I just built a non-automatic Enderman-catching tower, and I want to share it with you. (although not sure how safe it is, one of them took a wooden plank and went to it's ethernal dream with it, so player-placed blocks endangered)
The process is quite simple, go up at nigh, look around for some endermen, then wait till they come near and drown in that 'little spoon of water'.
Although it's a bit buggy at the bottom with that glass ledge, they stand on it, so I had to sneak to the edge of the tower, but that's really not a problem to fix.
'Who want's to do, will always find a solution. Who Doesn't want to do, will always find an excuse.'
'If you want to teach something, you shall be the liveing example of it.'