Does dracul's grasp cast a life tap on javazon?

Yes, throwing a javelin counts as "striking". These gloves are just poorly worded. Basically it means using any "attack" and not a "spell".

Source spells like Nova are NOT attacks, Assassin traps are NOT attacks, for example.

For your question with dracul's grasp cast a life tap on javazons, I included two examples to help with judging what is an attack and what is not.

Lightning strike and charged strike will proc because it hits with the javelin (the splits from lightning strike do not count because they count as a spell and not an attack), while a skill like poison javelin will NOT work, because it just leaves a trail of poison and doesn't hit. Open wounds also count towards this same rule.