Spring @Autowird

dao层

@Repository
public class UserDaoImpl implements IUserDao{
    @Override
    public void add(User user) {
        System.out.println("dao 添加用户:" + user);
    }
}

service层

@Service
public class UserServiceImpl implements IUserService {
    @Autowired //spring会根据IUserDao类型自动寻找dao层的类型（他们都是bean了，和xml引用配置一个道理，当然可以使用@Qualifier指定id，前提是@Repository要有id）
    private IUserDao userDao;//注意类型是接口类型
    @Override
    public void add(User user) {
        System.out.println("service 添加用户:" + user);
        //调用dao
        userDao.add(user);
    }

controller层

@Controller
public class UserAction{
    @Autowired//spring自动注入userService赋值
    private IUserService userService;

    public void save(User user){
        System.out.println("保存用户 ");
        User user = new User("wang","123456");
        userService.add(user);
    }
}