Spring中的DI

Posted 2020-11-03 liyue-sqsf

1. DI的概念
　　* DI -- Dependency Injection，依赖注入，在Spring框架负责创建Bean对象时，动态的将依赖对象注入到Bean组件中！！

2. applicationContext.xml配置信息，如下：

1 <bean id="userDao" class="com.demo.service.UserDaoImpl"></bean>
2     
3 <bean id="userService" class="com.demo.service.UserServiceImpl">
4     <!-- 依赖注入 -->
5     <property name="userDao" ref="userDao"></property>
6 </bean>

3. 代码示例：

 1 UserServiceImpl:
 2 public class UserServiceImpl implements UserService {
 3     
 4     // 提供成员属性，提供set方法
 5     private UserDao userDao;
 6     public void setUserDao(UserDao userDao) {
 7         this.userDao = userDao;
 8     }
 9     
10     @Override
11     public void sayHello() {
12         userDao.sayHello();
13     }
14 
15 }
16 
17 UserDaoImpl:
18 public class UserDaoImpl implements UserDao {
19 
20     @Override
21     public void sayHello() {
22         System.out.println("Dao  Hello!");
23     }
24 
25 }
26 
27 Demo:
28 public class Demo2 {
29     
30     @Test
31     public void run() {
32         // 创建工厂，加载配置文件
33         ApplicationContext context = new ClassPathXmlApplicationContext("/config/spring-mvc.xml");
34         // 获取对象
35         UserService userService = (UserService) context.getBean("userService");
36         // 调用方法
37         userService.sayHello();
38     }
39 
40 }

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