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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 stable release is version 2.35.0, but version 2.37.0-rc is available as a release candidate, and several other versions are accessible, ranging down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries typically use Application Default Credentials for Google Cloud Services authentication, however this default can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eTo override default credentials, the UnifiedCredentialsOption can be used, as shown in the example using a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eLoading a service account key file is just one easy-to-understand method, and the Best practices guide should be consulted for more information on managing service account keys.\u003c/p\u003e\n"],["\u003cp\u003eAuthentication Components contain additional information on factory functions for creating Credentials objects.\u003c/p\u003e\n"]]],[],null,[]]
