Bean的依赖注入

1.创建 UserService，UserService 内部在调用 UserDao的save() 方法

package ioc1.it.dao;

public class userDaoImpl implements userDao {
    public userDaoImpl() {
        System.out.println("无参");
    }

    @Override
    public void save() {
        System.out.println("kachaq");
    }
}

 

public class UserServiceImpl implements UserService {
 public void save() {
 ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
 UserDao userDao = (UserDao) applicationContext.getBean("userDao");
userDao.save();
}
}

2.将 UserServiceImpl 的创建权交给 Spring

<bean id="userService" class="com.itheima.service.impl.UserServiceImpl"/>

3.从 Spring 容器中获得 UserService 进行操作

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
UserService userService = (UserService) applicationContext.getBean("userService");
userService.save();