@SpringBootApplication注解

@SpringBootApplication注解

由spring的源码可以知道

@SpringBootApplication注解包含了以下几个注解（均从SpringBootApplication.java中拷贝）

@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) })

且由标题上的原文注释可以得知

/**
* Indicates a {@link Configuration configuration} class that declares one or more
* {@link Bean @Bean} methods and also triggers {@link EnableAutoConfiguration
* auto-configuration} and {@link ComponentScan component scanning}. This is a convenience
* annotation that is equivalent to declaring {@code @Configuration},
* {@code @EnableAutoConfiguration} and {@code @ComponentScan}.
*
* @author Phillip Webb
* @author Stephane Nicoll
* @author Andy Wilkinson
* @since 1.2.0
*/

This is a convenience annotation that is equivalent to declaring {@code @Configuration}, {@code @EnableAutoConfiguration} and {@code @ComponentScan}.

该注解等同于@Configuration，@EnableAutoConfiguration，@ComponentScan这三个注解的组合。

@Configuration往往与@bean是同时使用的，这两个注解就可以构建一个简单的Spring的配置类，用来代替相应的xml文件，@Configuration表示能够使用Spring IOC（Inversion of Control/控制反转）容器作为bean的来源，bean注解就会告诉Spring，一个带有bean注解的方法返回一个对象。通常该对象被注册为Springcontext的bean。

@EnableAutoConfiguration是自动配置Spring的上下文。根据类路径和bean定义实现自动配置。

@ComponentScan会自动扫面有指定包下@Component的类并注册成为@bean，当然包括@Component下的子注解@Service,@Repository,@Controller

其下一般有一个 psvm方法，有个run方法，来引导。