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.
In order to measure the total travel time you need custom code on the client side to emulate a browser or a specialized browser plugin.
You could use the standard Java library classes in the java.net and java.io packages and the System.currentTimeMillis() method to time a single request/response cycle. If you just want to measure the time in the servlet, ignoring network time, use currentTimeMillis in your doGet etc method.