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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThis page provides documentation for the Access Context Manager C++ client library, with versions ranging from 2.11.0 to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe C++ client libraries use Application Default Credentials for authentication by default, but these can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eUsers can override the default authentication by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated in the example of loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices on managing service account keys, users should consult the linked guide, as the provided example is for demonstration purposes and may not be suitable for all environments.\u003c/p\u003e\n"],["\u003cp\u003eMore information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found under the linked "Authentication Components" section.\u003c/p\u003e\n"]]],[],null,[]]
