Question

I am using Kaminari to handle pagination. I recently found out that a lot of bogus request is requesting an invalid page number, such as /post/page/undefined. Since I am using Solr, bad page number got passed into it and cause 500 error.

I want to be able to validate the page number, before it gets passed to the controller. So invalid page number will cause routing error instead.

I have asked the creator of Kaminari, and he gave a temporary solution. However I am wondering if there are cleaner ways to do this. I also don’t want to include this logic in every paginable resource, as that will be not DRY at all.

My route example:

resources :transactions do
  get 'page/:page', :action => :index, :on => :collection
end

Answer 1

I think a good solution is to simply remove or correct any invalid or frivolous page parameters and redirect to the corrected URL, like so:

# This goes in your relevant controller(s)
before_filter :correct_page_parameters!

# This goes in your application controller
def correct_page_parameters!
  supplied_parameters = params[:page]
  if supplied_parameters        
    proper_parameters = supplied_parameters.to_i

    if proper_parameters < 2
      params.delete(:page)
      redirect_to params
    elsif supplied_parameters != proper_parameters.to_s
      redirect_to params.merge(:only_path => true, :page => proper_parameters)
    end
  end
end

Hope this helps, good luck!