// generate the signature
params.computeSignature(requestMethod, url);
// make the request
HttpTransport transport = new NetHttpTransport();
HttpRequestFactory f = transport.createRequestFactory(params);
HttpRequest request = f.buildGetRequest(url);
HttpHeaders headers = new HttpHeaders();
headers.set("X-Factual-Lib", DRIVER_HEADER_TAG);
request.headers = headers;