Devise authentication with multiple provider

authorization.rb

class Authorization < ActiveRecord::Base                                        
  attr_accessible :provider, :uid, :user_id                                     
                                                                                
  belongs_to :user, :inverse_of => :authorizations                                                                                                                                   
end

devise.rb

Devise.setup do |config|
  
  ...

   # These oauth key and secret are use for localhost. Please replace them if necessary
   config.omniauth :github, 'a55eb780a5a66bc2fabe', 'b531490bdcc4fcbb3e05bdca2e75e60b8ad9ba12'
   config.omniauth :facebook, "283956394958478", "fdfedf11fba5c4e77e87a748aad36cc9"
   config.omniauth :google_oauth2, '950211539633-6sh58gmv2mc39jn8m6b6uo9i5po6qkjh.apps.googleusercontent.com', 'pvDaViwlfKROcMTxhauo76Gu'
   #config.omniauth :twitter, "xfOsUPR6WPYzs3EXBbrag", "jxWQdnKr0KnzteXZHbVaE2JtbE6PzuKjOs9PnkeEag"
end

Gemfile

gem 'devise'

gem 'omniauth'
gem 'omniauth-github'
gem "omniauth-twitter"
gem "omniauth-facebook"
gem "omniauth-google-oauth2"

omniauth_callbacks.rb

# encoding: utf-8                                                                 
class User                                                                      
  module OmniauthCallbacks                                                      
    ["github","google_oauth2","twitter","facebook"].each do |provider|          
      define_method "find_or_create_for_#{provider}" do |response|              
        uid = response["uid"]                                                   
        data = response["info"]                                                 
                                                                                
        if user = Authorization.where("provider" => provider , "uid" => uid).first.try(:user)
          user                                                                  
        elsif user = User.find_by_email(data["email"])                          
          user.authorizations << Authorization.new(:provider => provider, :uid => uid )
          user                                                                  
        else                                                                    
          user = User.new(email: data["email"], username: data['nickname'] || data['name'])
                                                                                                                                                                                     
          if user.save(:validate => false)                                      
            user.authorizations << Authorization.new(:provider => provider, :uid => uid )
            return user                                                         
          else                                                                  
            Rails.logger.warn("User.create_from_hash 失败，#{user.errors.inspect}")
            return nil                                                          
          end                                                                   
        end                                                                     
      end                                                                       
    end                                                                         
  end                                                                           
end

omniauth_callbacks_controller.rb

# encoding: utf-8                                                               
class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController  
  def self.provides_callback_for(*providers)                                    
    providers.each do |provider|                                                                                                                                                     
      class_eval %Q{                                                            
        def #{provider}                                                         
          if not current_user.blank?                                            
            current_user.bind_service(env["omniauth.auth"])#Add an auth to existing
            redirect_to edit_user_registration_path, :notice => "成功绑定了 #{provider} 帐号。"
          else                                                                  
            @user = User.find_or_create_for_#{provider}(env["omniauth.auth"])   
                                                                                
            if @user.persisted?                                                 
              flash[:notice] = "Signed in with #{provider.to_s.titleize} successfully."
              sign_in_and_redirect @user, :event => :authentication, :notice => "登陆成功。"
            else                                                                
              redirect_to new_user_registration_url                             
            end                                                                 
          end                                                                   
        end                                                                     
      }                                                                         
    end                                                                         
  end                                                                           
                                                                                
  provides_callback_for :github, :twitter, :google_oauth2, :facebook            
                                                                                
  # This is solution for existing accout want bind Google login but current_user is always nil
  # https://github.com/intridea/omniauth/issues/185                             
  def handle_unverified_request                                                 
    true                                                                        
  end                                                                           
end 

registrations_controller.rb

class Users::RegistrationsController < Devise::RegistrationsController          
  def update                                                                    
    self.resource = resource_class.to_adapter.get!(send(:"current_#{resource_name}").to_key)
    prev_unconfirmed_email = resource.unconfirmed_email if resource.respond_to?(:unconfirmed_email)
                                                                                
    if resource.update_without_current_password(resource_params)                        
      if is_navigational_format?                                                
        flash_key = update_needs_confirmation?(resource, prev_unconfirmed_email) ?
          :update_needs_confirmation : :updated                                 
        set_flash_message :notice, flash_key                                    
      end                                                                       
      sign_in resource_name, resource, :bypass => true                          
      respond_with resource, :location => after_update_path_for(resource)          
    else                                                                        
      clean_up_passwords resource                                               
      respond_with resource                                                     
    end                                                                         
  end                                                                           
                                                                                
  protected                                                                     
                                                                                
  def update_needs_confirmation?(resource, previous)                            
    resource.respond_to?(:pending_reconfirmation?) &&                           
      resource.pending_reconfirmation? &&                                       
      previous != resource.unconfirmed_email                                    
  end                                                                           
end

routes.rb

devise_for :users, controllers: { omniauth_callbacks: "users/omniauth_callbacks" }

shell

rails g model Authorization provider:string user_id:integer uid:string
rake db:migrate

user.rb

class User < ActiveRecord::Base
  extend OmniauthCallbacks
  
  has_many :authorizations, :dependent => :destroy
  
  ...

  devise :database_authenticatable, :registerable,                              
         :recoverable, :rememberable, :trackable, :validatable, :omniauthable

  ...

  def bind_service(response)                                                    
    provider = response["provider"]                                             
    uid = response["uid"]                                                       
    authorizations.create(:provider => provider , :uid => uid )                 
  end

  def update_without_current_password(params, *options)                         
    params.delete(:current_password)                                            
                                                                                                                                                                                     
    if params[:password].blank?                                                 
      params.delete(:password)                                                  
      params.delete(:password_confirmation) if params[:password_confirmation].blank?
    end                                                                         
                                                                                
    result = update_attributes(params, *options)                                
                                                                                
    clean_up_passwords                                                          
    result                                                                      
  end 
end

XXXX_create_authorizations.rb

class CreateAuthorizations < ActiveRecord::Migration                                                                                                                                 
  def change                                                                    
    create_table :authorizations do |t|                                         
      t.string :provider                                                        
      t.integer :user_id                                                        
      t.string :uid                                                             
                                                                                
      t.timestamps                                                              
    end                                                                         
  end
end