Possible to... Mobs from spawners won't drop xp?

Hi, I made a plugin for my server to change how much xp mobs drop, but to prevent people from using xp grinders, is there a way to prevent mobs which were spawned from spawners to not drop xp? Thanks in advance, this is a big problem of mine considering that my server uses xp as its currency, thanks.

 

Use ExpirenceDropEvent

 

BajanAmerican Can you link me to the event? I can't seem to find it in the bukkit api docs, thanks.

Or if anyone has any ideas I would greatly appreciate it :3

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

I've seen someone asking this before, they did it this way:

Listen to CreatureSpawnEvent, then if it's equal to SpawnReason.SPAWNER (link)
Make a List/Array with the monster UUID, then listen to monster kill event.
If the killed mob his UUID is on the List/Array set .setDroppedExp to 0.

 

Alternatively, you could use entity metadata. That way you wouldn't have to keep a list anywhere and could simply check each mob for your metadata. Assign it when they spawn and check it when they die.