vert.x

Vert.x is a framework which takes inspiration from event driven frameworks like node.js, combines it with a distributed event bus and sticks it all on the JVM - a runtime with real concurrency and unrivalled performance. Vert.x then exposes the API in JavaScript, CoffeeScript, Ruby, Python, Groovy and Java.

Some of the key highlights include:

Polyglot. Write your application components in JavaScript, CoffeeScript, Ruby, Python, Groovy or Java. It's up to you. Or mix and match several programming languages in a single application. (Scala and Clojure support is scheduled too).
No more worrying about concurrency. Vert.x allows you to write all your code as single threaded, freeing you from the hassle of multi-threaded programming, yet unlike other asynchronous framework it scales seamlessly over available cores without you having to fork.
Vert.x has a super simple, asynchronous programming model for writing truly scalable non-blocking applications.
Vert.x includes a distributed event bus that spans the client and server side so your applications components can communicate incredibly easily. The event bus even penetrates into in-browser JavaScript allowing you to create effortless so-called real-time web applications.
Vert.x provides real power and simplicity, without being simplistic. No more boilerplate or sprawling xml configuration files.

If you don't want the whole vert.x platform, vert.x can also be used as a lightweight library in your Java or Groovy applications

Please see the website for full documentation and information on vert.x

The Vert.x project has moved here https://github.com/vert-x/vert.x