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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 latest release candidate version is 2.37.0-rc, and version 2.36.0 is the most recent full release.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries generally use Application Default Credentials for Google Cloud service authentication, but you can override this.\u003c/p\u003e\n"],["\u003cp\u003eAuthentication can be overridden by providing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and loading a service account key file explicitly.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003edatastore_admin_v1::DatastoreAdminClient\u003c/code\u003e and the \u003ccode\u003edatastore_v1::DatastoreClient\u003c/code\u003e are examples of clients where these overrides are possible.\u003c/p\u003e\n"],["\u003cp\u003eConsult the "Best practices for managing service account keys" guide for details on managing service accounts.\u003c/p\u003e\n"]]],[],null,[]]
