Java Edition:Chainmail Armor
Chainmail armor is a recontinued feature. Chainmail was first normally obtainable in 12w21a (1.3 snapshot) via villager trading. Later in 12w32a (1.4 snapshot) it could also spawn naturally on mobs.
Obtaining
Beta 1.6 Test Build 3 Debug Chests
In Beta 1.6 Test Build 3, 11 chests spawned containing every item in the game. In the 9th chest to the left, there would be a chainmail helmet, chestplate, leggings, and boots.
9th chest to the right in Beta 1.6 Test Build 3
Fire Crafting
Fire as an item could also be obtained in Beta 1.6 Test Build 3. There used to be a crafting recipe for chainmail armor using fire in the same shapes as other armor. This crafting recipe works until 14w25a (1.8 snapshot), which removes fire as an item.
Crafting a chain helmet
Crafting a chain chestplate
Crafting chain leggings
Crafting chain boots
B Creative
In the version 11w49a (1.1 Snapshot), pressing B would toggle the player between Survival and Creative mode. This allowed the player to access the Creative Inventory where the player could then grab chainmail armor.
Villager
From 12w21a (1.3 snapshot) to 1.7.10 blacksmith villagers sold chainmail armor for emeralds, in 14w02a (1.8 Snapshot armorer villagers sold chainmail Armor for emeralds, and from 19w13a (1.14 Snapshot) to 24w20a (present) armorer villagers will give chainmail armor to players with the Hero of the Village effect.