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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 default authentication method for the Document AI C++ client library is Application Default Credentials, however this default can be overwritten.\u003c/p\u003e\n"],["\u003cp\u003eOverriding default credentials involves utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to set specific credentials, such as those loaded from a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided code example demonstrates how to override authentication by explicitly loading a service account key file using \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e and setting it within the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices regarding managing service account keys and more information on creating \u003ccode\u003eCredentials\u003c/code\u003e objects, refer to the linked documentation on managing service account keys and authentication components.\u003c/p\u003e\n"]]],[],null,[]]
