The following are the conditions that must be met before post form data will be populated to the parameter set:
1. The request is an HTTP or HTTPS request.
2. The HTTP method is POST.
3. The content type is application/x-www-form-urlencoded.
4. The servlet has made an initial call of any of the getParameter family of methods
on the request object.
If the conditions are not met and the post form data is not included in the
parameter set, the post data must still be available to the servlet via the request
object’s input stream. If the conditions are met, post form data will no longer be
available for reading directly from the request object’s input stream.
I did't understand the above paragraph at all. I wonder if there would be any condition to populate parameter set.