class GdsApi::JsonClient

def do_json_request(method, url, params = nil, additional_headers = {}, &create_response)

from the Net::HTTPResponse
create_response: optional block to instantiate a custom response object
additional_headers: headers to set on the request (in addition to the default ones)
params: the data to send (JSON-serialised) in the request body
url: the request URL
method: the symbolic name of the method to use, e.g. :get, :post 
def do_json_request(method, url, params = nil, additional_headers = {}, &create_response)
  begin
    if params
      additional_headers.merge!(self.class.json_body_headers)
    end
    response = do_request(method, url, (params.to_json if params), additional_headers)
  rescue RestClient::Exception => e
    # Attempt to parse the body as JSON if possible
    error_details = begin
      e.http_body ? JSON.parse(e.http_body) : nil
    rescue JSON::ParserError
      nil
    end
    raise build_specific_http_error(e, url, error_details)
  end
  # If no custom response is given, just instantiate Response
  create_response ||= proc { |r| Response.new(r) }
  create_response.call(response)
end