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::bigquerycontrol_v2::DatasetServiceClient(
google::cloud::bigquerycontrol_v2::MakeDatasetServiceConnectionRest(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 how to override the default Application Default Credentials (ADC) for authenticating with Google Cloud Services using the C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eOverriding the default credentials can be achieved by providing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated with an example of loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version is \u003ccode\u003e2.37.0-rc\u003c/code\u003e, however this document uses \u003ccode\u003e2.29.0\u003c/code\u003e to provide working examples.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for various \u003ccode\u003e*Client\u003c/code\u003e classes, including \u003ccode\u003eDatasetServiceClient\u003c/code\u003e, \u003ccode\u003eJobServiceClient\u003c/code\u003e, and others, within the \u003ccode\u003ebigquerycontrol_v2\u003c/code\u003e namespace.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices on managing service account keys and further information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, refer to the linked resources.\u003c/p\u003e\n"]]],[],null,[]]
