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"]],[["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 2025-08-14 UTC."],[[["\u003cp\u003eThe latest version for data migration documentation is 2.37.0-rc, with previous versions available from 2.36.0 down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eBy default, client libraries authenticate with Google Cloud Services using Application Default Credentials, but you can override this.\u003c/p\u003e\n"],["\u003cp\u003eTo override default credentials, you can use the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, such as explicitly loading a service account key file, for which an example is given.\u003c/p\u003e\n"],["\u003cp\u003eFor details on managing service account keys, you can consult the "Best practices for managing service account keys" guide.\u003c/p\u003e\n"],["\u003cp\u003eFurther details on factory functions for creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects are available in the Authentication Components section.\u003c/p\u003e\n"]]],[],null,[]]
