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::apphub_v1::AppHubClient(
google::cloud::apphub_v1::MakeAppHubConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 document details how to override the default authentication credentials used by client libraries when interacting with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication uses Application Default Credentials, but specific credentials can be loaded using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e if necessary.\u003c/p\u003e\n"],["\u003cp\u003eAn example is provided showcasing how to explicitly load a service account key file to override authentication, which is relatively straightforward to understand.\u003c/p\u003e\n"],["\u003cp\u003eThe provided code snippet demonstrates setting authentication options using \u003ccode\u003egoogle::cloud::UnifiedCredentialsOption\u003c/code\u003e with a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eUsers are encouraged to consult the "Best practices for managing service account keys" guide for advanced credential management and the Authentication Components section for more info on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e.\u003c/p\u003e\n"]]],[],null,[]]
