How to make an obsidian generator in minecraft?

While i don't really play minecraft, i do play mcpe and i would share with you how i farm obsidian
you will need a diamond pickaxe, a nether portal, iron ingots/buckets(or create an iron golem farm), and a water bucket. Btw iron golems and the farms for them are already out for 0.12.1

i collect the lava from the nether, bring it to the overworld, put them into a 1 block deep pit then allow water to run over them. According to my knowledge while i know that you can make an automatic lava creator with lava bucket, dispenser, hopper and some redstone circuits, it is impossible to push the obsidian with pistons, therefore it is hard to use the wither boss to break them

Gather Lava and Water into two separate buckets. Place these buckets in two holes which you have created but ensure that the water goes over the lava. So the hole which the lava is in is lower than the water, so the water falls on it. This way everytime they touch obsidian will be made

You can't anymore, the source block gets used every time an obsidian block is created. If water comes into contact with lava blocks that aren't the source, cobble will be created and if it contacts the source, the source will be converted into obsidian and can no longer be used.