How to prevent duplicate entries while refreshing?

Question

I have an index.jsp page where I have a form where the user enters some data that gets stored in the database using a Controller servlet.

I want to disp

Answer 1

I would add an invisible ID to the page. If the data is new to the database (ID = unknown), insert and create an ID and update the page with the ID. That way you know if it is a ID != unknown, and you don't have to do an insert. And if the data hasn't changed, you don't even have to do an update...