Unless otherwise configured, the client libraries useApplication Default Credentialsto 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 theUnifiedCredentialsOptionThe 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::workflows_executions_v1::ExecutionsClient(
google::cloud::workflows_executions_v1::MakeExecutionsConnection(
options));
}
Follow these links to find examples for other*Clientclasses:
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-04 UTC."],[[["\u003cp\u003eThis document provides guidance on overriding default authentication credentials when interacting with Google Cloud services using C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available is 2.37.0-rc, and the page also contains information about all versions going back to 2.11.0 in this C++ context.\u003c/p\u003e\n"],["\u003cp\u003eBy using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, you can specify how to authenticate, including loading a service account key file, as shown in the provided example code snippet.\u003c/p\u003e\n"],["\u003cp\u003eThe document includes links to specific examples for \u003ccode\u003eworkflows_executions_v1::ExecutionsClient\u003c/code\u003e and \u003ccode\u003eworkflows_v1::WorkflowsClient\u003c/code\u003e to be used as references.\u003c/p\u003e\n"],["\u003cp\u003eIt's important to review best practices for service account key management, referenced in the provided link, when overriding default authentication.\u003c/p\u003e\n"]]],[],null,["Version 2.20.0keyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/workflows/latest/workflows-override-authentication)\n- [2.41.0](/cpp/docs/reference/workflows/2.41.0/workflows-override-authentication)\n- [2.40.0](/cpp/docs/reference/workflows/2.40.0/workflows-override-authentication)\n- [2.39.0](/cpp/docs/reference/workflows/2.39.0/workflows-override-authentication)\n- [2.38.0](/cpp/docs/reference/workflows/2.38.0/workflows-override-authentication)\n- [2.37.0](/cpp/docs/reference/workflows/2.37.0/workflows-override-authentication)\n- [2.36.0](/cpp/docs/reference/workflows/2.36.0/workflows-override-authentication)\n- [2.35.0](/cpp/docs/reference/workflows/2.35.0/workflows-override-authentication)\n- [2.34.0](/cpp/docs/reference/workflows/2.34.0/workflows-override-authentication)\n- [2.33.0](/cpp/docs/reference/workflows/2.33.0/workflows-override-authentication)\n- [2.32.0](/cpp/docs/reference/workflows/2.32.0/workflows-override-authentication)\n- [2.31.0](/cpp/docs/reference/workflows/2.31.0/workflows-override-authentication)\n- [2.30.0](/cpp/docs/reference/workflows/2.30.0/workflows-override-authentication)\n- [2.29.0](/cpp/docs/reference/workflows/2.29.0/workflows-override-authentication)\n- [2.28.0](/cpp/docs/reference/workflows/2.28.0/workflows-override-authentication)\n- [2.27.0](/cpp/docs/reference/workflows/2.27.0/workflows-override-authentication)\n- [2.26.0](/cpp/docs/reference/workflows/2.26.0/workflows-override-authentication)\n- [2.25.1](/cpp/docs/reference/workflows/2.25.1/workflows-override-authentication)\n- [2.24.0](/cpp/docs/reference/workflows/2.24.0/workflows-override-authentication)\n- [2.23.0](/cpp/docs/reference/workflows/2.23.0/workflows-override-authentication)\n- [2.22.1](/cpp/docs/reference/workflows/2.22.1/workflows-override-authentication)\n- [2.21.0](/cpp/docs/reference/workflows/2.21.0/workflows-override-authentication)\n- [2.20.0](/cpp/docs/reference/workflows/2.20.0/workflows-override-authentication)\n- [2.19.0](/cpp/docs/reference/workflows/2.19.0/workflows-override-authentication)\n- [2.18.0](/cpp/docs/reference/workflows/2.18.0/workflows-override-authentication)\n- [2.17.0](/cpp/docs/reference/workflows/2.17.0/workflows-override-authentication)\n- [2.16.0](/cpp/docs/reference/workflows/2.16.0/workflows-override-authentication)\n- [2.15.1](/cpp/docs/reference/workflows/2.15.1/workflows-override-authentication)\n- [2.14.0](/cpp/docs/reference/workflows/2.14.0/workflows-override-authentication)\n- [2.13.0](/cpp/docs/reference/workflows/2.13.0/workflows-override-authentication)\n- [2.12.0](/cpp/docs/reference/workflows/2.12.0/workflows-override-authentication)\n- [2.11.0](/cpp/docs/reference/workflows/2.11.0/workflows-override-authentication) \n\nHow to Override the Authentication Credentials\n==============================================\n\nUnless otherwise configured, the client libraries use [Application Default Credentials](https://cloud.google.com/docs/authentication#adc) 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](https://cloud.google.com/cpp/docs/reference/common/latest/structgoogle_1_1cloud_1_1UnifiedCredentialsOption.html) The following example shows how to explicitly load a service account key file: \n\n [](std::string const& keyfile) {\n auto is = std::ifstream(keyfile);\n is.exceptions(std::ios::badbit); // Minimal error handling in examples\n auto contents = std::string(std::istreambuf_iterator\u003cchar\u003e(is.rdbuf()), {});\n auto options =\n google::cloud::Options{}.set\u003cgoogle::cloud::UnifiedCredentialsOption\u003e(\n google::cloud::MakeServiceAccountCredentials(contents));\n return google::cloud::workflows_executions_v1::ExecutionsClient(\n google::cloud::workflows_executions_v1::MakeExecutionsConnection(\n options));\n }\n\nFollow these links to find examples for other `*Client` classes:\n\n- [`workflows_executions_v1::ExecutionsClient`](/cpp/docs/reference/workflows/2.20.0/workflows_executions_v1_1_1ExecutionsClient-service-account-snippet)\n- [`workflows_v1::WorkflowsClient`](/cpp/docs/reference/workflows/2.20.0/workflows_v1_1_1WorkflowsClient-service-account-snippet)\n\nKeep in mind that we chose this as an example because it is relatively easy to understand. Consult the [Best practices for managing service account keys](https://cloud.google.com/iam/docs/best-practices-for-managing-service-account-keys) guide for more details.\n\n###### See Also\n\n[Authentication Components](https://cloud.google.com/cpp/docs/reference/common/latest/group__guac.html) - for more information on the factory functions to create [`google::cloud::Credentials`](https://cloud.google.com/cpp/docs/reference/common/latest/classgoogle_1_1cloud_1_1Credentials.html) objects."]]