Ruby on Railsのエラーハンドリング

errors_controller.rb

class ErrorsController < ActionController::Base
  NOT_FOUND      = 404
  STANDARD_ERROR = 500

  rescue_from StandardError, with: :error_500
  rescue_from AbstractController::ActionNotFound, with: :render_404
  rescue_from ActionController::RoutingError,     with: :render_404

  layout false

 def render_404(e)
   respond_to do |format|
     format.html { render file: "#{Rails.root}/public/404.html", status: NOT_FOUND }
     format.json { render json: { status: NOT_FOUND, result: e.try(:message) } }
   end
 end

 def render_500(e)
    logger.error "500 exception: #{e.try(:message)}"
    respond_to do |format|
      format.html { render file: "#{Rails.root}/public/500.html", status: STANDARD_ERROR }
      format.json { render json: { status: STANDARD_ERROR, result: e.try(:message) } }
    end
 end

 def thow; raise request.env["action_dispatch.exception"]; end
end

initializers.rb

Rails.application.configure do
  config.exceptions_app = ->(env) { ErrorsController.action(:thow).call(env) }
end