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::automl_v1::AutoMlClient(
google::cloud::automl_v1::MakeAutoMlConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 past versions available for browsing, ranging back to version 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated in the provided C++ example for loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe example code demonstrates how to authenticate with \u003ccode\u003eAutoMlClient\u003c/code\u003e and \u003ccode\u003ePredictionServiceClient\u003c/code\u003e, but they should only be used as a very basic example, not considered best practice.\u003c/p\u003e\n"],["\u003cp\u003eThe page also has links to further information on managing service account keys and the authentication components used.\u003c/p\u003e\n"]]],[],null,[]]
