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::datamigration_v1::DataMigrationServiceClient(
google::cloud::datamigration_v1::MakeDataMigrationServiceConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 overriding default authentication credentials when using Google Cloud client libraries, specifically focusing on data migration services.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available is 2.37.0-rc, with a comprehensive list of previous versions from 2.36.0 down to 2.11.0, and links for each version to the datamigration-override-authentication page.\u003c/p\u003e\n"],["\u003cp\u003eThe example code demonstrates how to load a service account key file to override the default Application Default Credentials (ADC).\u003c/p\u003e\n"],["\u003cp\u003eUsers can override the default credentials by utilizing \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and explicitly loading a service account key.\u003c/p\u003e\n"],["\u003cp\u003eFor more information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects and managing service account keys, refer to the provided links on Authentication Components and best practices.\u003c/p\u003e\n"]]],[],null,[]]
