It's mostly just mentioned in the novels, if I'm not mistaken. It's served hot, steaming, in a cup much like a coffee cup. Plus, as columbob pointed out, it's just one letter away from 'java'.
I actually used it in my Lone Wolf game. The Shadaki Bucaneer had no other reason to come into port for the first session, so I made him a hired hand on a cargo ship that imported jala beans into Holmgard. It got the party together fairly well.