从用户到Spring MVC Controller方法的并发请求中的数据完整性

Question

I was hoping to understand how one can ensure data integrity in case of concurrent requests from same user to the same Spring Controller method ?

for egsuppose in an Online shopping scenario,a user happens to make concurrent requests to a Controller method (eg '/debitWallet?amount=100' to deduct his wallet money). The 'Wallet' could be a hibernate entity which is obtained in this method through a standard 'WalletService' instance -->'WalletDao' instance. Now how can we ensure data integrity of the wallet for concurrent requests?

• On what objects do I synchronize here?
• what would be the scope of different beans(service,dao etc.) although I don't see any way that would help since the Wallet is going to be taken from the data store?
• Should I even take the Wallet from the DB every-time the Controller method is invoked.Would it be a right approach? Instead should I use @SessionAttribute on this Wallet entity & then use it for every request to this method?

I could really use some help here to understand how to tackle data-integrity issue in this use case?

Answer 1

First of all answer the question: how frequent will be your data changed?

If it is not so frequent (or your database iterations are fast) you can use pattern: "User always operates with recent wallet instance, which is constantly synchronized with database". And to make it work user always sends Optimistick lock value (@Version field on entity), and in case changes happened in background: user receives Optimistick locking exception.

If it is frequent you should deeply analyze your implementation and then - search places for synchronization. Or even rework your API.