AR_ERROR_CLASSES = [ActiveRecord::RecordNotFound, ActiveRecord::StatementInvalid] 
  ERROR_CLASSES = [NameError, NoMethodError, RuntimeError, 
         ActionView::TemplateError, 
         ActiveRecord::StaleObjectError, ActionController::RoutingError, 
         ActionController::UnknownController, AbstractController::ActionNotFound, 
         ActionController::MethodNotAllowed, ActionController::InvalidAuthenticityToken] 
 
  ACCESS_DENIED_CLASSES = [CanCan::AccessDenied] 
 
  if Rails.env.production? 
    rescue_from *AR_ERROR_CLASSES, :with => :render_ar_error 
    rescue_from *ERROR_CLASSES, :with => :render_error 
    rescue_from *ACCESS_DENIED_CLASSES, :with => :render_access_denied 
  end 
   
  #called by last route matching unmatched routes.  Raises RoutingError which will be rescued from in the same way as other exceptions. 
 
#備注rails3.1后ActionController::RoutingError在routes.rb中最后加如下代碼才能catch了。 
#rails3下：match '*unmatched_route', :to => 'application#raise_not_found!' 
#rails4下：get '*unmatched_route', :to => 'application#raise_not_found!' 
 
  def raise_not_found! 
    raise ActionController::RoutingError.new("No route matches #{params[:unmatched_route]}") 
  end 
 
  def render_ar_error(exception) 
    case exception 
    when *AR_ERROR_CLASSES then exception_class = exception.class.to_s 
    else exception_class = 'Exception' 
    end 
 
    send_error_email(exception, exception_class) 
  end 
 
  def render_error(exception) 
    case exception 
    when *ERROR_CLASSES then exception_class = exception.class.to_s 
    else exception_class = 'Exception' 
    end 
 
    send_error_email(exception, exception_class) 
  end 
 
  def render_access_denied(exception) 
    case exception 
    when *ACCESS_DENIED_CLASSES then exception_class = exception.class.to_s 
    else exception_class = "Exception" 
    end 
 
    send_error_email(exception, exception_class) 
  end