Do not use rvm (or install and run from JRuby). The google-appengine gem must install into your system MRI. The appengine-sdk gem includes a complete Java app server. We bootstrap Java from MRI, then your app runs inside a servlet container (with access to all the APIs) using the version of JRuby installed into each app.
We assumed Rails 2 would never work without rubygems, and we committed to gem bunlder for JRuby on App Engine, so we were waiting for Rails 3. Fortunately, Takeru Sasaki was able to patch the Rails 2.3.x calls to rubygems, and now we have it working. Rails 2.3.x currently spins up several seconds faster than Rails 3, and just a few seconds behind Sinatra.
See the TInyDS version also: gist.github.com/gists/269075
One meta-gem provides the development environment
sudo gem install google-appengine
Install some gems you'll need
sudo gem install rails -v "2.3.9" sudo gem install rails_dm_datastore sudo gem install activerecord-nulldb-adapter
Create a folder for your app
mkdir rails_app; cd rails_app
Download and run the setup script
curl -O http://appengine-jruby.googlecode.com/hg/demos/rails2/rails239_appengine.rb ruby rails239_appengine.rb
Start development server
Open local console
Publish to production
We disable rubygems in the development environment, and the generators from Rails 2 perform various Gem dependency checks that are too difficult to patch, so we run the generators from the MRI. We also use Josh Moore's rails_dm_datastore integration plugin.
Generate a restful controller and add it to config/routes.rb
./script/generate scaffold contact title:string summary:text \ birthday:date url:string address:string phone:string -f --skip-migration
Generate a model for DataMapper
./script/generate dd_model contact title:string summary:text \ birthday:date url:link address:postal_address phone:phone_number -f
You’ve created a RESTful controller, and a DataMapper model