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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 documentation focuses on using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to specify custom authentication, such as loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version is 2.37.0-rc, and the page includes links for numerous previous versions, from 2.36.0 down to 2.13.0.\u003c/p\u003e\n"],["\u003cp\u003eDefault credentials are used unless custom configuration is applied, and the provided example demonstrates loading credentials from a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe page provides a link to the best practices for managing service account keys and also to the Authentication Components for further information on creating credentials.\u003c/p\u003e\n"]]],[],null,[]]
