On Tuesday, Google announced support for Java applications in App Engine. The new Java runtime environment provides the full Java 6 JVM (running with sandbox restrictions similar to the Python environment) and support for several important Java web application interface standards, including servlets, JavaServer Pages (JSPs), Java Data Objects (JDO) and the Java Persistence API (JPA), and other interface standards for the services. There's also a new Google Plugin for the Eclipse IDE with features for App Engine and Google Web Toolkit (GWT). You can develop GWT applications and run them on App Engine, using Java for both the server side and the client side. You can even write apps in languages other than Java that run in the JVM, such as JavaScript (using Rhino), Ruby (JRuby), Scala and Groovy.

I'm pleased to announce that Programming Google App Engine will cover the Java runtime environment. In general, the book will focus on concepts that apply to both languages and environments, with some sections dedicated to language-specific topics such as the data modeling interfaces. Java will get equal time with Python, though I'll probably use Python for examples that are illustrative of general concepts. There won't be enough room for a complete treatment of servlet-based applications and Java web tech, but thankfully there are several good books on those subjects already.

As a member of the team that worked on App Engine for Java, it's a pleasure and a relief to see it launched. I'm looking forward to returning my focus to the book, and adding Java to the mix. Finding the right organizational strategy for covering both languages in one book will be a challenge, so if you're a Rough Cuts subscriber, I'll be especially grateful for your feedback on the next few releases.