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"]],[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version available is 2.37.0-rc, with numerous preceding versions down to 2.12.0 also listed.\u003c/p\u003e\n"],["\u003cp\u003eThe client libraries default to using Application Default Credentials (ADC) for authentication with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by providing a UnifiedCredentialsOption, such as loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe example uses a service account key file to demonstrate how to override default authentication credentials, but users are advised to refer to the best practices guide for service account key management.\u003c/p\u003e\n"],["\u003cp\u003eThe Authentication Components page can be consulted for additional information on creating Credentials objects.\u003c/p\u003e\n"]]],[],null,[]]
