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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 webpage provides documentation for various versions of the Data Migration service, ranging from version 2.11.0 up to the latest release candidate, 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication method for client libraries is Application Default Credentials, but this can be overridden using the UnifiedCredentialsOption.\u003c/p\u003e\n"],["\u003cp\u003eAn example is provided demonstrating how to override the default credentials by explicitly loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eBest practices for managing service account keys can be found in the linked guide for more details.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ca href=\"https://cloud.google.com/cpp/docs/reference/common/latest/group__guac.html\"\u003eAuthentication Components\u003c/a\u003e page provides additional information for the factory functions that create credential objects.\u003c/p\u003e\n"]]],[],null,[]]
