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::bigquery_analyticshub_v1::AnalyticsHubServiceClient(
google::cloud::bigquery_analyticshub_v1::
MakeAnalyticsHubServiceConnection(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 page provides documentation for overriding default authentication credentials when using Google Cloud C++ client libraries with BigQuery services.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release of the BigQuery C++ client library is version 2.37.0-rc, while version 2.22.1 is being viewed in the list of available versions ranging back to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eUsers can override the default Application Default Credentials by utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, such as loading a service account key file, as shown in the example.\u003c/p\u003e\n"],["\u003cp\u003eLinks are provided for various BigQuery client classes, which will show examples on how to override authentication, including \u003ccode\u003eAnalyticsHubServiceClient\u003c/code\u003e, \u003ccode\u003eMetastoreServiceClient\u003c/code\u003e, \u003ccode\u003eConnectionServiceClient\u003c/code\u003e, and others.\u003c/p\u003e\n"],["\u003cp\u003eThere is a link to the guide on the best practices for managing service account keys, and another link to authentication components for more information on the factory functions to create credentials.\u003c/p\u003e\n"]]],[],null,["Version 2.22.1keyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/bigquery/latest/bigquery-override-authentication)\n- [2.41.0](/cpp/docs/reference/bigquery/2.41.0/bigquery-override-authentication)\n- [2.40.0](/cpp/docs/reference/bigquery/2.40.0/bigquery-override-authentication)\n- [2.39.0](/cpp/docs/reference/bigquery/2.39.0/bigquery-override-authentication)\n- [2.38.0](/cpp/docs/reference/bigquery/2.38.0/bigquery-override-authentication)\n- [2.37.0](/cpp/docs/reference/bigquery/2.37.0/bigquery-override-authentication)\n- [2.36.0](/cpp/docs/reference/bigquery/2.36.0/bigquery-override-authentication)\n- [2.35.0](/cpp/docs/reference/bigquery/2.35.0/bigquery-override-authentication)\n- [2.34.0](/cpp/docs/reference/bigquery/2.34.0/bigquery-override-authentication)\n- [2.33.0](/cpp/docs/reference/bigquery/2.33.0/bigquery-override-authentication)\n- [2.32.0](/cpp/docs/reference/bigquery/2.32.0/bigquery-override-authentication)\n- [2.31.0](/cpp/docs/reference/bigquery/2.31.0/bigquery-override-authentication)\n- [2.30.0](/cpp/docs/reference/bigquery/2.30.0/bigquery-override-authentication)\n- [2.29.0](/cpp/docs/reference/bigquery/2.29.0/bigquery-override-authentication)\n- [2.28.0](/cpp/docs/reference/bigquery/2.28.0/bigquery-override-authentication)\n- [2.27.0](/cpp/docs/reference/bigquery/2.27.0/bigquery-override-authentication)\n- [2.26.0](/cpp/docs/reference/bigquery/2.26.0/bigquery-override-authentication)\n- [2.25.1](/cpp/docs/reference/bigquery/2.25.1/bigquery-override-authentication)\n- [2.24.0](/cpp/docs/reference/bigquery/2.24.0/bigquery-override-authentication)\n- [2.23.0](/cpp/docs/reference/bigquery/2.23.0/bigquery-override-authentication)\n- [2.22.1](/cpp/docs/reference/bigquery/2.22.1/bigquery-override-authentication)\n- [2.21.0](/cpp/docs/reference/bigquery/2.21.0/bigquery-override-authentication)\n- [2.20.0](/cpp/docs/reference/bigquery/2.20.0/bigquery-override-authentication)\n- [2.19.0](/cpp/docs/reference/bigquery/2.19.0/bigquery-override-authentication)\n- [2.18.0](/cpp/docs/reference/bigquery/2.18.0/bigquery-override-authentication)\n- [2.17.0](/cpp/docs/reference/bigquery/2.17.0/bigquery-override-authentication)\n- [2.16.0](/cpp/docs/reference/bigquery/2.16.0/bigquery-override-authentication)\n- [2.15.1](/cpp/docs/reference/bigquery/2.15.1/bigquery-override-authentication)\n- [2.14.0](/cpp/docs/reference/bigquery/2.14.0/bigquery-override-authentication)\n- [2.13.0](/cpp/docs/reference/bigquery/2.13.0/bigquery-override-authentication)\n- [2.12.0](/cpp/docs/reference/bigquery/2.12.0/bigquery-override-authentication)\n- [2.11.0](/cpp/docs/reference/bigquery/2.11.0/bigquery-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::bigquery_analyticshub_v1::AnalyticsHubServiceClient(\n google::cloud::bigquery_analyticshub_v1::\n MakeAnalyticsHubServiceConnection(options));\n }\n\nFollow these links to find examples for other `*Client` classes:\n\n- [`bigquery_analyticshub_v1::AnalyticsHubServiceClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_analyticshub_v1_1_1AnalyticsHubServiceClient-service-account-snippet)\n- [`bigquery_biglake_v1::MetastoreServiceClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_biglake_v1_1_1MetastoreServiceClient-service-account-snippet)\n- [`bigquery_connection_v1::ConnectionServiceClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_connection_v1_1_1ConnectionServiceClient-service-account-snippet)\n- [`bigquery_datapolicies_v1::DataPolicyServiceClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_datapolicies_v1_1_1DataPolicyServiceClient-service-account-snippet)\n- [`bigquery_datatransfer_v1::DataTransferServiceClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_datatransfer_v1_1_1DataTransferServiceClient-service-account-snippet)\n- [`bigquery_migration_v2::MigrationServiceClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_migration_v2_1_1MigrationServiceClient-service-account-snippet)\n- [`bigquery_reservation_v1::ReservationServiceClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_reservation_v1_1_1ReservationServiceClient-service-account-snippet)\n- [`bigquery_storage_v1::BigQueryReadClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_storage_v1_1_1BigQueryReadClient-service-account-snippet)\n- [`bigquery_storage_v1::BigQueryWriteClient`](/cpp/docs/reference/bigquery/2.22.1/bigquery_storage_v1_1_1BigQueryWriteClient-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."]]