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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 in the Google Cloud C++ client libraries for various versions, from 2.11.0 to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe libraries typically use Application Default Credentials, but users can override this by supplying a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExample code demonstrates how to load a service account key file for the \u003ccode\u003eCaseAttachmentServiceClient\u003c/code\u003e and links are provided for the \u003ccode\u003eCaseServiceClient\u003c/code\u003e and \u003ccode\u003eCommentServiceClient\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eUsers are advised to consult the "Best practices for managing service account keys" guide for more in-depth information.\u003c/p\u003e\n"],["\u003cp\u003eA link is provided for further documentation regarding Authentication Components, including details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
