Cancelling CreatureSpawnEvent ?

Hi. I'm using the following code to cancel spawning of different mobs and spawn a zombie instead:

Code:java

 
    @SuppressWarnings("deprecation")
    @EventHandler
    public void onMonsterSpawn(CreatureSpawnEvent event) {
        if(event.getCreatureType() == CreatureType.SPIDER) {
            event.setCancelled(true);
            event.getEntity().getWorld().spawnEntity(event.getEntity().getLocation(), EntityType.ZOMBIE);        }
    }
 

This code generates a lot of server lag (probably a memory leak) and I'm unsure of how to fix the problem. Is there anywhere work around to do the same thing or to cover up the lag?

Thanks!

 

ThunderWaffeMC Doesnt seem to lag for me?

ThunderWaffeMC Maybe its the check time everytime a mob spawns because I dont have that

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

 

This is a classic issue with mob spawning - MC will constantly try to rebalance mobs, so this event fires like crazy if you keep canceling it.

The only way I know around this that seems to work well is moving the mob somewhere instead of canceling the event- but I don't know how plugins like MultiVerse and WorldGuard handle it, might be worth looking at their code!