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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 provides documentation for various 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 client libraries use Application Default Credentials for authentication with Google Cloud Services by default, but this can be overridden if necessary.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and loading a service account key file, as demonstrated in the provided example.\u003c/p\u003e\n"],["\u003cp\u003eThe "Best practices for managing service account keys" guide is recommended for more information on the subject.\u003c/p\u003e\n"],["\u003cp\u003eThe "Authentication Components" section provides details on factory functions to create \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects for authentication.\u003c/p\u003e\n"]]],[],null,[]]
