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::channel_v1::CloudChannelServiceClient(
google::cloud::channel_v1::MakeCloudChannelServiceConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 interacting with Google Cloud Services, using version 2.35.0 as the current base version.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version is 2.37.0-rc, and the page lists previous versions down to 2.11.0, with each link pertaining to overriding authentication credentials.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries generally utilize Application Default Credentials, but developers can use \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to specify alternative authentication methods, such as a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003echannel_v1::CloudChannelServiceClient\u003c/code\u003e and \u003ccode\u003echannel_v1::CloudChannelReportsServiceClient\u003c/code\u003e classes provide specific examples for overriding authentication, and best practices can be found in the managing service account keys guide.\u003c/p\u003e\n"],["\u003cp\u003eFor additional information regarding the creation of \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, the Authentication Components documentation is also provided.\u003c/p\u003e\n"]]],[],null,[]]
