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 DataMapper version also: gist.github.com/671792
One meta-gem provides the development environment
sudo gem install google-appengine
Install some gems you'll need
sudo gem install rails -v "2.3.10" sudo gem install rails_tiny_ds 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/rails2310_appengine.rb ruby rails239_appengine.rb tiny_ds
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 article title:string summary:text url:string \ pages:integer -f --skip-migration
Generate a model for TinyDS
./script/generate td_model article title:string summary:text url:string \ pages:integer -f
You've created a RESTful controller, and a TinyDS model