Cómo autorizar solicitudes

    public static void main(String[] args) {
      try {
        httpTransport = GoogleNetHttpTransport.newTrustedTransport();
        dataStoreFactory = new FileDataStoreFactory(DATA_STORE_DIR);
        jsonFactory = JacksonFactory.getDefaultInstance();
        scopes =  "https://www.googleapis.com/auth/manufacturercenter";

        // load configuration
        File configPath = new File(basePath, "manufacturers");
        File configFile = new File(configPath, manufacturers-info.json);
        ManufacturersConfig config = new JacksonFactory().fromInputStream(inputStream, ManufacturersConfig.class);
        config.setPath(configPath);

        // Get authorization token
        Credential credential = authenticate(httpTransport, dataStoreFactory, config, jsonFactory, scopes);
        // ...
      }
    }

    private static Credential authenticate(httpTransport, dataStoreFactory, config, jsonFactory, scopes) throws Exception {
      try {
        Credential credential = GoogleCredential.getApplicationDefault().createScoped(scopes);
        System.out.println("Loaded the Application Default Credentials.");
        return credential;
      } catch (IOException e) {
        // No need to do anything, we'll fall back on other credentials.
      }
      if (config.getPath() == null) {
        throw new IllegalArgumentException(
            "Must use Application Default Credentials with no configuration directory.");
      }
      File clientSecretsFile = new File(config.getPath(), "client-secrets.json");
      if (clientSecretsFile.exists()) {
        System.out.println("Loading OAuth2 client credentials.");
        try (InputStream inputStream = new FileInputStream(clientSecretsFile)) {
          GoogleClientSecrets clientSecrets =
              GoogleClientSecrets.load(jsonFactory, new InputStreamReader(inputStream));
          // set up authorization code flow
          GoogleAuthorizationCodeFlow flow =
              new GoogleAuthorizationCodeFlow.Builder(
                      httpTransport, jsonFactory, clientSecrets, scopes)
                  .setDataStoreFactory(dataStoreFactory)
                  .build();
          // authorize
          String userID = ConfigDataStoreFactory.UNUSED_ID;
          Credential storedCredential = flow.loadCredential(userID);
          if (storedCredential != null) {
            System.out.printf("Retrieved stored credential for %s from cache.%n", userID);
            return storedCredential;
          }
          LocalServerReceiver receiver =
              new LocalServerReceiver.Builder().setHost("localhost").setPort(9999).build();
          Credential credential = new AuthorizationCodeInstalledApp(flow, receiver).authorize(userID);
          System.out.printf("Retrieved credential for %s from web.%n", userID);
          return credential;
        } catch (IOException e) {
          throw new IOException(
              "Could not retrieve OAuth2 client credentials from the file "

                                    +   clientSecretsFile.getCanonicalPath());
        }
      }
      throw new IOException(
          "No authentication credentials found. Checked the Google Application"
                            +   "Default Credentials and the paths "
                            +   clientSecretsFile.getCanonicalPath()
                            +   ". Please read the accompanying README.");
    }