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 2025-08-01 UTC."],[[["The latest version for data migration documentation is 2.37.0-rc, with previous versions available from 2.36.0 down to 2.11.0."],["By default, client libraries authenticate with Google Cloud Services using Application Default Credentials, but you can override this."],["To override default credentials, you can use the `UnifiedCredentialsOption`, such as explicitly loading a service account key file, for which an example is given."],["For details on managing service account keys, you can consult the \"Best practices for managing service account keys\" guide."],["Further details on factory functions for creating `google::cloud::Credentials` objects are available in the Authentication Components section."]]],[]]
