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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 version 2.34.0 being the current page's focus, and several prior versions accessible, ranging down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries by default use Application Default Credentials for Google Cloud Services authentication, however this default can be changed.\u003c/p\u003e\n"],["\u003cp\u003eTo override the default credentials, a user can utilize the UnifiedCredentialsOption to supply the authentication, as shown in the provided service account key file example.\u003c/p\u003e\n"],["\u003cp\u003eFor information on how to generate \u003ca href=\"https://cloud.google.com/cpp/docs/reference/common/latest/classgoogle_1_1cloud_1_1Credentials.html\"\u003e\u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e\u003c/a\u003e objects, the user can consult the Authentication Components section.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices on managing service account keys, you should consult the guide linked in the content, which will give more depth on this particular topic.\u003c/p\u003e\n"]]],[],null,[]]
