sample sinatra mongodb

app.rb

require 'bundler/setup'
require 'json'
Bundler.require(:default)

class Thing
  include Mongoid::Document
  field :x, type: Integer
  field :j, type: Integer
end

class MyApp < Sinatra::Base
  configure :development do
    register Sinatra::Reloader
  end

  configure do
    Mongoid.load!("mongoid.yml")
  end

  get '/things.json' do
    content_type :json
    all_things = Thing.all
    all_things.to_json
  end
end

config.ru

require 'bundler'
Bundler.require

require './app'
run MyApp

Gemfile

source :rubygems

gem 'sinatra', require: 'sinatra/base'
gem 'sinatra-reloader', require: 'sinatra/reloader'
gem 'mongoid'
gem 'bson_ext'
gem 'thin'

Gemfile.lock

GEM
  remote: http://rubygems.org/
  specs:
    activemodel (3.2.1)
      activesupport (= 3.2.1)
      builder (~> 3.0.0)
    activesupport (3.2.1)
      i18n (~> 0.6)
      multi_json (~> 1.0)
    backports (2.3.0)
    bson (1.5.2)
    bson_ext (1.5.2)
      bson (= 1.5.2)
    builder (3.0.0)
    daemons (1.1.6)
    eventmachine (0.12.10)
    i18n (0.6.0)
    mongo (1.5.2)
      bson (= 1.5.2)
    mongoid (2.4.3)
      activemodel (~> 3.1)
      mongo (~> 1.3)
      tzinfo (~> 0.3.22)
    multi_json (1.0.4)
    rack (1.4.1)
    rack-protection (1.2.0)
      rack
    rack-test (0.6.1)
      rack (>= 1.0)
    sinatra (1.3.2)
      rack (~> 1.3, >= 1.3.6)
      rack-protection (~> 1.2)
      tilt (~> 1.3, >= 1.3.3)
    sinatra-contrib (1.3.1)
      backports (>= 2.0)
      eventmachine
      rack-protection
      rack-test
      sinatra (~> 1.3.0)
      tilt (~> 1.3)
    sinatra-reloader (1.0)
      sinatra-contrib
    thin (1.3.1)
      daemons (>= 1.0.9)
      eventmachine (>= 0.12.6)
      rack (>= 1.0.0)
    tilt (1.3.3)
    tzinfo (0.3.31)

PLATFORMS
  ruby

DEPENDENCIES
  bson_ext
  mongoid
  sinatra
  sinatra-reloader
  thin

mongoid.yml

development:
  host: localhost
  database: mydb