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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 webpage provides documentation for the \u003ccode\u003eaccesscontextmanager\u003c/code\u003e C++ client library, covering versions from 2.11.0 up to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe client libraries primarily use Application Default Credentials for authentication, but users can override this by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eAn example is provided that demonstrates how to load a service account key file to override the default credentials.\u003c/p\u003e\n"],["\u003cp\u003eUsers are advised to consult the Best practices for managing service account keys guide for details on the key management process.\u003c/p\u003e\n"],["\u003cp\u003eThe Authentication Components section gives additional information on the creation of the \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
