driver_manager.rb

# saved as config/initializers/driver_manager.rb
class Java::java.sql::DriverManager
  class << self
    alias_method :get_connection_without_oracle, :getConnection
    def getConnection(*args)
      get_connection_without_oracle(*args)
    rescue => e
      if args.length == 2 && args[0] =~ /oracle/
        Java::oracle.jdbc.OracleDriver.new.connect(*args)
      else
        raise e
      end
    end
  end
end

Thanks a lot for that gist. This code snippet helped me a lot to get oracle enhanced running correctly with torquebox.