I am investigating JMonkey and I notice that the early tutorials suggest placing game data in a hashmap on the geometry objects. Sure that is bad idea - reducing your entire data model to a bunch of hashmaps? Also, your game will be tightly bound to JMonkey - it would be really hard to swap in a new framework.
Am I missing something? Obviously the jmonkey approach keeps the class hierarchy flat - perhaps that has some performance benefit that I don’t understand.