Spring ComponentScan注解详解

Spring中@ComponentScan注解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的bean容器中。

源码

@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 nameGenerator() default BeanNameGenerator.class;
 
    Class 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

注解方式

1. 扫描包

@ComponentScan(basePackages = “”)     //单个
@ComponentScan(basePackages = {“xxx”,“aaa”,“…”})   //多个

注意:可以省略“basePackages =”

@Configuration
@ComponentScan("com.51gjie.spring.service")
public class MyConfig {}

@Configuration
@ComponentScan("com.51gjie.spring.dao","com.51gjie.spring.service")
public class MyConfig {}

@Configuration
@ComponentScan("com.51gjie.spring.*")   //通配符匹配所有的包
public class MyConfig {}

2. 扫描类

@ComponentScan(basePackageClasses = “”)   //单个
@ComponentScan(basePackageClasses = {“aaa”,“bbb”,“…”})  //多个

注意:不可以省略“basePackageClasses =”

@Configuration
@ComponentScan(basePackageClasses = HelloController.class)
public class MyConfig {
}

总结

Spring ComponentScan注解有以下特性:

1. 自定扫描路径下边带有@Controller,@Service,@Repository,@Component注解加入spring容器

2. 通过includeFilters加入扫描路径下没有以上注解的类加入spring容器

3. 通过excludeFilters过滤出不用加入spring容器的类

4. 自定义增加了@Component注解的注解方式

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