i'm pretty much newbie in topic of spring boot and hibernate, I'm making first kind of a project, but I don't understand how to approach good design in controller in following case:

I want to display data from google's book api, along with dropdown list with couple of items in it, whenever user will reach main page.

The list should contain a couple of items from enum, that with combination of result from input will create further api calls.

My struggle is as I said, for now, I can use just a list with hardcoded values, but when it'll come to display rest call result, and fetching data from database, I probably shouldn't do it in single method, right? So how should approach it, so I can avoid ambigious mapping, but still have fetched data from database and data from rest call?