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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 overriding default authentication credentials when using Google Cloud C++ client libraries, specifically for the Document AI service.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available is 2.37.0-rc, with a comprehensive list of prior versions back to 2.11.0 for the Document AI service.\u003c/p\u003e\n"],["\u003cp\u003eUsers can override the default Application Default Credentials by using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and providing a service account key file as shown in the given code snippet.\u003c/p\u003e\n"],["\u003cp\u003eThe provided code example demonstrates how to load credentials from a service account key file, which can be adapted for other scenarios based on the \u003ccode\u003eAuthentication Components\u003c/code\u003e documentation.\u003c/p\u003e\n"],["\u003cp\u003eIt's important to consult best practices for managing service account keys to ensure proper security when overriding authentication.\u003c/p\u003e\n"]]],[],null,[]]
