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::datafusion_v1::DataFusionClient(
google::cloud::datafusion_v1::MakeDataFusionConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis page provides documentation for overriding default authentication credentials when interacting with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eThe content demonstrates how to load a service account key file using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to override the default Application Default Credentials.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version of the documentation is \u003ccode\u003e2.37.0-rc\u003c/code\u003e, with multiple prior versions available, down to \u003ccode\u003e2.13.0\u003c/code\u003e, each providing similar instructions for overriding authentication.\u003c/p\u003e\n"],["\u003cp\u003eFor security considerations and more information, it recommends consulting the "Best practices for managing service account keys" guide.\u003c/p\u003e\n"],["\u003cp\u003eAdditional information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the "Authentication Components" section.\u003c/p\u003e\n"]]],[],null,[]]
