This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
the Filter.init(FilterConfig) is called before any request is for the filter. This does NOT mean that the init method is called at the first request it receives. But it's not developer's concern the time when the init method is invoked.