Splitting jruby-complete.jar up for Google App Engine

When we write a web application using JRuby, we need jruby-complete.jar included in a war to use builtin libraries. The builtin libraries are supposed to be located under jruby.home, so the jruby.home system property is expected to be set correctly. However, we need an alternative to set the property since setting jruby.home on the web application doesn't make sense. The answer is jruby-complete.jar, which has builtin libraries under META-INF/jruby.home directory in it.

When we use Google App Engine, another problem pops up. GAE has 10MB limit per each file to upload (http://googleappengine.blogspot.com/2009/02/skys-almost-limit-high-cpu-is-no-more.html). The size of jruby-complete.jar is unfortunately over 10MB. The shell script to split jruby-complete.jar up into two jar archives has been introduced at http://olabini.com/blog/2009/04/jruby-on-rails-on-google-app-engine/. However, I learned the way in the blog was already obsolete when I filed JRUBY-3949. The smart way of doing that was already out there. The latest JRuby, I mean, JRuby 1.4.0dev in git HEAD has had a Rakefile to create jars.

This is what I acutually did on a terminal:

$ git clone git://kenai.com/jruby~main
$ cd jruby~main
$ export JRUBY_HOME=`pwd`
$ PATH=$JRUBY_HOME/bin:$PATH
$ ant
$ gem install rake
$ gem install hoe
$ cd gem
$ rake update

Then, jruby-core-1.4.0dev.jar and jruby-stdlib-1.4.0dev.jar was built in jruby~main/gem/lib directory.