params_parser.rb

# Custom error response of parse json
module MyApp
  class ParamsParser < ::ActionDispatch::ParamsParser
    def call(env)
      super
    rescue ::MultiJson::DecodeError
      [400, {'Content-Type' => 'application/json'}, [{message: 'JSON parse error'}.to_json]]
    end
  end
end

MyApp::Application.config.middleware.insert_before ActionDispatch::ParamsParser, MyApp::ParamsParser