Handling Parsing errors using Rack middleware in Rails 3.2

gistfile1.rb

#in application.rb
module YourApp
  class Application < Rails::Application
    config.middleware.insert_before ActionDispatch::ParamsParser, "ParsingFailureToJSON"
    ...
  end
end

#The Parsing failure middleware
class ParsingFailureToJSON
  def initialize app
    @app = app
  end

  def call env
    begin
      @app.call(env)
    rescue DecodeError #Obviously, this should be the error that you are interested in
      RailsFailureController.action(:parsing).call(env)
    end
  end
end

#RailsFailureController is a controller that can render anything using the full rails view layer.
#It makes rendering parsing errors using reusable error templates easy. You don't have to use a controller though