A few months back speculations were high amongst the developer community about the fate of Java after the suspected takeover of Sun Microsystems by IBM, that was hot to be, and instead it was Oracle that was successful at it.Amidst speculations, came the announcement that G00gle has made Java available as the programming language for the Google App Engine. Since the launch of this App Engine, Google has only provided support to Python as a programming language, but Java had been the most requested feature for App Engine by the developer community. By moving beyond Python and embracing Java, Google has opel'led up avenues to develop Java based web applications that would run on Google's Cloud offering. Providing Java support to the Google App Engine also paves the way for other programming languages that run on Java virtual machines, for instance languages like JavaScript, Groovy or JRuby. In this article, we look at the App Engine Java overview and how you can develop and deploy an application on the Cloud.

Overview
The Google App Engine Java environment provides a Java 6 JVM, a Java Servlets interface, and also supports standard interfaces for data store and services like Java Data Objects, Java Per- sistence API, JavaMail, J cache, etc. The App Engine uses the Java Servlet standard for web applications, whereby the user or developer provides the application's servlet classes, JSP pages and other files along with the deployment descriptor in a standard WAR directory structure.



The applications are run in a secure 'sandbox' environment to isolate the application for service and security. This means that an application cannot spawn threads, or write data to local system files, thus ensuring that the application does not interfere with performance for other appllication on the cloud infrastructure.

Getting started
Since the applications on App Engine would run on Java 6 virtual machine, it is ideally required to use Java 6 for developing and testing the application. Though the App Engine SDK is compatible with Java 5 for development purpose, for developing apps for App Engine, you should have JDK 5 or JDK 6 installed on your system. And you can use Eclipse as a development environment. App Engine plug in is available for Eclipse versions 3.3 and 3.4, and through this plugin you can install the App Engine SDK from Eclipse using Software Updates. To do so, go to Help> Software updates and select the Available Software tab and there click on Add Site button. The available software list will get refreshed and a new entity appears named Google Update Site. Select this and its two options of SDKs and Plugins to install the Google App Engine SDK and integrate it with Eclipse. Now you can start developing apps for the Google's Cloud.