Validating and saving a Gravatar URL

comment.rb

class AvatarValidator < ActiveModel::Validator
  def validate(record)
    unless gravatar_exists?
      return record.errors[:avatar] << "No display picture could be found on Gravatar using #{record.avatar}."
    end
  end
end

class Comment < ActiveRecord::Base
  has_one :post
  include ActiveModel::Validations
  validates_with AvatarValidator
  after_validation :save_avatar_link
end

private
  require "digest/md5"
  require "net/http"
  
  def gravatar_exists?
    hashed_email = Digest::MD5.hexdigest(self.avatar)
    gravatar_check = "http://gravatar.com/avatar/#{hashed_email}.png?d=404"
    uri = URI.parse(gravatar_check)
    http = Net::HTTP.new(uri.host, uri.port)
    request = Net::HTTP::Get.new(uri.request_uri)
    response = http.request(request)
    if (response.code.to_i == 404)
      return false
    else
      return true
    end
  end
  def save_avatar_link
    if gravatar_exists?
      hashed_email = Digest::MD5.hexdigest(self.avatar.downcase)
      self.avatar = "http://gravatar.com/avatar/#{hashed_email}.png"
    else
      self.avatar = "/assets/default_avatar.jpg"
    end
  end