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::apigateway_v1::ApiGatewayServiceClient(
google::cloud::apigateway_v1::MakeApiGatewayServiceConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 when using Google Cloud client libraries, specifically focusing on the \u003ccode\u003eApiGateway\u003c/code\u003e service.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version for the \u003ccode\u003eApiGateway\u003c/code\u003e service is 2.37.0-rc, with a historical list of versions down to 2.11.0 also being available.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication method utilizes Application Default Credentials, but can be overridden using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe provided code example demonstrates how to explicitly load a service account key file to override default credentials using the \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e function.\u003c/p\u003e\n"],["\u003cp\u003eFor further information, the page recommends consulting the "Best practices for managing service account keys" guide and provides a link to \u003ccode\u003eAuthentication Components\u003c/code\u003e documentation.\u003c/p\u003e\n"]]],[],null,[]]
