@ComponentScan 的作用就是根据定义的扫描路径，把符合扫描规则的类装配到spring容器中，注解定义如下。

//
// Source code recreated from a .class file by IntelliJ IDEA
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//

package org.springframework.context.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.beans.factory.support.BeanNameGenerator;
import org.springframework.core.annotation.AliasFor;

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Repeatable(ComponentScans.class)
public @interface ComponentScan {
    @AliasFor("basePackages")
    String[] value() default {};

    @AliasFor("value")
    String[] basePackages() default {};

    Class<?>[] basePackageClasses() default {};

    Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;

    Class<? extends ScopeMetadataResolver> scopeResolver() default AnnotationScopeMetadataResolver.class;

    ScopedProxyMode scopedProxy() default ScopedProxyMode.DEFAULT;

    String resourcePattern() default "**/*.class";

    boolean useDefaultFilters() default true;

    ComponentScan.Filter[] includeFilters() default {};

    ComponentScan.Filter[] excludeFilters() default {};

    boolean lazyInit() default false;

    @Retention(RetentionPolicy.RUNTIME)
    @Target({})
    public @interface Filter {
        FilterType type() default FilterType.ANNOTATION;

        @AliasFor("classes")
        Class<?>[] value() default {};

        @AliasFor("value")
        Class<?>[] classes() default {};

        String[] pattern() default {};
    }
}

basePackages与value: 用于指定包的路径，进行扫描

basePackageClasses: 用于指定某个类的包的路径进行扫描

nameGenerator: bean的名称的生成器

useDefaultFilters: 是否开启对@Component，@Repository，@Service，@Controller的类进行检测

includeFilters: 包含的过滤条件

        FilterType.ANNOTATION：按照注解过滤

        FilterType.ASSIGNABLE_TYPE：按照给定的类型

        FilterType.ASPECTJ：使用ASPECTJ表达式

        FilterType.REGEX：正则

        FilterType.CUSTOM：自定义规则

excludeFilters: 排除的过滤条件，用法和includeFilters一样