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.
It is, but as of the that writing, and even as of today actually, the zero-configuration feature is under active development and will still see significant changes. For example, we plan to be bringing in the new Struts 2 Conventions Plugin into the main project, probably for Struts 2.1.3, and it is quite different than the current Struts 2 Codebehind Plugin.
Therefore, the book tends to favor the XML configuration, as it will work no matter the Struts 2 version.