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::policysimulator_v1::SimulatorClient(
google::cloud::policysimulator_v1::MakeSimulatorConnection(options));
}
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis webpage provides documentation for the Policy Simulator, specifically focusing on versioned references and how to override authentication credentials, with the latest version being 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe content details how to override the default Application Default Credentials (ADC) used by client libraries for authenticating with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eOverriding credentials can be achieved by utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, and an example is provided demonstrating how to load a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe example provided showcases the usage of \u003ccode\u003egoogle::cloud::MakeServiceAccountCredentials\u003c/code\u003e and a minimal error handling to manage the service account credentials.\u003c/p\u003e\n"],["\u003cp\u003eFurther information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the Authentication Components section.\u003c/p\u003e\n"]]],[],null,[]]
