1.SpringBootApplication注解包含EnableAutoConfiguration注解
2.EnableAutoConfiguration注解包含@Import({AutoConfigurationImportSelector.class}),引入了负责自动配置的AutoConfigurationImportSelector
3. springboot容器启动时会导入AutoConfigurationImportSelector
4.这个selector会读取META-INF/spring-factories文件的配置中的EnableAutoConfiguration
spring-factories的内容如:
5.根据conditional过滤EnableAutoConfiguration实现,排除无效的配置
6. 把剩余的配置加载到IOC容器中,完成自动配置