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::retail_v2::AnalyticsServiceClient(
google::cloud::retail_v2::MakeAnalyticsServiceConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-07-09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 the default Application Default Credentials (ADC) for authenticating with Google Cloud Services using the C++ client libraries, offering a method for explicitly loading a service account key file."],["Version-specific documentation is available, ranging from version 2.11.0 up to the latest release candidate, 2.37.0-rc, along with a variety of links to examples for other client classes."],["The page provides code examples demonstrating how to use `UnifiedCredentialsOption` and `MakeServiceAccountCredentials` to set custom authentication options."],["Specific examples are provided for multiple `retail_v2` client classes, including AnalyticsServiceClient, CatalogServiceClient, and SearchServiceClient, amongst others."],["There is a link to the Best practices guide for managing service account keys for more information on the topic, and the Authentication Components link leads to more information on creating credentials."]]],[]]
