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 of the documentation is for version 2.37.0-rc, and documentation is available for multiple previous versions, ranging down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eBy utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, users can override the default Application Default Credentials (ADC) and provide custom authentication methods, such as loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe document includes example code demonstrating how to explicitly load a service account key file and create a \u003ccode\u003eExecutionsClient\u003c/code\u003e with custom authentication.\u003c/p\u003e\n"],["\u003cp\u003eFor more information on managing service account keys and authentication components, refer to the linked best practices guide and the Authentication Components documentation.\u003c/p\u003e\n"]]],[],null,["Version 2.18.0keyboard_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/2.18.0/workflows_executions_v1_1_1ExecutionsClient-service-account-snippet)\n- [`workflows_v1::WorkflowsClient`](/cpp/docs/reference/workflows/2.18.0/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."]]