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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 for the Service Control service.\u003c/p\u003e\n"],["\u003cp\u003eThe most recent release candidate is version 2.37.0-rc, with the current stable version listed as 2.24.0.\u003c/p\u003e\n"],["\u003cp\u003eThe UnifiedCredentialsOption can be utilized to override the default Application Default Credentials, allowing explicit loading of service account key files.\u003c/p\u003e\n"],["\u003cp\u003eExamples are given of how to implement the service account key override in \u003ccode\u003eQuotaControllerClient\u003c/code\u003e, \u003ccode\u003eServiceControllerClient\u003c/code\u003e, and \u003ccode\u003eServiceControllerClient\u003c/code\u003e classes, demonstrating usage across different API versions.\u003c/p\u003e\n"],["\u003cp\u003eThe documentation provides links to the best practices for managing service account keys and additional information about the \u003ccode\u003eCredentials\u003c/code\u003e objects and Authentication Components.\u003c/p\u003e\n"]]],[],null,[]]
