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::accesscontextmanager_v1::AccessContextManagerClient(
google::cloud::accesscontextmanager_v1::
MakeAccessContextManagerConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version available is 2.37.0-rc, with a variety of previous versions also accessible, all the way down to version 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries primarily use Application Default Credentials for Google Cloud Services authentication, but users can override this setting.\u003c/p\u003e\n"],["\u003cp\u003eYou can provide the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to override default credentials, as demonstrated in the example that showcases loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe example provided is intended to be simple and easy to follow, and it's recommended to refer to the best practices guide for managing service account keys for more information.\u003c/p\u003e\n"],["\u003cp\u003eFor details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, you can consult the Authentication Components documentation.\u003c/p\u003e\n"]]],[],null,[]]
