Play Framework - getting data from an https form

Question

I've followed the tutorial for creating and validating an http form in Play:

http://www.playframework.com/documentation/2.2.x/JavaGuide4

But when I serve my login page through https instead of http, my email and password appear to me as null in the validate function. How would I validate the email and password if I'm using https- I can't use the null values.