关于@SpringBootApplication注解一些自己的理解

@SpringBootApplication表示该类是主程序入口

我们点击该注解进去可以看到它其实是一个组合注解

@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

除去上面四个元注解外，我们主要关注下面三个注解。

继续往里看

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@documented
@Configuration
public @interface SpringBootConfiguration {
    @AliasFor(
        annotation = Configuration.class
    )
    boolean proxyBeanMethods() default true;
}

我们发现这个注解只是代表当前是一个配置类

往里看

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@documented
@Inherited
@AutoConfigurationPackage
@import({AutoConfigurationimportSelector.class})
public @interface EnableAutoConfiguration

依旧是一个组合注解

继续往里看

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@documented
@Inherited
@import({Registrar.class})
public @interface AutoConfigurationPackage

发现它通过@import注解给容器中添加了Registrar组件，继续查看这个组件

static class Registrar implements importBeanDefinitionRegistrar, Determinableimports {
        Registrar() {
        }

        public void registerBeanDefinitions(Annotationmetadata metadata, BeanDefinitionRegistry registry) {
            AutoConfigurationPackages.register(registry, (String[])(new AutoConfigurationPackages.Packageimports(metadata)).getPackageNames().toArray(new String[0]));
        }

        public Set