I know it is a bit weak for resistance but it is the way I build him

For farming, I got Tiatmat, it's the best item to farm because it allow you to kill lot of minions at the same time and with the wriggle's lantern, splash damage apllies half the 500 damage vs minions in splash damage.

First I get cloth armor because I am more tank than dps to survive early game, I return base when i got enough money to bur Madred's razors, then I buy Ninja tabi and then finish my wriggler's lantern. after this I get Tiatmat for farming, health regen and mana regen. Frozen mallet is a key for Jarvan, it gives you health and damage, just as the next item just own, Trinity Force. To finish my build, I get Atma's Impaler, because Jarvan IV with my build has more than 3K HP, so it gives me more than 60 damage and also it gives me armor and crit. With this build, You will get more than 3k HP, more then 300 damage, more than 1 attack speed and more than 200 armor.

Always get Demacian Standard when you can exept when you can grow Ult because it raise your armor and your attack speed permanently. Altern the Standard with Golden Aegis because it makes you able to take lots of damage while slowing ennemies to have a good escape. Why I get Dragon Strike at the end? Simply because it is only good when your DPS, and in the early game I make Jarvan more tankish for more survive ability and it is a little hard to cast in line with your Demacian Standard quickly so it is not worth the try.

I get heal just for early game to keep me from recalling a lot. I also get cleanse just for escaping while doing my Golden Aegis in case of a gank.

Well, I just got defence because I want to survive, IMO it's the best way to build him.

Physical damage rune are not worth it with Jarvan IV and don't forget to get mana runes because he struggles a lot with mana in early game.