Java、转账服务和并发问题

Question

我有这样的代码:

@Transactional(rollbackOn = RuntimeException.class)
    synchronized public void transfer(@NonNull final TransferModel transferModel) {
        log.info("Start processing money transfer from user: {} to receiver: {}. Transfer amount: {}", transferModel.getOwnerId(), transferModel
                .getReceiverId(), transferModel.getAmount());

        final AccountEntity ownerAccount = findByOwner(transferModel.getOwnerId());
        final AccountEntity receiverAccount = findByOwner(transferModel.getReceiverId());

        log.info("Owner balancer before transfer: {}. Receiver balance before transfer {}", ownerAccount.getBalance(), receiverAccount.getBalance());

        if (ownerAccount.getBalance().compareTo(transferModel.getAmount()) < 0) {
            throw new IllegalArgumentException("Owner has insufficient amount of money");
        }

        withdrawFromOwnerAccount(ownerAccount, transferModel.getAmount());
        depositToReceiverAccount(receiverAccount, transferModel.getAmount());

        log.info("Transfer money finished successful");
        log.info("Owner balancer after transfer: {}. Receiver balance after transfer {}", ownerAccount.getBalance(), receiverAccount.getBalance());
    }

简单的方法，从所有者那里收取金钱并传递给接收者。这个解决方案很幼稚，因为它一次不能处理多个传输。如何确保此方法能够处理多个请求并在并发环境中安全？

Answer 1

正如 GhostCat 提到的，我们不熟悉您的环境，因此如果任何“看起来天真”的方法有副作用，我们不会知道。

也就是说，假设这是一个非常简单明了的代码，并且方法名称反射(reflect)了它们正在做什么，我认为我们不必同步所有该方法，但只是关键部分:

withdrawFromOwnerAccount(ownerAccount, transferModel.getAmount());
depositToReceiverAccount(receiverAccount, transferModel.getAmount());

我们可以使用帐户同步这部分:

synchronized (ownerAccount) {
    withdrawFromOwnerAccount(ownerAccount, transferModel.getAmount());
}
synchronized (receiverAccount) {
    depositToReceiverAccount(receiverAccount, transferModel.getAmount());
}

通过这样做，我们能够并行执行此方法，并且仅当给予者/接收者已经在执行另一个事务时才锁定线程。

注意:为了应用此方法，您必须确保同一帐户没有两个对象!