引用：MyBatis的删除、修改、插入操作！！！-CSDN博客的准备工作！！！（准备工作都一样只不过文件名称有所不同）

1.利用原始DAO开发，查询所有的信息。

UserDao：

package com.by.dao;import com.by.pojo.User;import java.util.List;public interface UserDao {List<User> findAll();}

UserMapper.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.by.dao.UserDao"><select id="findAll" resultType="com.by.pojo.User">select  * from user</select>
</mapper>

与Mapper开发有所不同的是，原始Dao开发需要有接口的实现类：

UserDaoImpl： 接口的实现类的写法你需要注意调用的方法以及传递的参数。（参数为全类名+方法名）

/** Copyright (c) 2020, 2023,  All rights reserved.**/
package com.by.dao;import com.by.pojo.User;
import org.apache.ibatis.session.SqlSession;import java.util.List;public class UserDaoImpl implements UserDao{private SqlSession sqlSession;public UserDaoImpl(SqlSession sqlSession) {this.sqlSession = sqlSession;}@Overridepublic List<User> findAll() {return sqlSession.selectList("com.by.dao.UserDao.findAll");}}

测试类：

/** Copyright (c) 2020, 2023,  All rights reserved.**/
package com.by;import com.by.dao.UserDao;
import com.by.dao.UserDaoImpl;
import com.by.pojo.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 org.junit.Test;import java.io.IOException;
import java.io.InputStream;
import java.util.List;/*** <p>Project: mybatis - MyBatisTest</p>* <p>Powered by scl On 2023-12-18 11:44:53</p>* <p>描述：<p>** @author 孙臣龙 [1846080280@qq.com]* @version 1.0* @since 17*/
public class MyBatisTest {@Testpublic void testFindAll() throws IOException {// 加载配置文件String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);// 创建sqlSessionFActorySqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 获得数据的绘画实例SqlSession sqlSession = sessionFactory.openSession();UserDao userDao = new UserDaoImpl(sqlSession);List<User> userList = userDao.findAll();for (User str : userList) {System.out.println(str);}inputStream.close();sqlSession.close();}}

2.根据id查询信息

UserDao：

package com.by.dao;import com.by.pojo.User;
import java.util.List;public interface UserDao {User getUserById(Integer id);
}

UserDao.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.by.dao.UserDao"><select id="getUserById" resultType="com.by.pojo.User">select *from user where id=#{id};</select>
</mapper>

UserDaoImpl： 接口的实现类的写法你需要注意调用的方法以及传递的参数。（参数为全类名+方法名）

/** Copyright (c) 2020, 2023,  All rights reserved.**/
package com.by.dao;import com.by.pojo.User;
import org.apache.ibatis.session.SqlSession;
import java.util.List;public class UserDaoImpl implements UserDao{private SqlSession sqlSession;public UserDaoImpl(SqlSession sqlSession) {this.sqlSession = sqlSession;}@Overridepublic User getUserById(Integer id) {return sqlSession.selectOne("com.by.dao.UserDao.getUserById",id);}
}

测试类：

/** Copyright (c) 2020, 2023,  All rights reserved.**/
package com.by;import com.by.dao.UserDao;
import com.by.dao.UserDaoImpl;
import com.by.pojo.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 org.junit.Test;import java.io.IOException;
import java.io.InputStream;
import java.util.List;public class MyBatisTest {@Testpublic void getUserById() throws IOException {// 加载配置文件String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);// 创建sqlSessionFActorySqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 获得数据的绘画实例SqlSession sqlSession = sessionFactory.openSession();UserDao userDao = new UserDaoImpl(sqlSession);User user = userDao.getUserById(42);System.out.println(user);inputStream.close();sqlSession.close();}}