There's not really an easy way to do it that doesn't involving adding dozens (or more) lines of code.
If you don't want to hard code each entity's spawn locations, you can take advantage of a Map with the Class as key and the value being an array of biome names; these can be read from a config file (so users can modify the config) or simply populated via a static array from each entity class.
Once you have that map, you can add all of your spawn information in a simple loop.
The "static array from each entity class" is about the closest I got, but it still seemed like there might be a better way. Thanks for the help.