Raven is a build system for Java based on Ruby (more specifically Rake and Gem). Raven 1.1 has been released with a nice new feature: direct installation of a dependency. So you can easily do:

raven install httpclient
raven install -g xstream xstream:1.2
raven install --all -g axis2

And of course Raven still does its job:

* Your jar files are wrapped in a Ruby Gem (a package).
* Your dependencies are declared in a Rakefile.
* Raven gives you a small library of Rake tasks that you can use to compile your java classes, build a jar file, build a war file, produce javadoc, wrap the jar you built in a Gem, ...