I'm trying to prevent the passive mobs (cows, etc.) from generating with the terrain, although I'll have them spawnable through other means later. I've run in a circle trying to figure this out. So far the only way I've found to do it is through this:

 

@SubscribeEvent
    public void onEntitySpawn(EntityJoinWorldEvent event){
        if (event.entity instanceof EntityChicken || event.entity instanceof EntityCow || event.entity instanceof EntitySheep || event.entity instanceof EntityPig || event.entity instanceof EntityRabbit || event.entity instanceof EntityWolf || event.entity instanceof EntityOcelot){
            event.setCanceled(true);
        }
    }

 

But that disables the creatures from ever spawning at all from any source. I have also tried the following, to no effect:

 

@SubscribeEvent
    public void spawnAnimals(LivingSpawnEvent.CheckSpawn event){
        if (event.entity instanceof EntityChicken || event.entity instanceof EntityCow || event.entity instanceof EntitySheep || event.entity instanceof EntityPig || event.entity instanceof EntityRabbit || event.entity instanceof EntityWolf || event.entity instanceof EntityOcelot){
            event.setCanceled(true);
            event.setResult(Event.Result.DENY);
        }
    }

    @SubscribeEvent
    public void genAnimals(PopulateChunkEvent.Populate event){
        if (event.type == PopulateChunkEvent.Populate.EventType.ANIMALS){
            event.setCanceled(true);
            event.setResult(Event.Result.DENY);
        }
    }

    @SubscribeEvent
    public void onEntitySpawn(EntityJoinWorldEvent event){
        if (event.entity instanceof EntityChicken || event.entity instanceof EntityCow || event.entity instanceof EntitySheep || event.entity instanceof EntityPig || event.entity instanceof EntityRabbit || event.entity instanceof EntityWolf || event.entity instanceof EntityOcelot){
            event.setResult(Event.Result.DENY);
        }
    }

 

So what is the proper way to do this? It looks to my research like I'd have to somehow change the spawn lists within the biome classes, and if I'm correct I have no idea how to do that. I hope I'm not correct.

I think it would be more "correct" to simply remove them from the natural spawning list.  I just use the EntityRegistry removeSpawn() method.

I think it would be more "correct" to simply remove them from the natural spawning list.

Except that also stops them from spawning naturally, later.

Which as I understood is exactly not what OP wants.

 

The OP said he wanted them to spawn later "through other means". I understood that to mean he would spawn them explicitly. Basically nothing auto-spawned. But you're right he might have meant something else.

My plan is to have the persistent mobs (cows, dogs, etc.) spawnable only by taming non-persistent mobs, or through creative/command methods. The only way I want them to not spawn is through terrain generation.

 

EDIT: Thank you Diesieben, that was the problem! The animals no longer spawn.