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::datastore_admin_v1::DatastoreAdminClient(
google::cloud::datastore_admin_v1::MakeDatastoreAdminConnection(
options));
}
Follow these links to find examples for other *Client classes:
[[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 overriding default authentication credentials when using Google Cloud C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version is 2.37.0-rc, with a list of all other available versions going back to 2.15.1, all with examples of overriding authentication.\u003c/p\u003e\n"],["\u003cp\u003eAuthentication is usually handled by Application Default Credentials, but you can use \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to set specific credentials, like those from a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for \u003ccode\u003edatastore_admin_v1::DatastoreAdminClient\u003c/code\u003e and \u003ccode\u003edatastore_v1::DatastoreClient\u003c/code\u003e, demonstrating how to load service account key files, which are easy to understand.\u003c/p\u003e\n"],["\u003cp\u003eBest practices for managing service account keys and more details on authentication are available via linked documentation, which include details on \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
