基于MyBatis实现Dao编程

Posted 2020-10-24 sinceForever

基于MyBatis实现Dao编程

1、建立mybatis-config.xml文件

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"   "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration>    <!-- 配置全局属性 -->    <settings>       <!-- 使用jdbc的getGeneratedKeys获取数据库自增主键值 -->       <setting name="useGeneratedKeys" value="true" />       <!-- 使用列别名替换列名 默认:true -->       <setting name="useColumnLabel" value="true" />       <!-- 开启驼峰命名转换:Table{create_time} -> Entity{createTime} -->       <setting name="mapUnderscoreToCamelCase" value="true" />    </settings> </configuration>

 

2、在resources下创建mapper包放映射文件SecKillDao.xml和SuccessKilledDao.xml

SecKillDao.xml

<?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"> <mapper namespace="org.secKill.dao.SecKillDao">    <!-- 目的：为dao接口方法提供sql语句配置 -->    <update id="reduceNumber">       <!-- 具体的sql -->       UPDATE seckill       SET number = number - 1       WHERE          seckill_id = #{secKillId}       AND start_time <![CDATA[ <= ]]> #{killTime}       AND end_time >= #{killTime}       AND number > 0    </update>        <select id="queryById" resultType="SecKill" parameterType="long">       SELECT          seckill_id,          NAME,          number,          start_time,          end_time,          create_time       FROM          seckill       WHERE          seckill_id = #{secKillId}    </select>        <select id="queryAll" resultType="SecKill">       SELECT          seckill_id,          NAME,          number,          start_time,          end_time,          create_time       FROM          seckill       ORDER BY          create_time DESC       LIMIT #{offset},       #{limit}    </select>        <select id="killByProcedure" statementType="CALLABLE">       call execute_seckill (          #{secKillId, jdbcType = BIGINT, mode = IN },          #{phone, jdbcType = BIGINT, mode = IN },          #{killTime, jdbcType = TIMESTAMP, mode = IN },          #{result, jdbcType = INTEGER, mode = OUT }       )    </select> </mapper>

SuccessKilledDao.xml

<?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"> <mapper namespace="org.secKill.dao.SuccessKilledDao">    <insert id="insertSuccessKilled">       <!-- 主键冲突，报错 -->       INSERT ignore INTO success_killed (seckill_id, user_phone, state)       VALUES (#{secKillId}, #{userPhone}, 0)    </insert>        <select id="queryByIdWithSeckill" resultType="SuccessKilled">       <!-- 如何告诉MyBatis把结果映射到SuccessKilled同时映射seckill属性 -->       <!-- 可以自由控制SQL -->       SELECT          sk.seckill_id,          sk.user_phone,          sk.create_time,          sk.state,          s.seckill_id "seckill.seckill_id",          s.`name` "seckill.name",          s.number "seckill.number",          s.start_time "seckill.start_time",          s.end_time "seckill.end_time",          s.create_time "seckill.create_time"       FROM          success_killed sk       INNER JOIN seckill s ON sk.seckill_id = s.seckill_id       WHERE          sk.seckill_id = #{secKillId}       AND sk.user_phone = #{userPhone}    </select> </mapper>