It only took a year (not bad) but now in addition to Python, Google App Engine now supports Java. This will be a huge boost to App Engine as it opens the service to a wider range of developer. I've played around with a few apps but I lacked the Python language knowledge to really create anything of substance.
I received my confirmation for the Java version yesterday and have just begun to poke around. Some of my favorite features include:
Eclipse Plugin for App Engine
- Create applications for both GWT and App Engine
- As-you-type code validation and syntax highlighting
- Run and debug (within Eclipse) applications locally
- App Engine deployment
- Support for JUnit (with datastore also!)
AppEngine Java SDK
- Support for Java 5 & 6 (Awesome!)
- Command line access to Google App Engine
- Dev web server to local testing. The server simulates the runtime functionaltiy of App Engine and all of its services including the datastore
- ANT scripts for common development tasks
- Implementations of JDO and JPI for access to the datastore (includes a query engine)
- Cron and Memcache support
- Authenticate user via Google Accounts
- Uploads via CSV to the datastore
I think my first application will be a simple Salesforce.com account browser. I'll see how easy it is to import the Enterprise WSDL and start developing.
Update: I just found out that the Java Early Look doesn't currently support web services ("We do not currently support JAX-RPC or JAX-WS.") Here's a list of what is and is not supported.