5 使用Mapper的接口编写Mybatis项目

张创琦 2022.03.12

1. 编写TeamMapper

package com.kkb.mapper; 
import com.kkb.pojo.Team;
import java.util.List;
/**
* ClassName: TeamMapper
* Mapper接口
* @author wanglina
* @version 1.0
*/
public interface TeamMapper { 
    List<Team> queryAll();
    Team queryById(int teamId); 
    int add(Team team);
    int add2(Team team);
    int update(Team team); 
    int del(int teamId);
}

1. TeamMapper.xml 的配置

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace=“完全限定名，接口的完全限定名”-->
<mapper namespace="com.kkb.mapper.TeamMapper">
<!-- 在这里直接复制Team.xml的内容即可 -->
    <!-- 查询所有结果 -->
    <select id="queryAll" resultType="com.kkb.pojo.Team">
        select * from team;
    </select>
    <!-- 根据ID查询 -->
    <!-- parameterType="参数的类型"，目前只支持一个参数 -->
    <!-- #{id}表示参数 id-自定义, 只需要符合命名规范即可, 没有实际对应意义 -->
    <select id="queryById" parameterType="int" resultType="com.kkb.pojo.Team">
        select * from team where teamId=#{id} ;
    </select>
    <!-- 删除一个球队 -->
    <delete id="del">
        delete from team where teamId=#{id};
    </delete>
    <!-- 删除多个球队-测试ok -->
    <delete id="del2">
        delete from team where location=#{loc};
    </delete>
    <!-- 根据球队编号更新信息 -->
    <update id="update" parameterType="com.kkb.pojo.Team">
        update team set teamName=#{teamName}, location=#{location} where teamId=#{teamId}
    </update>
    <!-- 添加一个球队 -->
    <!-- parameterType="com.kkb.pojo.Team" 将对象作为参数.
    注意 `` 符号的输入
    #{值} 值必须是实体类中的属性名称，其实就是占位符 ?  -->
    <insert id="add" parameterType="com.kkb.pojo.Team">
        INSERT INTO `team` (`teamName`, `location`, `createTime`)
        VALUES (#{teamName}, #{location}, #{createTime})
    </insert>
    <insert id="add2" parameterType="com.kkb.pojo.Team">
        INSERT INTO `team` (`teamId`,`teamName`, `location`, `createTime`)
        VALUES (#{teamId}, #{teamName}, #{location}, #{createTime})
    </insert>
</mapper>

1. mybatis.xml 配置文件中注册映射文件

<!-- 注册映射文件 -->
    <mappers>
        <mapper resource="com/kkb/pojo/Team.xml"/>
        <mapper resource="com/kkb/mapper/TeamMapper.xml"></mapper>
    </mappers>

1. 编写测试类

getMapper 方法获取代理对象

package com.kkb.test;
import com.kkb.dao.TeamDao;
import com.kkb.dao.TeamDaoImpl;
import com.kkb.mapper.TeamMapper;
import com.kkb.pojo.Team;
import com.kkb.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.Date;
import java.util.List;
/**
 *ClassName: TeamDaoTest
 *TeamMapper的测试类
 *@author wanglina
 *@version 1.0
 */
public class TeamMapperTest {
    // 调试成功，但是注意add和add2函数的利用，因为主键唯一的原因
    // 乱码问题尚未解决
    private SqlSession sqlSession = MybatisUtil.getSqlSession();
    @Test
    public void test01(){
        TeamMapper teamDao = sqlSession.getMapper(TeamMapper.class);
        //添加
        Team team = new Team();
        team.setTeamId(1001);
        team.setTeamName("勇士");
        team.setLocation("金州");
        team.setCreateTime(new Date());
        int num = teamDao.add(team);
        sqlSession.commit(); // 必须提交才能让增删改生效
        System.out.println(num);
        //更新
        Team team1 = teamDao.queryById(1001);
        team1.setTeamName("lina的球队");
        num = teamDao.update(team1);
        sqlSession.commit();//必须提交才能让增删改生效
        System.out.println(num);
        //删除
        num = teamDao.del(1001);
        sqlSession.commit();//必须提交才能让增删改生效
        System.out.println(num);
        //查询所有
        List<Team> teams = teamDao.queryAll();
        teams.forEach(t-> System.out.println(t));
    }
}