Quote from MazeCraft
A lever extends a piston (not visible) to stop new mobs from going into the cage. Then I push a button and another piston (also not visible) suffocate mobs. After that they are one-hit-kill. But I often use splash healing potions to kill them all at once and get xp. The regular piston visible on the picture is connected to a pressure plate on the floor. It pushes the drops towards me.
Then I retract the first piston and new mobs can go into the cage.
Sounds like it took a lot of work to set it up.My mob trap uses gravity but it lowers them down to about two hearts left so I just use splash potions to finish them off. I don't bother with hitting them because they spawn almost as fast as i can kill them with a sword.
Also I can't post any more today.