前言
SpringBoot主启动类被@SpringBootApplication所修饰，点击进去该注解，出现上图，会发现其为组合注解，本章节将会基于注解进行解释其自动装配在源码层面是怎么实现的，完整的注解调用链路如下图所示：
@Inherited
@Target
@Documented
@Retention
AutoConfigurationExcludeFilter
TypeExcludeFilter
ComponentScan
@Configuration
SpringBootConfiguration
@Import(AutoConfigurationImportSelector.class)
@Import(AutoConfigurationPackages.Registrar.class)
@AutoConfigurationPackage
EnableAutoConfiguration
SpringBootApplication
