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::optimization_v1::FleetRoutingClient(
google::cloud::optimization_v1::MakeFleetRoutingConnection(options));
}
[[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 in the C++ client libraries for Google Cloud services.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available for optimization override authentication is 2.37.0-rc, with numerous other version options listed down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eBy default, the client libraries utilize Application Default Credentials (ADC) for authentication, but you can use the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to override this.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by explicitly loading a service account key file, as demonstrated in the provided C++ code example.\u003c/p\u003e\n"],["\u003cp\u003eFor a comprehensive understanding of creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, refer to the "Authentication Components" documentation.\u003c/p\u003e\n"]]],[],null,[]]
