JRuby and Rake

In my quest to write nothing but Ruby code in my copious free time, I’ve begun learning JRuby, which I’m finding an ideal solution to my Java projects, such as DiffJ and DoctorJ, which are dependent on Java because they use the parser from PMD.

Likewise I am migrating my build code away from Ant, using Gradle for the soon-to-be-released DiffJ 1.2.0. Thus I began trying to use the Ant library for Rake via JRuby, but was confounded by an error for the simple Rakefile:

require 'ant'

task :greet do
  puts "hello"
% jruby -S rake /usr/bin/rake:27:in `require': no such file to load -- rake (LoadError)
	from /usr/bin/rake:27

The fix was simple. Changing my mindset was more complicated: JRuby is looking for Ruby Gems in its own directory hierarchy, not the Ruby hierarchy.

So installing the Rake gem as follows fixed the problem:

% sudo jruby -S gem install rake