After overcomplicating this thing several different ways, I see that I can simply set the experienceValue for the entity passed to my handler by the onLivingDeath event.

 

This works for hostile mobs. Now I just need to figure out why it isn't working for passive mobs.

 

EntityPig extends EntityAnimal extends EntityAgeable extends EntityCreature extends EntityLiving

EntityLiving is where the method onDeathUpdate() exists, which is the method that spawns the EntityXPOrb, so I'm guessing one of these other classes is overriding something.

Thank you. I can suppress all xp orbs easy enough within that event by checking that the name is "Experience Orb" and setting Event.setCanceled to true. The problem with this method is that I can't distinguish between a potion of enchanting, smelting xp, etc, and the mob dropped xp. Or at least I don't see a way. I was hoping there would be a way to see the source or dropping entity or something.

 

Thank you again, but I had tried that, and it has no effect. XP orbs still spawn.

You could try using LivingDeathEvent and setting EntityLiving.experienceValue to 0 for the dying entity.

 

This actually does work, but it has a "bug?" or something. I tried it this way first, but it didn't suppress the orbs. I was testing it on pigs. It turns out, this works fine on hostile mobs, but not on passive mobs.

 

It should work, as the EntityPig class extends the EntityAnimal class, which extends the EntityAgeable class, which extends the EntityCreature class, which extends the EntityLiving class, and EntityLiving class is where the method onDeathUpdate() exists, which is what spawns the EntityXPOrbs when mobs die.

 

I haven't looked at all of these classes to see if something is being overridden or anything though.

 

Just wanted to clarify that you were in fact correct.

 

Thank you again.