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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 details how to override the default Application Default Credentials (ADC) for authenticating with Google Cloud Services using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version is 2.37.0-rc, and a range of previous versions from 2.36.0 down to 2.15.1 are documented here.\u003c/p\u003e\n"],["\u003cp\u003eAn example is given on how to load a service account key file using \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e, which is recommended to be used with the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e for overriding default credentials.\u003c/p\u003e\n"],["\u003cp\u003eLinks are provided to examples for other client classes, including \u003ccode\u003edatastore_admin_v1::DatastoreAdminClient\u003c/code\u003e and \u003ccode\u003edatastore_v1::DatastoreClient\u003c/code\u003e, that show how to make use of service accounts.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices on managing service account keys and other authentication component information, there are links to external guides.\u003c/p\u003e\n"]]],[],null,[]]
