gistfile1.rb

# config.ru
require 'appengine-rack'
AppEngine::Rack.configure_app(
  :application => 'testapp',
  :version     => 2)
require 'testapp.rb'
run Sinatra::Application

# testapp.rb
require 'rubygems'
require 'sinatra'
require 'dm-core'

DataMapper.setup(:default, "appengine://auto")

class TestPersist
  include DataMapper::Resource

  property :id, Serial
  property :message, Text
end

get '/' do
  @t = TestPersist.all
  erb :index
end

post '/seed' do
  TestPersist.create(:message => params[:message])
  redirect '/'
end

# views/index.erb
<form method="post" action="/seed">
<textarea name="message"></textarea>
<input type="submit" value="Go">
</form>