
registration.addResourceLocations(this.resourceProperties.getStaticLocations());
if (servletContext != null) {
/**
* 如果是servlet环境，那么servlet根目录也是资源目录
* 1、jar包运行时servlet根目录是随机的所以没啥用
* 2、war包运行时servlet根目录就是项目的根目录文件夹，如：\webapps\ROOT
* 综上所述 这个设置只有在war包运行时才有用
*/
registration.addResourceLocations(new ServletContextResource(servletContext, SERVLET_LOCATION));
}
});
}
private void addResourceHandler(ResourceHandlerRegistry registry, String pattern, String... locations) {
addResourceHandler(registry, pattern, (registration) -> registration.addResourceLocations(locations));
}
private void addResourceHandler(ResourceHandlerRegistry registry, String pattern,
Consumer<ResourceHandlerRegistration> customizer) {
if (registry.hasMappingForPattern(pattern)) {
return;
}
ResourceHandlerRegistration registration = registry.addResourceHandler(pattern);
customizer.accept(registration);
/**
* 浏览器缓存时间即cache-control响应头，spring.web.resources.cache配置项内进行配置
* 1、spring.web.resources.cache.period 设置客户端缓存时长(单位秒)
* 2、spring.web.resources.cache.cachecontrol 设置cache-control响应头更详细的信息
*/
registration.setCachePeriod(getSeconds(this.resourceProperties.getCache().getPeriod()));
registration.setCacheControl(this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl());
customizeResourceHandlerRegistration(registration);
}
...
}对浏览器缓存机制不太理解的可以查看这篇文章
WelcomePageHandlerMapping部分源码：
final class WelcomePageHandlerMapping extends AbstractUrlHandlerMapping {
...
WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders,
ApplicationContext applicationContext, Resource welcomePage, String staticPathPattern) {
//有index.html并且静态资源访问规则为/** 才生效index.html
if (welcomePage != null && "/**".equals(staticPathPattern)) {
logger.info("Adding welcome page: " + welcomePage);
setRootViewName("forward:index.html");
}
//存在index模板引擎，那么欢迎页就是他
else if (welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {
logger.info("Adding welcome page template: index");
setRootViewName("index");
}
}
...
}注意： 资源目录下有index.html，静态资源访问规则也必须为/**，具体原因看下图
当静态资源访问规则（static-path-pattern）复杂时可能就过滤掉了根目录的资源，所以根本无法访问根目录的index.html。
不过话说回来如果我只是添加一个前缀，完全可以进行识别，直接写死/**做的有点糙。但是话说回来现在大部分项目已经动静分离了，spring boot这个功能完全用不着。
EnableWebMvcConfiguration部分源码：
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(WebProperties.class)
public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration implements ResourceLoaderAware {
...
/**
* 欢迎页映射处理器
*/
@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext,
FormattingConversionService mvcConversionService,
ResourceUrlProvider mvcResourceUrlProvider) {
/**
* 创建欢迎页映射处理器
* getWelcomePage()是从静态资源目录获取index.html
* this.mvcProperties.getStaticPathPattern() 静态资源访问路径前缀
*/
WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(
new TemplateAvailabilityProviders(applicationContext), applicationContext, getWelcomePage(),
this.mvcProperties.getStaticPathPattern());
welcomePageHandlerMapping.setInterceptors(getInterceptors(mvcConversionService, mvcResourceUrlProvider));
welcomePageHandlerMapping.setCorsConfigurations(getCorsConfigurations());
return welcomePageHandlerMapping;
}
...
private Resource getWelcomePage() {
//遍历所有配置的资源目录，查找index.html
for (String location : this.resourceProperties.getStaticLocations()) {
Resource indexHtml = getIndexHtml(location);
if (indexHtml != null) {
return indexHtml;
}
}
ServletContext servletContext = getServletContext();
if (servletContext != null) {
//查找servlet根目录的index.html
return getIndexHtml(new ServletContextResource(servletContext, SERVLET_LOCATION));
}
return null;
}
private Resource getIndexHtml(String location) {
return getIndexHtml(this.resourceLoader.getResource(location));
}
//根据提供的资源获取index.html
private Resource getIndexHtml(Resource location) {
try {
Resource resource = location.createRelative("index.html");
if (resource.exists() && (resource.getURL() != null)) {
return resource;
}
}
catch (Exception ex) {
}
return null;
}
...
}WebMvcAutoConfiguration类上有个@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)注解也就是说用户自己使用了@EnableWebMvc那这个自动配置类全部失效。
@Configuration(proxyBeanMethods = false)
...
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
...
public class WebMvcAutoConfiguration {
...
}