如何使用 Gmail API、OAuth2 for Apps 脚本和域范围委派为 G Suite 域中的用户设置电子邮件签名

这是我之前发布的问题/答案的后续内容（如何使用 Google 电子邮件设置 API 和 OAuth2 for Apps 脚本库为 Google Apps 域中的用户设置电子邮件签名 https://stackoverflow.com/questions/30135119/how-to-use-the-google-email-settings-api-and-the-oauth2-for-apps-script-library/），但我正在创建一个新问题，因为电子邮件设置API https://developers.google.com/admin-sdk/email-settings/已被弃用，现在的过程有很大不同。

作为 G Suite 域的管理员，您如何使用邮箱API https://developers.google.com/gmail/api/v1/reference/通过 Google Apps 脚本以编程方式设置您域中用户的电子邮件签名？

此方法使用 Gmail API、OAuth2 for Apps 脚本库和“域范围授权”，这是 G Suite 管理员代表其域内的用户进行 API 调用的一种方式。

Step 1:确保适用于应用程序脚本的 OAuth2 https://github.com/googlesamples/apps-script-oauth2库已添加到您的项目中。

Step 2:设置“域范围内的授权”。有一个页面here https://developers.google.com/drive/v2/web/delegation解释了如何为 Drive API 执行此操作，但对于任何 Google API（包括 Gmail API）来说几乎都是相同的。按照该页面上的步骤进行操作，直到“将域范围的权限委派给您的服务帐户”步骤（包括该步骤）。

Step 3:下面的代码包括如何在前面的步骤完成后设置签名：

function setSignatureTest() {

  var email = '[email protected] /cdn-cgi/l/email-protection';

  var signature = 'test signature';

  var test = setSignature(email, signature);

  Logger.log('test result: ' + test);

}


function setSignature(email, signature) {

  Logger.log('starting setSignature');

  var signatureSetSuccessfully = false;

  var service = getDomainWideDelegationService('Gmail: ', 'https://www.googleapis.com/auth/gmail.settings.basic', email);

  if (!service.hasAccess()) {

    Logger.log('failed to authenticate as user ' + email);

    Logger.log(service.getLastError());

    signatureSetSuccessfully = service.getLastError();

    return signatureSetSuccessfully;

  } else Logger.log('successfully authenticated as user ' + email);

  var username = email.split("@")[0];

  var resource = { signature: signature };

  var requestBody                = {};
  requestBody.headers            = {'Authorization': 'Bearer ' + service.getAccessToken()};
  requestBody.contentType        = "application/json";
  requestBody.method             = "PUT";
  requestBody.payload            = JSON.stringify(resource);
  requestBody.muteHttpExceptions = false;

  var emailForUrl = encodeURIComponent(email);

  var url = 'https://www.googleapis.com/gmail/v1/users/me/settings/sendAs/' + emailForUrl;

  var maxSetSignatureAttempts     = 20;
  var currentSetSignatureAttempts = 0;

  do {

    try {

      currentSetSignatureAttempts++;

      Logger.log('currentSetSignatureAttempts: ' + currentSetSignatureAttempts);

      var setSignatureResponse = UrlFetchApp.fetch(url, requestBody);

      Logger.log('setSignatureResponse on successful attempt:' + setSignatureResponse);

      signatureSetSuccessfully = true;

      break;

    } catch(e) {

      Logger.log('set signature failed attempt, waiting 3 seconds and re-trying');

      Utilities.sleep(3000);

    }

    if (currentSetSignatureAttempts >= maxSetSignatureAttempts) {

      Logger.log('exceeded ' + maxSetSignatureAttempts + ' set signature attempts, deleting user and ending script');

      throw new Error('Something went wrong when setting their email signature.');

    }

  } while (!signatureSetSuccessfully);

  return signatureSetSuccessfully;

}

// these two things are included in the .JSON file that you download when creating the service account and service account key
var OAUTH2_SERVICE_ACCOUNT_PRIVATE_KEY  = '-----BEGIN PRIVATE KEY-----\nxxxxxxxxxxxxxxxxxxxxx\n-----END PRIVATE KEY-----\n';
var OAUTH2_SERVICE_ACCOUNT_CLIENT_EMAIL = 'xxxxxxxxxxxxxxxxxxxxx.iam.gserviceaccount.com';


function getDomainWideDelegationService(serviceName, scope, email) {

  Logger.log('starting getDomainWideDelegationService for email: ' + email);

  return OAuth2.createService(serviceName + email)
      // Set the endpoint URL.
      .setTokenUrl('https://accounts.google.com/o/oauth2/token')

      // Set the private key and issuer.
      .setPrivateKey(OAUTH2_SERVICE_ACCOUNT_PRIVATE_KEY)
      .setIssuer(OAUTH2_SERVICE_ACCOUNT_CLIENT_EMAIL)

      // Set the name of the user to impersonate. This will only work for
      // Google Apps for Work/EDU accounts whose admin has setup domain-wide
      // delegation:
      // https://developers.google.com/identity/protocols/OAuth2ServiceAccount#delegatingauthority
      .setSubject(email)

      // Set the property store where authorized tokens should be persisted.
      .setPropertyStore(PropertiesService.getScriptProperties())

      // Set the scope. This must match one of the scopes configured during the
      // setup of domain-wide delegation.
      .setScope(scope);

}

请注意：do-while 循环与maxSetSignatureAttempts and currentSetSignatureAttempts变量不是必需的。我添加它是因为，如果您在创建 Google 帐户并分配 G Suite 许可证后尝试立即设置签名，有时 Gmail API 会返回错误，就好像用户尚未创建一样。如果出现错误，do-while 循环基本上会等待 3 秒，然后重试，最多 x 次。如果您为现有用户设置签名，则不应遇到此问题。另外，本来我只是固定10秒睡眠，但大多数时候不需要那么长时间，但其他时候仍然会失败。所以这个循环比固定的睡眠量要好。