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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 webpage 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 for the client libraries uses Application Default Credentials, but can be overridden when needed.\u003c/p\u003e\n"],["\u003cp\u003eOverriding the default authentication can be done by setting the \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, it is recommended to consult the "Best practices for managing service account keys" guide.\u003c/p\u003e\n"],["\u003cp\u003eThe "Authentication Components" documentation provides further information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects using factory functions.\u003c/p\u003e\n"]]],[],null,[]]
