依赖注入:DI
在使用Spring框架创建对象时,动态地将其所依赖的对象注入到Bean组件中,实现方式通常有两种:setter()方法注入;构造方法注入。前者更常用。
- 定义接口和实现类
public interface UserDao {
public void login();
}
public class UserDaoImpl implements UserDao {
@Override
public void login() {
System.out.println("UserDao login");
}
}
public interface UserService {
public void login();
}
public class UserServiceImpl implements UserService {
private UserDao userDao;
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
@Override
public void login() {
this.userDao.login();
System.out.println("UserService login");
}
}
- 配置xml文件
<bean id="userDao" class="dao.UserDaoImpl"/>
<bean id="userService" class="service.UserServiceImpl">
<property name="userDao" ref="userDao"/>
</bean>
- name表示相应的属性名,要set哪个属性
- ref用于指定其属性值,就是用哪个其他的bean来赋值
- 进行测试
public static void main(String[] args) {
ApplicationContext applicationContext =
new ClassPathXmlApplicationContext("spring.xml");
UserService userService = (UserService) applicationContext.getBean("userService");
userService.login();
}
输出: