Google App Engine Java and GWT Application Development by Amy Unruh

This is a practical guide with a step-by-step approach that builds an application in stages. Each stage of the application is used along with screenshots to introduce or develop your understanding of how to write powerful GAE applications. If you are a developer with prior programming experience of Java development and object-oriented programming and want to understand the key concepts of how to build AJAX web applications with Java, then this book is for you. The book assumes some previous exposure to the basics of using GWT, for example at the level of Googles online introductory GWT tutorials. You dont need to know anything about Google App Engine. This book will teach you everything you need.