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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 webpage provides documentation for various versions of the C++ optimization library, ranging from version 2.11.0 up to the release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe content demonstrates how to override the default authentication credentials using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e by loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe example uses \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e to load the credentials from a provided service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe webpage also references the best practices guide for managing service account keys for more detailed security information.\u003c/p\u003e\n"],["\u003cp\u003eIt highlights the availability of additional information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects in the Authentication Components section.\u003c/p\u003e\n"]]],[],null,[]]
