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::essentialcontacts_v1::EssentialContactsServiceClient(
google::cloud::essentialcontacts_v1::
MakeEssentialContactsServiceConnection(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 of the Essential Contacts API is 2.37.0-rc, while multiple other versions are also available, including 2.36.0, 2.35.0, and down to 2.12.0.\u003c/p\u003e\n"],["\u003cp\u003eBy default, the client libraries utilize Application Default Credentials (ADC) for authentication with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, allowing for custom credential loading.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example demonstrates how to explicitly load a service account key file for authentication, via the \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e function.\u003c/p\u003e\n"],["\u003cp\u003eFor further details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, the "Authentication Components" link can be consulted.\u003c/p\u003e\n"]]],[],null,[]]
