关于自定义错误处理

在项目中很多情况希望能自定义处理某些异常情况，通常采用重写rescue_action方法。一般网上能看到的代码都是以下的形式：

  def rescue_action(exception)
    rescue_action_in_public(exception)
  end

  def rescue_action_in_public(exception)
    logger.error("rescue_action_in_public executed")
    case exception
      when ActiveRecord::RecordNotFound, ActionController::RoutingError,  
      ActionController::UnknownAction,ActionController::UnknownAction
      logger.error("404 displayed")
      render(:file  => "#{RAILS_ROOT}/public/404.rhtml",:layout=>'error',
      :status => "404 Not Found")
    else
      logger.error("500 displayed")
      render(:file  => "#{RAILS_ROOT}/public/500.rhtml",:layout=>'error',
      :status => "500 Error")
    end
  end  

这样经常会报：
uninitialized constant ActionWebService::Dispatcher::ActionController::RoutingError错误，解决的办法是在ActionController前加::， 正确的格式应该如下：

    case exception
      when ActiveRecord::RecordNotFound, ::ActionController::RoutingError,  
      ::ActionController::UnknownAction,::ActionController::UnknownAction
      logger.error("404 displayed")
      render(:file  => "#{RAILS_ROOT}/public/404.rhtml",:layout=>'error',
      :status => "404 Not Found")
    else
      logger.error("500 displayed")
      render(:file  => "#{RAILS_ROOT}/public/500.rhtml",:layout=>'error',
      :status => "500 Error")
    end