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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 documents how to override the default Application Default Credentials (ADC) used by client libraries for authenticating with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version for this documentation is 2.37.0-rc, while version 2.17.0 is highlighted with links to \u003ccode\u003esupport_v2::CaseAttachmentServiceClient\u003c/code\u003e, \u003ccode\u003esupport_v2::CaseServiceClient\u003c/code\u003e and \u003ccode\u003esupport_v2::CommentServiceClient\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eTo override default credentials, you can use \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and load a service account key file as shown in the example code.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for several \u003ccode\u003e*Client\u003c/code\u003e classes, including \u003ccode\u003esupport_v2::CaseAttachmentServiceClient\u003c/code\u003e, \u003ccode\u003esupport_v2::CaseServiceClient\u003c/code\u003e, and \u003ccode\u003esupport_v2::CommentServiceClient\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe provided documentation also advises to consult the guide to best practices for managing service account keys for more information, and the authentication components page.\u003c/p\u003e\n"]]],[],null,[]]
