spring-@Component/@ComponentScan注解

被@Component注解标注的注解有：@Service, @Repository, @Controller, @Configuration

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Indexed
public @interface Component {

    /**
     * The value may indicate a suggestion for a logical component name,
     * to be turned into a Spring bean in case of an autodetected component.
     * @return the suggested component name, if any (or empty String otherwise)
     */
    String value() default "";

}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Configuration {

    @AliasFor(annotation = Component.class)
    String value() default "";

}

@ComponentScan会扫描带有@Component注解的类
处理类：
ConfigurationClassParser
扫描类：

ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateComponentProvider 

protected void registerDefaultFilters() {
   this.includeFilters.add(new AnnotationTypeFilter(Component.class));

@ComponentScan:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Repeatable(ComponentScans.class) @since 1.8

public @interface ComponentScan {

一般的注解只能写一次，而被@Repeatable标注的注解可以写多次

@ComponentScan(basePackages = "com")
@ComponentScan(basePackages = "com.example")
public class Demo