传统开发方式

在Java目录下创建dao层接口类

package com.itheibai.dao;
import com.itheibai.entity.User;
import java.io.IOException;
import java.util.List;
public interface UserDao {
    public List<User> findAll() throws IOException;
}

在dao目录下创建,实现类

package com.itheibai.dao.impl;
import com.itheibai.dao.UserDao;
import com.itheibai.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class UserDaoImpl implements UserDao {
    @Override
    public List<User> findAll() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        List<User> userList = sqlSession.selectList("userMapper.findAll");
        return userList;
    }
}

创建service测试dao层

package com.itheibai.service;
import com.itheibai.dao.UserDao;
import com.itheibai.dao.impl.UserDaoImpl;
import com.itheibai.entity.User;
import java.io.IOException;
import java.util.List;
public class ServiceDemo {
    public static void main(String[] args) throws IOException {
        //创建dao层对象，这里dao层实现是手动编写的
        UserDao userDao = new UserDaoImpl();
        List<User> all = userDao.findAll();
        System.out.println(all);
    }
}

此时的目录结构