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::documentai_v1::DocumentProcessorServiceClient(
google::cloud::documentai_v1::MakeDocumentProcessorServiceConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThis page documents the available versions of the Document AI 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 C++ client libraries use Application Default Credentials for authentication, but you can override this default behavior.\u003c/p\u003e\n"],["\u003cp\u003eTo override the default, you can use the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, such as by loading a service account key file as demonstrated in the example.\u003c/p\u003e\n"],["\u003cp\u003eFor detailed information on managing service account keys, refer to the "Best practices for managing service account keys" guide.\u003c/p\u003e\n"],["\u003cp\u003eYou can find more details on the factory functions that create \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects in the Authentication Components documentation.\u003c/p\u003e\n"]]],[],null,[]]
