根据对应规格更新规格对应数量，库存

/**
      * 减库存
      * @param json 商品规格id 和 数量 json [{"standardid":"79","count":"5"},{"standardid":"81","count":"3"},{"standardid":"82","count":"2"},{"standardid":"83","count":"2"}]
      **/
     @RequestMapping(value = "/UpdateReduceStocks.json", method = RequestMethod.GET)
     @ResponseBody
     public Integer UpdateReduceStocks(String json) {
         HashMap<String , Object> map = new HashMap<>();
         net.sf.json.JSONArray jsonArr = net.sf.json.JSONArray.fromObject(json);
         String standardid[] = new String[jsonArr.size()];
         String count[] = new String[jsonArr.size()];
         for (int i = 0; i < jsonArr.size(); i++) {
             standardid[i] = jsonArr.getJSONObject(i).getString("standardid");
             count[i] = jsonArr.getJSONObject(i).getString("count");
         }
         for (int i = 0; i < standardid.length; i++) {
             System.out.print("规格id  "+standardid[i]+" ");
             System.out.print("数量 "+count[i]);
             System.out.println();
             Integer result = groupGoodsService.UpdateReduceStocks(parseInt(standardid[i]), parseInt(count[i]));
         }

         return 1;
}

Service:

//减库存
Integer UpdateReduceStocks(Integer standardId,Integer count);

Mapper.xml

<!--减库存-->1,0表示按顺序插入，不然不能插入多个或者改配置
<update id="UpdateReduceStocks" parameterType="map">
   UPDATE standard set stock = stock-#{1} where standard_id = #{0}
</update>