@SpringBootApplication

@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @SpringBootConfiguration @EnableAutoConfiguration @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), @Filter(type = FilterType.CUSTOM,     classes = AutoConfigurationExcludeFilter.class) }) public @interface SpringBootApplication { 

@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @AutoConfigurationPackage @Import(AutoConfigurationImportSelector.class) public @interface EnableAutoConfiguration {   String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration"; /**   * Exclude specific auto-configuration classes such that they will never be applied.   * @return the classes to exclude   */  Class<?>[] exclude() default {}; /**   * Exclude specific auto-configuration class names such that they will never be   * applied.   * @return the class names to exclude   * @since 1.3.0   */  String[] excludeName() default {}; } 

注意到AutoConfigurationImportSelector类

返回AutoConfigurationImportSelector.AutoConfigurationEntry基础上， AnnotationMetadata import的@Configuration类。

• autoConfigurationMetadata – 自动配置的元数据

• annotationMetadata – 配置类的注释元数据
  返回：应导入自动配置
  

• 获得配置
  返回应该被视为自动配置类名。 默认情况下，此方法将使用加载候选人SpringFactoriesLoader与getSpringFactoriesLoaderFactoryClass()

• 元数据 – 源元数据

• 属性-将annotation attributes
  返回：候选配置列表
  看下其中的断言中指定的

META-INF/spring.factories

为我们实现了很多自动装配

我们随便看下这个类

• 内嵌的 tomcat
  
• 其实就是开启 springMVC,这只是 sb 批量自动装配的一个组件
  

ServletWebServerFactoryAutoConfiguration

自动装配 – 启动一个内嵌的 tomcat