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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-07-09 UTC."],[[["This page details how to override default authentication credentials using `UnifiedCredentialsOption` in Google Cloud C++ client libraries, specifically in the context of versions 2.12.0 through 2.37.0-rc."],["The latest version available is 2.37.0-rc, with multiple prior releases listed, all the way back to version 2.12.0."],["The example demonstrates loading a service account key file to override the default Application Default Credentials for authentication with Google Cloud Services."],["Links to examples for other `*Client` classes like `CaseAttachmentServiceClient`, `CaseServiceClient`, and `CommentServiceClient` are provided for reference."],["It's crucial to review the \"Best practices for managing service account keys\" guide to ensure secure credential management."]]],[]]