This build will give you a very tanky Jarvan that is still capable of dishing out quite a bit of damage throughout the entire game. ( Early Mid and Late )

Pros
-Easy last hitting due to his passive
-Excellent Lane Harrass with a E > Q > passive hit combo
-E>Q Combo will make you almost impossible to gank in the jungle
-Ulti will easily seperate a melee carry from his intended prey
-E>Q Combo can knock warwick's off their prey as well as knock up ( stun ) an entire team for 0.5 seconds
Cons
-Unable to jungle in the levels that matter ( 1-4 )

Armor penetration is an absolute must with Jarvan as all of his damage output is physical.

Attack Speed is helpful but these can be interchanged for AD runes just as easily.

Jarvan has a rather limited mana pool but you won't notice it with a few mp5 runes.

I play with Offensive masteries because I feel I don't deal as much damage as needed with Defensive runes nor do I need the extra defense. Jarvan is rarely focused and has no trouble going toe to toe with most champions in a 1v1, however, his playstyle does typically bring him to the middle of team fights and this is why I build him tankier than most do.

The build I have given you above is simply a core build.

If the opposing team has fed AP carries, I would recommend Force of Nature

If the opposing team has fed AD carries, I would recommend Thornmail or Frozen Heart

If you are not having any trouble surviving team fights then I would reccommend more damage.

Jarvan's main damage output is NOT auto attack. Having said this, straight AD / Arp / CDR outweighs stats like AS and crit. Once you are tanky enough it is time to stack bloodthirsters.

Jarvan is able to gank at level 2 if he has a competant lane partner. His Q>E>Auto attack passive combo will take someone down to around 50% or so at level 2 if they are a squishy. You'll want to land your E on top of your enemy and just behind him so that he takes damage from it and still gets knocked up when you Q in 0.5 seconds later.

I chose Ghost for chasing / running.

I chose Exhaust to incapacitate the enemy team's carries and mitigate the most damage possible they can put out on myself and my team's carries.