SpringBoot 学习笔记 025 web场景-【源码分析】-静态资源原理

1. 静态资源配置原理

• SpringBoot 启动默认加载 xxxAutoConfiguration 类（自动配置类）
• SpringMVC 功能的自动配置类 WebMvcAutoConfiguration，根据 @Conditional 判断是否生效

@AutoConfiguration(
    after = {DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class, ValidationAutoConfiguration.class}
)
@ConditionalOnWebApplication(
    type = Type.SERVLET
)
@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class})
@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})
@AutoConfigureOrder(-2147483638)
public class WebMvcAutoConfiguration {

• 给容器中配了什么

    @Configuration(
        proxyBeanMethods = false
    )
    @Import({EnableWebMvcConfiguration.class})
    @EnableConfigurationProperties({WebMvcProperties.class, WebProperties.class})
    @Order(0)
    public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer, ServletContextAware {

• 配置文件的相关属性和 xxx 进行了绑定，根据 WebMvcProperties.class, WebProperties.class 查看

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

@ConfigurationProperties("spring.web")
public class WebProperties {

1.1 配置类只有一个有参构造器

• 有参构造器所有参数的值都会从容器中确定
• WebProperties 获取和 spring.web 绑定的值的所有的值的对象
• WebMvcProperties 获取和 spring.mvc 绑定的值的所有的值的对象
• ListableBeanFactory beanFactory Spring 的 beanFactory（即容器）
• ObjectProvider messageConvertersProvider 找到所有的 HttpMessageConverters
• ObjectProvider resourceHandlerRegistrationCustomizerProvider 找到资源处理器的自定义器
• ObjectProvider dispatcherServletPath
• ObjectProvider<ServletRegistrationBean<?>> servletRegistrations 给应用注册 Servlet、Filter等

        public WebMvcAutoConfigurationAdapter(WebProperties webProperties, WebMvcProperties mvcProperties, ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider, ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider, ObjectProvider<DispatcherServletPath> dispatcherServletPath, ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
            this.resourceProperties = webProperties.getResources();
            this.mvcProperties = mvcProperties;
            this.beanFactory = beanFactory;
            this.messageConvertersProvider = messageConvertersProvider;
            this.resourceHandlerRegistrationCustomizer = (ResourceHandlerRegistrationCustomizer)resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
            this.dispatcherServletPath = dispatcherServletPath;
            this.servletRegistrations = servletRegistrations;
            this.mvcProperties.checkConfiguration();
        }

1.2 资源处理的默认规则

        public void addResourceHandlers(ResourceHandlerRegistry registry) {
            if (!this.resourceProperties.isAddMappings()) {
                logger.debug("Default resource handling disabled");
            } else {
                // webjars 的规则
                this.addResourceHandler(registry, "/webjars/**", "classpath:/META-INF/resources/webjars/");
                this.addResourceHandler(registry, this.mvcProperties.getStaticPathPattern(), (registration) -> {
                    registration.addResourceLocations(this.resourceProperties.getStaticLocations());
                    if (this.servletContext != null) {
                        ServletContextResource resource = new ServletContextResource(this.servletContext, "/");
                        registration.addResourceLocations(new Resource[]{resource});
                    }

                });
            }
        }

1.2.1 禁用静态资源

spring:
  web:
    resources:
      add-mappings: false # 禁用所有静态资源规则

1.2.2 静态资源路径默认的4个位置

public static class Resources {
        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 boolean customized;
        private final Chain chain;
        private final Cache cache;

        public Resources() {
            this.staticLocations = CLASSPATH_RESOURCE_LOCATIONS;
            this.addMappings = true;
            this.customized = false;
            this.chain = new Chain();
            this.cache = new Cache();
        }

1.3 欢迎页的处理规则

handlerMapping：处理器映射，保存了每一个 handler 能处理哪些请求。

@Bean
        public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext, FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
            WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(new TemplateAvailabilityProviders(applicationContext), applicationContext, this.getWelcomePage(), this.mvcProperties.getStaticPathPattern());
            welcomePageHandlerMapping.setInterceptors(this.getInterceptors(mvcConversionService, mvcResourceUrlProvider));
            welcomePageHandlerMapping.setCorsConfigurations(this.getCorsConfigurations());
            return welcomePageHandlerMapping;
        }

    WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders, ApplicationContext applicationContext, Resource welcomePage, String staticPathPattern) {
        if (welcomePage != null && "/**".equals(staticPathPattern)) {
            // 要用欢迎页的功能，必须是 /**
            logger.info("Adding welcome page: " + welcomePage);
            this.setRootViewName("forward:index.html");
        } else if (this.welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {
            // 调用 Controller /index
            logger.info("Adding welcome page template: index");
            this.setRootViewName("index");
        }

    }