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::batch_v1::BatchServiceClient(
google::cloud::batch_v1::MakeBatchServiceConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 various versions of the C++ client library, ranging from version 2.11.0 to the latest release candidate 2.37.0-rc, for batch-override-authentication.\u003c/p\u003e\n"],["\u003cp\u003eThe client libraries primarily use Application Default Credentials for authentication with Google Cloud Services, unless otherwise configured.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication method by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated by explicitly loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example shows how to override the default credentials by reading the contents of a service account key file and configuring the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e accordingly.\u003c/p\u003e\n"],["\u003cp\u003eFor detailed information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, refer to the Authentication Components section.\u003c/p\u003e\n"]]],[],null,[]]
