Override the authentication configuration

Some applications cannot use the default authentication mechanism (known as [Application Default Credentials]). You can override this default usinggoogle::cloud::UnifiedCredentialsOption. The following example shows how to explicitly load a service account key file.

  namespace spanner = ::google::cloud::spanner;  [](std::string const& project_id, std::string const& instance_id,     std::string const& database_id, std::string const& keyfile) {    auto is = std::ifstream(keyfile);    is.exceptions(std::ios::badbit);    auto contents = std::string(std::istreambuf_iterator<char>(is.rdbuf()), {});    auto options =        google::cloud::Options{}.set<google::cloud::UnifiedCredentialsOption>(            google::cloud::MakeServiceAccountCredentials(contents));    return spanner::Client(spanner::MakeConnection(        spanner::Database(project_id, instance_id, database_id), options));  }

Keep in mind that we chose this as an example because it is relatively easy to understand. Consult the [Best practices for managing service account keys] guide for more details.

Follow these links to find examples for other*Client classes:

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Last updated 2025-12-18 UTC.