wubiqin/Spike

不加锁实现

    //read and check stock
    Stock stock = checkStock(sid);
    stockService.updateById(sid);
    return insertOrder(sid, stock);

会发生超卖

加乐观锁实现

不可重复读下读取不到其他事务提交到的数据，修改为read——committed

    Stock stock = checkStock(sid);

    updateStockOptimistic(sid, stock);

    return insertOrder(sid, stock);

redis加数据库乐观锁实现

    String countKey = RedisConstant.STOCK_COUNT + sid;
    String saleKey = RedisConstant.STOCK_SALE + sid;
    String versionKey = RedisConstant.STOCK_VERSION + sid;
    String nameKey = RedisConstant.STOCK_NAME + sid;
    if (redisTemplate.hasKey(countKey)) {
        logger.info("read stock from redis");
        return checkAndReadFromRedis(sid, countKey, saleKey, versionKey, nameKey);
    }
    //read from db and check stock
    Stock stock = checkStock(sid);
    updateStockOptimistic(sid, stock);
    //check insert order
    int result = checkInsertOrder(sid, stock);
    if (redisTemplate.hasKey(countKey)) {
        updateStockInRedis(countKey, saleKey, versionKey);
    }
    setKeyInRedis(countKey, saleKey, versionKey, nameKey, stock);
    return result;