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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version available is 2.37.0-rc, with links provided for all available versions from 2.37.0-rc down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eBy default, client libraries use Application Default Credentials for authentication with Google Cloud Services, but this can be overridden when necessary.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by utilizing the UnifiedCredentialsOption, as demonstrated in the provided code example using a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example demonstrates overriding authentication by explicitly loading a service account key file, which can be adapted for other cases where needed.\u003c/p\u003e\n"],["\u003cp\u003eThe Authentication Components link provides further information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
