具有公共访问权限的Web应用程序的Google OAuth 2.0刷新令牌

我收到以下错误：

OAuth 2.0访问令牌已过期，并且刷新令牌不可用。对于自动批准的响应，不返回刷新令牌

我有一个仅允许我的服务器访问的Web应用程序，初始身份验证工作正常，但是一个小时后，上述错误消息弹出。我的脚本如下所示：

require_once 'Google/Client.php';     
require_once 'Google/Service/Analytics.php';       
session_start();

$client = new Google_Client();
$client->setApplicationName("Client_Library_Examples");
$client->setDeveloperKey("{MY_API_KEY}");
$client->setClientId('{MY_CLIENT_ID}.apps.googleusercontent.com');
$client->setClientSecret('{MY_KEY}');
$client->setRedirectUri('{MY_REDIRECT_URI}');
$client->setScopes(array('https://www.googleapis.com/auth/gmail.readonly'));

if (isset($_GET['code'])) {
    $client->authenticate($_GET['code']);  
    $_SESSION['token'] = $client->getAccessToken();
    $redirect = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'];
    header('Location: ' . filter_var($redirect, FILTER_SANITIZE_URL));
}

if (!$client->getAccessToken() && !isset($_SESSION['token'])) {
    $authUrl = $client->createAuthUrl();
    print "<a class='login' href='$authUrl'>Connect Me!</a>";
}

如何为此设置刷新令牌？

编辑1：我也尝试过使用服务帐户执行此操作。我遵循了GitHub上可用的文档：

https://github.com/google/google-api-php-client/blob/master/examples/service-account.php

我的脚本如下所示：

session_start();
include_once "templates/base.php";
require_once 'Google/Client.php';
require_once 'Google/Service/Gmail.php';
$client_id = '{MY_CLIENT_ID}.apps.googleusercontent.com'; 
$service_account_name = '{MY_EMAIL_ADDRESS}@developer.gserviceaccount.com ';
$key_file_location = 'Google/{MY_KEY_FILE}.p12';
echo pageHeader("Service Account Access");
    if ($client_id == ''
|| !strlen($service_account_name)
|| !strlen($key_file_location)) {
  echo missingServiceAccountDetailsWarning();
}
$client = new Google_Client();
$client->setApplicationName("Client_Library_Examples");
$service = new Google_Service_Gmail($client);
if (isset($_SESSION['service_token'])) {
  $client->setAccessToken($_SESSION['service_token']);
}
$key = file_get_contents($key_file_location);
$cred = new Google_Auth_AssertionCredentials(
    $service_account_name,
    array('https://www.googleapis.com/auth/gmail.readonly'),
    $key
);
$client->setAssertionCredentials($cred);
if($client->getAuth()->isAccessTokenExpired()) {
  $client->getAuth()->refreshTokenWithAssertion($cred);
}

这将返回以下消息：

刷新OAuth2令牌时出错，消息：'{“错误”：“ invalid_grant”}''

跟踪此代码的源代码后，可以在 Google/Auth/OAuth2.php

有问题的方法refreshTokenRequest：

private function refreshTokenRequest($params)
{
    $http = new Google_Http_Request(
    self::OAUTH2_TOKEN_URI,
    'POST',
    array(),
    $params
    );
    $http->disableGzip();
    $request = $this->client->getIo()->makeRequest($http);

    $code = $request->getResponseHttpCode();
    $body = $request->getResponseBody();
    if (200 == $code) {
      $token = json_decode($body, true);
      if ($token == null) {
        throw new Google_Auth_Exception("Could not json decode the access token");
      }

      if (! isset($token['access_token']) || ! isset($token['expires_in']))     {
        throw new Google_Auth_Exception("Invalid token format");
      }

      if (isset($token['id_token'])) {
        $this->token['id_token'] = $token['id_token'];
      }
      $this->token['access_token'] = $token['access_token'];
      $this->token['expires_in'] = $token['expires_in'];
      $this->token['created'] = time();
    } else {
      throw new Google_Auth_Exception("Error refreshing the OAuth2 token, message: '$body'", $code);
    }
  }

这意味着该$code变量为NULL。我在SO上找到了这篇文章：

刷新OAuth2令牌时发生错误{“错误”：“ invalid_grant”}

可以看到仍然没有首选的解决方案。这让我发疯。关于这一点的文档很少甚至没有，如果有人有解决方案，我敢肯定我不是唯一寻求它的人。