After Rails 4 Upgrade, one of our 3rd Party Integration Quickteller started failing.

No Transactions found post Rails4 Deploy when Reports Generated Later day

On inspecting further, we observed that Callback is failing at same point with message NoMethodError - undefined method '[]' for nil:NilClass: and had no Parmeters:

Twist in the tale is that service sends xml-encoded parameters and xml parameter parsing is removed from Rails 4 Core and needs to be included back to use the functionality :P

A XML parameters parser for Action Pack (removed from core in Rails 4.0)

• Include this gem into your Gemfile:
  • gem 'actionpack-xml_parser'
• Then, add ActionDispatch::XmlParamsParser middleware after ActionDispatch::ParamsParser in config/application.rb:
  • config.middleware.insert_after ActionDispatch::ParamsParser, ActionDispatch::XmlParamsParser
• You may need to require the ActionDispatch::XmlParamsParser manually. Add the following in your config/application.rb:
  • require 'action_dispatch/xml_params_parser'

Enjoy Rails 4 !!!