看下@SpringBootApplication的定义
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Configuration public @interface SpringBootConfiguration { } @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 { }可以看到@SpringBootApplication在功能上也是一个@Configuration。
这样就解释了，一般在SpringBoot的启动类上写了那么多注解，为啥可以被执行。