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::networkconnectivity_v1::HubServiceClient(
google::cloud::networkconnectivity_v1::MakeHubServiceConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 documents the override authentication process for Google Cloud's Network Connectivity C++ client libraries, listing version-specific documentation, with the most recent being version \u003ccode\u003e2.37.0-rc\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe C++ client libraries use Application Default Credentials by default, but users can override this by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated by loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for overriding authentication in the \u003ccode\u003enetworkconnectivity_v1::HubServiceClient\u003c/code\u003e and \u003ccode\u003enetworkconnectivity_v1::PolicyBasedRoutingServiceClient\u003c/code\u003e classes in the \u003ccode\u003e2.35.0\u003c/code\u003e version.\u003c/p\u003e\n"],["\u003cp\u003eThe page also includes a link to the \u003ca href=\"https://cloud.google.com/iam/docs/best-practices-for-managing-service-account-keys\"\u003eBest practices for managing service account keys\u003c/a\u003e guide for more details on managing them.\u003c/p\u003e\n"],["\u003cp\u003eAdditional details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the \u003ca href=\"https://cloud.google.com/cpp/docs/reference/common/latest/group__guac.html\"\u003eAuthentication Components\u003c/a\u003e documentation.\u003c/p\u003e\n"]]],[],null,[]]
