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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version available is 2.37.0-rc, with multiple previous versions available dating back to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eThe client libraries primarily use Application Default Credentials for Google Cloud Services authentication, which can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eYou can override default credentials by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, such as by loading a service account key file explicitly.\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 overriding authentication.\u003c/p\u003e\n"],["\u003cp\u003eThe best practice guide for managing service account keys is available and provides more information on this subject and authentication components can also be viewed for more context.\u003c/p\u003e\n"]]],[],null,[]]
