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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 details how to override the default authentication credentials used by the client libraries when interacting with Google Cloud Services, which typically rely on Application Default Credentials.\u003c/p\u003e\n"],["\u003cp\u003eThe most recent release candidate version is 2.37.0-rc, while the latest stable release is 2.36.0, with a range of versions from 2.11.0 up to the most current listed for review.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by providing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, such as loading a service account key file explicitly.\u003c/p\u003e\n"],["\u003cp\u003eThe example code demonstrates how to load a service account key file using \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e and set it within \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eFor further details on managing service account keys, see the recommended guide, and the Authentication Components page for information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
