Python no longer is the only language supported by the Google App Engine. Google has today announced Java support on the Google App Engine. This could very well be the most important development to affect Java development in recent times.
With App Engine, you can build web applications using standard Java technologies and run them on Google’s scalable infrastructure. The Java environment provides a Java 6 JVM, a Java Servlets interface, and support for standard interfaces to the App Engine scalable datastore and services, such as JDO, JPA, JavaMail, and JCache.
Deploying Java web applications has always been a tough task as Java web applications were never shared hosting friendly and you had to buy an expensive dedicated server to get a Java web app to work properly, if at all.
To make things more exciting, it looks like you can not only deploy Java language apps but apps developed in all all languages that run on the JVM, like Groovy, Scala, JRuby, etc. However it has been noted that Grails applications aren’t working on the current version of Google App Engine as yet, so it does seem like there on limitations on the environment available on GAE.
The beta is currently open to only the first 10000, which should run out in a few hours. However you can very download the SDK and try things out locally. The included development server runs your application on your local computer for development and testing. The server simulates the App Engine datastore, services and sandbox restrictions. The development server can also generate configuration for datastore indexes based on the queries the app performs during testing.
More on the App Engine soon, after we try things out first hand.