Spring Boot 自动包规则原理

https://www.bilibili.com/video/BV19K4y1L7MT/?p=13

引导加载的自动配置类

@SpringBootApplication

……
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
		@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {

@SpringBootConfiguration

@Configuration
public @interface SpringBootConfiguration {

@Configuration

代表当前是一个配置类，使用 @SpringBootApplication 的类也会是 Spring Boot 中的一个配置类

@ComponentScan

包扫描注解，指定扫描哪些包；

@EnableAutoConfiguration

……
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {
……

@AutoConfigurationPackage

@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(AutoConfigurationPackages.Registrar.class) //给容器中导入一个组件
public @interface AutoConfigurationPackage {

比较关键的是 @Import(AutoConfigurationPackages.Registrar.class) 中导入的 AutoConfigurationPackages.Registrar

AutoConfigurationPackages.java

……	
        static class Registrar implements ImportBeanDefinitionRegistrar, DeterminableImports {

		@Override
		public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
			register(registry, new PackageImport(metadata).getPackageName());
		}

		@Override
		public Set<Object> determineImports(AnnotationMetadata metadata) {
			return Collections.singleton(new PackageImport(metadata));
		}

	}
……