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 is not required to call the next filter in the chain by invoking doFilter method on the filter chain.
If you don't want to invoke the next filter using chain.doFilter(request, response) you can just send the response back to the client and commit the response. You might want to do this if you are implementing a filter which checks for security, if you find that the request should not be forwarded to the actual target (may be a servlet) then you won't call doFilter and just send an HTTP error code back to the client (HTTP unauthorized error code 403).