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::trace_v1::TraceServiceClient(
google::cloud::trace_v1::MakeTraceServiceConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 various versions of the Google Cloud C++ client library, ranging from version 2.11.0 up to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe primary focus of this content is on how to override the default authentication credentials using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e in Google Cloud C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eBy providing a service account key file, users can explicitly load and utilize it for authentication, as shown in the provided C++ code example.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for both \u003ccode\u003etrace_v1::TraceServiceClient\u003c/code\u003e and \u003ccode\u003etrace_v2::TraceServiceClient\u003c/code\u003e classes on how to implement the service account override.\u003c/p\u003e\n"],["\u003cp\u003eUsers are directed to best practices for managing service account keys and are given a link to find out more about the factory functions used to create \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
