7、Spring之基于注解管理bean

本质上：所有一切的操作都是Java代码来完成的，XML和注解只是告诉框架中的Java代码如何执行。

7.1、环境搭建

创建名为spring_ioc_annotation的新module，过程参考3.1节

7.1.1、创建spring配置文件

1. [/code][size=4]7.1.2、创建UserDao接口及实现类[/size]
3. [img]https://img2023.cnblogs.com/blog/2052479/202308/2052479-20230805183319834-573516107.png[/img]
4. [code]package org.rain.spring.dao;
6. /**
7. * @author liaojy
8. * @date 2023/8/5 - 18:32
9. */
10. public interface UserDao {
11. }

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1. package org.rain.spring.dao.impl;
3. import org.rain.spring.dao.UserDao;
5. /**
6. * @author liaojy
7. * @date 2023/8/5 - 18:33
8. */
9. public class UserDaoImpl implements UserDao {
10. }

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7.1.3、创建UserService接口及实现类

1. package org.rain.spring.service;
3. /**
4. * @author liaojy
5. * @date 2023/8/5 - 18:35
6. */
7. public interface UserService {
8. }

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1. package org.rain.spring.service.impl;
3. import org.rain.spring.service.UserService;
5. /**
6. * @author liaojy
7. * @date 2023/8/5 - 18:36
8. */
9. public class UserServiceImpl implements UserService {
10. }

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7.1.4、创建UserController

1. package org.rain.spring.controller;
3. /**
4. * @author liaojy
5. * @date 2023/8/5 - 18:38
6. */
7. public class UserController {
8. }

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7.2、注解和扫描

7.2.1、标识组件的常用注解

注解含义@Component将类标识为普通组件@Controller将类标识为控制层组件@Service将类标识为业务层组件@Repository将类标识为持久层组件

@Controller、@Service、@Repository这三个注解只是在@Component注解的基础上起了三个新的名字

从Spring使用IOC容器管理bean组件的角度来看，这四个组件注解没有区别

@Controller、@Service、@Repository这三个注解只是为了让开发人员便于分辨组件的作用

7.2.2、使用组件注解

7.2.2.1、@Controller注解

1. package org.rain.spring.controller;
3. import org.springframework.stereotype.Controller;
5. /**
6. * @author liaojy
7. * @date 2023/8/5 - 18:38
8. */
9. @Controller
10. public class UserController {
11. }

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7.2.2.2、@Service注解

注意：组件注解只能用于实现类，不能用于接口；因为bean的class属性只能是实现类，不能是接口

1. package org.rain.spring.service.impl;
3. import org.rain.spring.service.UserService;
4. import org.springframework.stereotype.Service;
6. /**
7. * @author liaojy
8. * @date 2023/8/5 - 18:36
9. */
10. @Service
11. public class UserServiceImpl implements UserService {
12. }

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7.2.2.3、@Repository注解

注意：组件注解只能用于实现类，不能用于接口；因为bean的class属性只能是实现类，不能是接口

1. package org.rain.spring.dao.impl;
3. import org.rain.spring.dao.UserDao;
4. import org.springframework.stereotype.Repository;
6. /**
7. * @author liaojy
8. * @date 2023/8/5 - 18:33
9. */
10. @Repository
11. public class UserDaoImpl implements UserDao {
12. }

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7.2.3、扫描组件注解

注意：为了减少扫描的耗时，推荐尽可能精确地指定package

1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4.        xmlns:context="http://www.springframework.org/schema/context"
5.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
7.    
8.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
9.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
10.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
12. </beans>

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7.2.4、测试

1. package org.rain.spring.test;
3. import org.junit.Test;
4. import org.rain.spring.controller.UserController;
5. import org.rain.spring.dao.UserDao;
6. import org.rain.spring.service.UserService;
7. import org.springframework.context.ApplicationContext;
8. import org.springframework.context.support.ClassPathXmlApplicationContext;
10. /**
11. * @author liaojy
12. * @date 2023/8/5 - 19:18
13. */
14. public class IOCByAnnotationTest {
16.     @Test
17.     public void testAutowireByAnnotation(){
19.         ApplicationContext ioc = new ClassPathXmlApplicationContext("spring-ioc-annotation.xml");
20.         UserController userController = ioc.getBean(UserController.class);
21.         System.out.println(userController);
22.         UserService userService = ioc.getBean(UserService.class);
23.         System.out.println(userService);
24.         UserDao userDao = ioc.getBean(UserDao.class);
25.         System.out.println(userDao);
27.     }
28. }

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7.3、高级扫描

7.3.1、排除扫描指定组件

7.3.1.1、方式一：根据注解指定排除(常用)

1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4.        xmlns:context="http://www.springframework.org/schema/context"
5.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
7.    
8.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
9.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
10.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
12. </beans><?xml version="1.0" encoding="UTF-8"?>
13. <beans xmlns="http://www.springframework.org/schema/beans"
14.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
15.        xmlns:context="http://www.springframework.org/schema/context"
16.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
18.    
19.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
20.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
21.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
23. </beans>   

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7.3.1.2、方式二：根据类型指定排除

1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4.        xmlns:context="http://www.springframework.org/schema/context"
5.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
7.    
8.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
9.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
10.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
12. </beans><?xml version="1.0" encoding="UTF-8"?>
13. <beans xmlns="http://www.springframework.org/schema/beans"
14.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
15.        xmlns:context="http://www.springframework.org/schema/context"
16.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
18.    
19.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
20.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
21.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
23. </beans>   

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7.3.2、仅扫描指定组件

7.3.2.1、方式一：根据注解指定包含(常用)

1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4.        xmlns:context="http://www.springframework.org/schema/context"
5.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
7.    
8.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
9.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
10.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
12. </beans><?xml version="1.0" encoding="UTF-8"?>
13. <beans xmlns="http://www.springframework.org/schema/beans"
14.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
15.        xmlns:context="http://www.springframework.org/schema/context"
16.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
18.    
19.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
20.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
21.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
23. </beans>            

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7.3.2.2、方式二：根据类型指定包含

1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4.        xmlns:context="http://www.springframework.org/schema/context"
5.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
7.    
8.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
9.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
10.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
12. </beans><?xml version="1.0" encoding="UTF-8"?>
13. <beans xmlns="http://www.springframework.org/schema/beans"
14.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
15.        xmlns:context="http://www.springframework.org/schema/context"
16.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
18.    
19.     <context:component-scan base-package="org.rain.spring.controller"></context:component-scan>
20.     <context:component-scan base-package="org.rain.spring.service"></context:component-scan>
21.     <context:component-scan base-package="org.rain.spring.dao"></context:component-scan>
23. </beans>            

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7.4、注解组件的id

7.4.1、默认情况

通过注解+扫描所配置的bean的id，默认值为类的小驼峰；即UserController类对应的bean的id就是userController

7.4.2、自定义

可通过标识组件的注解的value属性设置自定义的bean的id

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