Angry Villager      

Angry Villager, as you can see, have nothing different from normal Minecraft Villager. You can trade with them normally. Angry Villagers carry up to 4 items with them, but you have no way to knowing which items are. You will need to try... 

First, take off any item that you are holding and use your hands to hit the Angry Villager. Do this a lot of times. You will see items dropping from it. The number of hits that is needed is unknown, so you need to punch until it stops to drop things.

Be careful, when you hit the Angry Villager for the first time, it will start throwing arrows on you and it will call for help, so other near Angry Villagers will do the same at you.