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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThis webpage provides documentation for various versions of the C++ Essential Contacts client library, ranging from version 2.12.0 up to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe client libraries default to using Application Default Credentials for Google Cloud Service authentication, but this can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by utilizing the UnifiedCredentialsOption and providing credentials, such as loading a service account key file, demonstrated by an example in the content.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices on service account key management and additional details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, refer to the linked guides on managing service account keys and authentication components.\u003c/p\u003e\n"]]],[],null,[]]
