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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe client libraries default to using Application Default Credentials for Google Cloud Services authentication, but this can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eYou can override default credentials by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, for example, by loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example demonstrates overriding credentials by loading a service account key file and creating an options instance.\u003c/p\u003e\n"],["\u003cp\u003eExamples for other client classes like \u003ccode\u003edatastore_admin_v1::DatastoreAdminClient\u003c/code\u003e and \u003ccode\u003edatastore_v1::DatastoreClient\u003c/code\u003e are also available.\u003c/p\u003e\n"],["\u003cp\u003eRefer to the "Best practices for managing service account keys" guide and the "Authentication Components" section for detailed information on managing credentials.\u003c/p\u003e\n"]]],[],null,[]]
