Alloy - Generate .xml instance from .als

I need to generate random .xml instances from an .als in my program. I managed to do that by running alloy in background (invisible JFrame) and calling the doOpen, doExecuteLatest and doShowLatest functions. But having to wait alloy to start every time I run my code is a pain. I think it would be more efficient if I simply used the alloy code section that does this procedure (I imagine that would be kodkod). Does anyone know how to do that? I found alloy's code to be pretty confusing...