记录用户登录记录

   public void saveActiveUsersInPlatform(Long uid, String os, String version, String ip) {
    if(uid == null || uid == 0)return;
    UsersDTO usersDTO = usersManager.getUser(uid);
    if (usersDTO == null) {
        return;
    }
    //在线记录 user_online_record,
    //通过用户在线状态，进而更新用户连续每天在线情况
    Date date = new Date();
    String today = DateFormatUtils.YYYY_MM_DD.date2Str(date);
    //昨天
    Date day = DateTimeUtils.addDay(date, -1);
    String yesterday = DateFormatUtils.YYYY_MM_DD.date2Str(day);
    Date seven = DateTimeUtils.addDay(date, -7);
    String sevenDay = DateFormatUtils.YYYY_MM_DD.date2Str(seven);

    String todayCacheKey = CacheKey.getCacheKey(CacheKey.USER_DAY_ONLINE_RECORD, today);
    String uidStr = uid.toString();
    //今天登录记录
    String onlineFlag = redisManager.hget(todayCacheKey, uidStr);
    //记录用户在线记录
    redisManager.hset(todayCacheKey, uidStr, "1");
    //7天前登录记录
    String sevenDayLogin = redisManager.hget(CacheKey.getCacheKey(CacheKey.USER_DAY_ONLINE_RECORD, sevenDay), uidStr);
    //昨天前登录记录
    String yesterdayLogin = redisManager.hget(CacheKey.getCacheKey(CacheKey.USER_DAY_ONLINE_RECORD, yesterday), uidStr);

    if (StringUtils.isNotEmpty(onlineFlag)) {
        NewUserListenCountDto countDto = listenCountDao.selectByUid(uid);
        if (countDto != null) {
            if(org.apache.commons.lang.StringUtils.isEmpty(yesterdayLogin)) {
                //更新用户为非连续登录
                listenCountDao.updateContinueFlagByUid(uid);
            } else {
                //在线天数加1
                listenCountDao.updateOnLineDayByUid(uid);
            }
        }
    } else{
        //今天没有在线记录
        UserOnlineRecordDto recordDto = new UserOnlineRecordDto();
        recordDto.setUid(uid);
        recordDto.setNewFlag(1);
        //7天前登录过 表示老用户
        if(StringUtils.isNotEmpty(sevenDayLogin)){
            recordDto.setNewFlag(2);
        }
        recordDto.setCreateTime(date);
        recordDto.setUpdateTime(date);
        recordDto.setOs(os);
        recordDto.setIp(ip);
        recordDto.setVersion(version);
        //记录入库
        recordDao.save(recordDto);
    }
    redisManager.expire(todayCacheKey, 7, TimeUnit.DAYS);
}

1 画出代码逻辑流程图
2 找出代码逻辑缺陷和代码缺陷；
3 设计一个更优方案当前存在的问题和预计后期维护成本；