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::accesscontextmanager_v1::AccessContextManagerClient(
google::cloud::accesscontextmanager_v1::
MakeAccessContextManagerConnection(options));
}
[[["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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version of the Access Context Manager documentation is 2.37.0-rc, and the page provides links to documentation for several previous versions down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eThe client libraries typically authenticate with Google Cloud Services using Application Default Credentials, but you can override this default.\u003c/p\u003e\n"],["\u003cp\u003eOverriding the default authentication can be done by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated with an example that explicitly loads a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eFor details on managing service account keys, consult the "Best practices for managing service account keys" guide.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ca href=\"https://cloud.google.com/cpp/docs/reference/common/latest/group__guac.html\"\u003eAuthentication Components\u003c/a\u003e page will provide you with more information about the functions used to make the \u003ca href=\"https://cloud.google.com/cpp/docs/reference/common/latest/classgoogle_1_1cloud_1_1Credentials.html\"\u003e\u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e\u003c/a\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
