玩转 Spring Boot 应用篇（解决菜菜店铺商品超卖问题）

<select id="getGoodsById" resultMap="BaseResultMap">
    select id, name, image, stock, price,start_time,end_time,create_time, update_time 
    from t_goods where id = #{id,jdbcType=INTEGER} for update 
</select>

变更前：
public int reduceStock(Integer goodsId,int quantity)
变更后：
public int reduceStock(Integer goodsId,int quantity,Integer version);

package org.growup.caicaishop.service;

import org.growup.caicaishop.entity.Goods;

import java.util.List;

public interface GoodsService {

    /**获取商品列表*/
    public List<Goods> findAllGoods();

    /**减库存*/
    public int reduceStock(Integer goodsId,int quantity,Integer version);
}

package org.growup.caicaishop.service.impl;

import org.growup.caicaishop.dao.GoodsDao;
import org.growup.caicaishop.entity.Goods;
import org.growup.caicaishop.service.GoodsService;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

@Service
public class GoodsServiceImpl implements GoodsService {

    @Resource
    private GoodsDao goodsDao;

    @Override
    public List<Goods> findAllGoods() {
        return goodsDao.selectAll();
    }

    @Override
    public int reduceStock(Integer goodsId,int quantity,Integer version) {
        return goodsDao.reduceStock(goodsId,quantity,version);
    }
}

package org.growup.caicaishop.dao;

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.growup.caicaishop.entity.Goods;

import java.util.List;

@Mapper
public interface GoodsDao {

    /**
     * 查询商品
     */
    public Goods getGoodsById(@Param("id")Integer id);

    /**
     * 查询所有商品
     */
    public List<Goods> selectAll();

    /**
     * 减库存
     */
    public int reduceStock(@Param("id")Integer id, @Param("quantity") int quantity,@Param("version") Integer version);
}

<?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.growup.caicaishop.dao.GoodsDao">

    <resultMap id="BaseResultMap" type="org.growup.caicaishop.entity.Goods">
        <id column="id" property="id" jdbcType="INTEGER"/>
        <result column="name" property="name" jdbcType="VARCHAR"/>
        <result column="image" property="image" jdbcType="VARCHAR"/>
        <result column="stock" property="stock" jdbcType="INTEGER"/>
        <result column="price" property="price" jdbcType="DECIMAL"/>
        <result column="version" property="version" jdbcType="INTEGER"/>
        <result column="start_time" property="startTime" jdbcType="TIMESTAMP"/>
        <result column="end_time" property="endTime" jdbcType="TIMESTAMP"/>
        <result column="create_time" property="createTime" jdbcType="TIMESTAMP"/>
        <result column="update_time" property="updateTime" jdbcType="TIMESTAMP"/>
    </resultMap>

    <select id="getGoodsById" resultMap="BaseResultMap">
        select id, name, image, stock, price,version,start_time,end_time,create_time, update_time
        from t_goods where id = #{id,jdbcType=INTEGER}
    </select>

    <select id="selectAll" resultMap="BaseResultMap">
        select id, name, image, stock, price,version,start_time,end_time,create_time, update_time from t_goods
    </select>

    <update id="reduceStock">
        update t_goods set stock = stock - #{quantity},version = version + 1 where id = #{id,jdbcType=INTEGER} and version = #{version,jdbcType=INTEGER}
    </update>
</mapper>

update t_goods set stock = stock - #{quantity},version = version + 1 where id = #{id,jdbcType=INTEGER} and version = #{version,jdbcType=INTEGER}

@Override
@Transactional(isolation = Isolation.READ_COMMITTED)
public boolean purchase(Integer userId, Integer goodsId, int quantity) {
    // 加入尝试固定次数限制
    for (int i = 0; i < 3; i++) {
        Goods goodsInfo = goodsDao.getGoodsById(goodsId);
        if (goodsInfo.getStock() < quantity) {
            // 库存不足
            logger.info("库存不足: " + goodsInfo.getStock());
            return false;
        }

        //扣减库存
        int res = goodsDao.reduceStock(goodsId, quantity, goodsInfo.getVersion());
        logger.info("扣减库存结果：" + res);
        if (res == 0) {
            logger.info("数据被修改，本次购买失败，继续尝试");
            continue;
        }
        //插入购买记录
        UserGoods userGoods = new UserGoods();
        userGoods.setUserId(userId);
        userGoods.setGoodsId(goodsId);
        userGoods.setQuantity(quantity);
        userGoods.setState(1);
        userGoods.setCreateTime(new Timestamp(System.currentTimeMillis()));
        int saveRes = userGoodsDao.insert(userGoods);
        logger.info("插入购买记录：" + saveRes);
        return saveRes == 1;
    }
    logger.info("重试 3 次后依然失败");
    return false;
}