基于MyBatis实现Dao编程

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>