Divide people into separate lobbies

I have a game that runs a web backend. At the moment, anyone that connects is put into the same "lobby" and joins the same game. We would like to make it so that multiple lobbies and games can be running on our server at the same time. How do I take my entire game and wrap it in something that can create new instances of my game (factory pattern?)? Right now our best way of doing it is to set up another server when we want to start a new game. If it helps, we are using Java on our backend (not my choice).