public Result queryById(Long id) {
        // 1.从redis中查询店铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get("cache:shop:"+id);
        // 2.判断缓存是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return Result.ok(shop);
        }
        // 3.不存在，根据id查询数据库
        Shop shop = getById(id); // mybatisplus功能
        // 4.不存在，返回错误
        if (shop == null) {
            return Result.fail("店铺数据不存在");
        }
        // 存在，写入redis
        stringRedisTemplate.opsForValue().set("cache:shop:"+id, JSONUtil.toJsonStr(shop));
        return Result.ok(shop);
    }