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::apigateway_v1::ApiGatewayServiceClient(
google::cloud::apigateway_v1::MakeApiGatewayServiceConnection(options));
}
[[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-07-09 UTC."],[[["This page provides documentation for overriding default authentication credentials when using Google Cloud C++ client libraries to interact with the API Gateway service."],["The latest release candidate version is 2.37.0-rc, and this page also includes links to documentation for versions ranging from 2.36.0 down to 2.11.0."],["Users can override the default credentials by utilizing the `UnifiedCredentialsOption`, which is demonstrated using an example of loading a service account key file."],["The documentation links to resources for creating `google::cloud::Credentials` objects and to a guide on best practices for managing service account keys."]]],[]]
