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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 most recent release candidate for data migration services is version 2.37.0-rc, with the latest stable version being 2.36.0, and previous versions going back to version 2.11.0 are documented.\u003c/p\u003e\n"],["\u003cp\u003eUsers can override the default Application Default Credentials (ADC) by utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and providing service account key file details.\u003c/p\u003e\n"],["\u003cp\u003eThe example code shows how to load credentials from a service account key file, but users should refer to the best practices guide for managing service account keys for more details.\u003c/p\u003e\n"],["\u003cp\u003eFor further details on the \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e object and related creation functions, please refer to the Authentication Components documentation.\u003c/p\u003e\n"]]],[],null,[]]
