IOC控制反转

1.set注入

1. UserDao

   public interface UserDao {
       void getUser();
   }
   

2. UserDaoImpl实现类

   public class UserDaoImpl implements UserDao{
       @Override
       public void getUser() {
           System.out.println("调用默认方式获取用户");
       }
   }
   

   public class UserDaoMysqlImpl implements  UserDao{
       @Override
       public void getUser() {
           System.out.println("mysql实现方式");
       }
   }
   

   public class UserDaoOracleImmp implements UserDao{
       @Override
       public void getUser() {
           System.out.println("oracl实现方式");
       }
   }
   

3. UserService业务层

   public interface UserService {
       void getUser();
   }

4. UserServiceImpl实现类

public class UserServiceImpl implements UserService {
    private UserDao userDao;

    public void setUserDao(UserDao userDao){
        this.userDao=userDao;
    }

    @Override
    public void getUser() {
        userDao.getUser();
    }
}

5. Test类

public class Test {
    public static void main(String[] args) {
        UserServiceImpl userService = new UserServiceImpl();
        userService.setUserDao(new UserDaoOracleImmp());
        userService.getUser();
    }
}

• 不用再去管理对象的创建，降低系统耦合性，可以更加专注在业务的实现