Temporary God

So, I would like to know how to temporarily "god" someone via the Bukkit API. So for a set amount of time when they log on for the first time, I'd like them to have godmode. By godmode, I mean they cannot hurt anyone or be hurt. I best understand with an example put in code, but I'll take any help I am given. Thanks!

BUMP.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.