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::support_v2::CaseAttachmentServiceClient(
google::cloud::support_v2::MakeCaseAttachmentServiceConnection(
options));
}
Follow these links to find examples for other *Client classes:
[[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 page provides documentation for overriding default authentication credentials when using Google Cloud client libraries, with version 2.20.0 being the focused version.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication method utilizes Application Default Credentials, but you can provide a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to override this.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example demonstrates how to load authentication details using a service account key file, which you can then set as the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eSpecific examples for overriding service accounts can be found for \u003ccode\u003esupport_v2::CaseAttachmentServiceClient\u003c/code\u003e, \u003ccode\u003esupport_v2::CaseServiceClient\u003c/code\u003e, and \u003ccode\u003esupport_v2::CommentServiceClient\u003c/code\u003e classes, all located on version 2.20.0 of the documentation.\u003c/p\u003e\n"],["\u003cp\u003eThe page contains links to versioned references for a variety of supported releases, from 2.11.0 up to the latest release candidate at 2.37.0-rc, for these override methods.\u003c/p\u003e\n"]]],[],null,[]]
