How to populate a drop down list

Hello community !

I've been searching on the forum how to populate a drop down list but I can only find cases where they populate a dialog drop down list.

I want to populate three drop down lists from a page. Which is the proper way of doing that ?

I would like to do something dynamical where I modify the next drop down list based on the selection from the first.

Can you point me to a guide which would help at least getting a drop down list populated from a servlet or something ?

Thank you !

PS: I'm using AEM 6.2