Java同时处理多个请求

Question

I have an issue where user A submits a request, we call webservice and do some validations,pick record for that user from database and send back data.

Now, at the same time another user B submits a request, this time 2 records (user A,B records are picked from db).

My requirement is I want to pick only one record when user B submits the record. As per requirement, I cannot check against database for that particular record to pick only that one. This happens only when multiple people submit at same time.

We update a flag after sending response so that processed records are not picked up again when other request comes in.

The issue is, before this flag is updated if someone sends a request, then all records that has no flag is picked.

Can anyone suggest how can I design this in JAVA?

Answer 1

You should do some research on thread synchronisation.

Effectively you want one interaction (or at least part of it) to be completed before you perform the next. Of course, if the context of a web server, you don't want one interaction to block another. So there will be trade-offs.

One way would be to encapsulate the reading and flagging of the records in the database into a synchronised block, so that only one thread can execute that part of the interaction at a time.