Question

I have a Servlet when a request comes it checks for the user id and then if id is not there it creates a new user id in the database. But if I get multiple requests with a very short delay then all those request tend to see that there is not user at the moment and create multiple users with the same name. I just don’t want to make the user id field unique to solve this problem. Other than the user id I store some related data as well.

I need to know how to keep a DB locked until one Servlet request is finished processing.

Answer 1

You need to make your servlet code synchronized.

Easy way is to make your servlet implement SingleThreadModel.

http://www.javatpoint.com/SingleThreadModel-interface

But this is not a good approach as your servlet will handle only one thread/request at a time. Good solution is to synchronize the part where you check and generate the uid.