- 组件扫描(component scanning): Spring 能够从 classpath 下自动扫描, 侦测和实例化具有特定注解的组件.
- @Component: 基本注解, 标识了一个受 Spring 管理的组件
- @Respository: 标识持久层组件
- @Service: 标识服务层(业务层)组件
- @Controller: 标识表现层组件
- 对于扫描到的组件, Spring 有默认的命名策略: 使用非限定类名, 第一个字母小写. 也可以在注解中通过 value 属性值标识组件的名称
- 当在组件类上使用了特定的注解之后, 还需要在 Spring 的配置文件中声明 <context:component-scan> :
- base-package 属性指定一个需要扫描的基类包,Spring 容器将会扫描这个基类包里及其子包中的所有类.
- 当需要扫描多个包时, 可以使用逗号分隔.
- 如果仅希望扫描特定的类而非基包下的所有类,可使用 resource-pattern 属性过滤特定的类,示例:
- <context:include-filter> 子节点表示要包含的目标类
- <context:exclude-filter> 子节点表示要排除在外的目标类
- <context:component-scan> 下可以拥有若干个 <context:include-filter> 和 <context:exclude-filter> 子节点
- <context:include-filter> 和 <context:exclude-filter> 子节点支持多种类型的过滤表达式:
package com.atguigu.spring.beans.annotation; import org.springframework.stereotype.Component; @Component public class TestObject { }
package com.atguigu.spring.beans.annotation.controller; import org.springframework.stereotype.Controller; @Controller public class UserController { public void execute() { System.out.println("UserController execute..."); } }
package com.atguigu.spring.beans.annotation.repository; public interface UserRepository { void save(); }
package com.atguigu.spring.beans.annotation.repository; import org.springframework.stereotype.Repository; @Repository("userRepository") public class UserRepositoryImpl implements UserRepository { @Override public void save() { System.out.println("UserRepository Save..."); } }
package com.atguigu.spring.beans.annotation.service; import org.springframework.stereotype.Service; @Service("userService") public class UserService { public void add() { System.out.println("UserService add..."); } }
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"> <!-- 指定Spring IOC 容器扫描的包 --> <!-- <context:component-scan base-package="com.atguigu.spring.beans.annotation"></context:component-scan> --> <!-- <context:component-scan base-package="com.atguigu.spring.beans.annotation" resource-pattern="repository/*.class"></context:component-scan>--> <!--<context:component-scan base-package="com.atguigu.spring.beans.annotation"> <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/> </context:component-scan>--> <!-- <context:component-scan base-package="com.atguigu.spring.beans.annotation" use-default-filters="false"> <context:include-filter type="annotation" expression="org.springframework.stereotype.Repository"/> </context:component-scan> --> <!-- <context:component-scan base-package="com.atguigu.spring.beans.annotation" > <context:exclude-filter type="assignable" expression="com.atguigu.spring.beans.annotation.repository.UserRepository"/> </context:component-scan> --> <context:component-scan base-package="com.atguigu.spring.beans.annotation" use-default-filters="false"> <context:include-filter type="assignable" expression="com.atguigu.spring.beans.annotation.repository.UserRepository"/> </context:component-scan> </beans>
package com.atguigu.spring.beans.annotation; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.atguigu.spring.beans.annotation.controller.UserController; import com.atguigu.spring.beans.annotation.repository.UserRepository; import com.atguigu.spring.beans.annotation.service.UserService; public class Main { public static void main(String[] args) { ApplicationContext apl = new ClassPathXmlApplicationContext("beans-annotation.xml"); // TestObject to = (TestObject) apl.getBean("testObject"); // System.out.println(to); // // UserController userController = (UserController) apl.getBean("userController"); // System.out.println(userController); // // UserService userService = (UserService) apl.getBean("userService"); // System.out.println(userService); UserRepository userRepository = (UserRepository) apl.getBean("userRepository"); System.out.println(userRepository); } }
结果:
六月 14, 2018 6:26:15 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh 信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@6193b845: startup date [Thu Jun 14 18:26:15 CST 2018]; root of context hierarchy 六月 14, 2018 6:26:16 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions 信息: Loading XML bean definitions from class path resource [beans-annotation.xml] com.atguigu.spring.beans.annotation.repository.UserRepositoryImpl@2f943d71