Unless otherwise configured, the client libraries use Application Default Credentials to authenticate with Google Cloud Services. While this works for most applications, in some cases you may need to override this default. You can do so by providing the UnifiedCredentialsOption The following example shows how to explicitly load a service account key file:
[](std::string const& keyfile) {
auto is = std::ifstream(keyfile);
is.exceptions(std::ios::badbit); // Minimal error handling in examples
auto contents = std::string(std::istreambuf_iterator<char>(is.rdbuf()), {});
auto options =
google::cloud::Options{}.set<google::cloud::UnifiedCredentialsOption>(
google::cloud::MakeServiceAccountCredentials(contents));
return google::cloud::servicecontrol_v1::QuotaControllerClient(
google::cloud::servicecontrol_v1::MakeQuotaControllerConnection(
options));
}
Follow these links to find examples for other *Client classes:
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis page provides documentation for overriding default authentication credentials when using Google Cloud client libraries, specifically focusing on Service Control versions.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version available is 2.37.0-rc, and the content lists all the way back to version 2.11.0 with links to each.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries typically use Application Default Credentials, but the documentation details using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to override this with a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for \u003ccode\u003eservicecontrol_v1::QuotaControllerClient\u003c/code\u003e, \u003ccode\u003eservicecontrol_v1::ServiceControllerClient\u003c/code\u003e, and \u003ccode\u003eservicecontrol_v2::ServiceControllerClient\u003c/code\u003e to demonstrate credential override.\u003c/p\u003e\n"],["\u003cp\u003eThe page provides links to other relevant pages including the best practices for managing service account keys as well as authentication components for more information.\u003c/p\u003e\n"]]],[],null,[]]
