Ruby CGI code on rails framework

I'm new to Ruby and Rails and am to develop and write a simple connector to use an API Service for my Rails APP. I have a connector which uses CGI class with RUby. Now I want to implement the same on rails platform. How will it go? What are the alternative classes (or gems) that provide similar functionality as of CGI for rails

As for instance I have this code :

cgi = CGI.new
if cgi.params['jsonString']!=""
    data=cgi.params['jsonString'].to_s
    data.delete! '\\'
    data.delete! '['
    data.delete! ']'
    data=data[1..-1]
    data=data[0..-2]
    shieldsquare_service_url = 'http://' + $_ss2_domain + '/getss2data'
    shieldsquare_request = JSON.parse(CGI::unescape(data))
    shieldsquare_request["sid"] = $_sid
    shieldsquare_request["host"] = ENV[$_ipaddress]
    shieldsquare_post_data = JSON.generate(shieldsquare_request)
    if $_async_http_post== true
        error_code=shieldsquare_post_async shieldsquare_service_url,               shieldsquare_post_data,$_timeout_value.to_s
    else
        error_code=shieldsquare_post_sync shieldsquare_service_url, shieldsquare_post_data, $_timeout_value
    end
end

Please Guide me on this topic