从您的应用后端访问 Google API

如果您希望服务器能够 代表用户调用 Google API，或在用户离线时调用 Google API。

准备工作

您必须完成基本的 Google 登录功能集成。

为应用启用服务器端 API 访问权限

在在 iOS 应用中访问 Google API 页面上 页面上，您的应用仅在客户端对用户进行身份验证；在本例中 您的应用只能在用户正在使用 。

按照本页介绍的程序，您的服务器就可以将 Google API 在用户离线时代表用户进行通话。例如，照片应用可以 通过在后端进行处理，增强用户 Google 相册影集中的照片 并将结果上传到其他影集。为此，您的服务器 需要访问令牌和刷新令牌。

要获取服务器的访问令牌和刷新令牌，您可以执行以下操作： 请求您的服务器用来交换的一次性授权代码 生成这两个词元。成功登录后，您会发现一次性代码为 GIDSignInResult 的 serverAuthCode 属性。

  1. 获取服务器客户端 ID（如果尚未获取） 并在应用的 Info.plist 文件中（位于 OAuth 客户端 ID 下方）进行指定。

    <key>GIDServerClientID</key>
<string>YOUR_SERVER_CLIENT_ID</string>

  2. 在您的登录回调中，检索一次性授权代码：

    Swift

    GIDSignIn.sharedInstance.signIn(withPresenting: self) { signInResult, error in
    guard error == nil else { return }
    guard let signInResult = signInResult else { return }

    let authCode = signInResult.serverAuthCode
}

    Objective-C

    [GIDSignIn.sharedInstance
          signInWithPresentingViewController:self
                                  completion:^(GIDSignInResult * _Nullable signInResult,
                                               NSError * _Nullable error) {
      if (error) { return; }
      if (signInResult == nil) { return; }

      NSString *authCode = signInResult.serverAuthCode;
}];

  3. 使用 HTTPS POST 将 serverAuthCode 字符串安全地传递到您的服务器。

  4. 在应用的后端服务器上，使用授权代码获取访问权限并刷新 词元。使用访问令牌以用户的名义调用 Google API； 存储刷新令牌，以便在 访问令牌到期。

    例如：

    Java
    // (Receive authCode via HTTPS POST)


if (request.getHeader("X-Requested-With") == null) {
  // Without the `X-Requested-With` header, this request could be forged. Aborts.
}

// Set path to the Web application client_secret_*.json file you downloaded from the
// Google API Console: https://console.cloud.google.com/apis/credentials
// You can also find your Web application client ID and client secret from the
// console and specify them directly when you create the GoogleAuthorizationCodeTokenRequest
// object.
String CLIENT_SECRET_FILE = "/path/to/client_secret.json";

// Exchange auth code for access token
GoogleClientSecrets clientSecrets =
    GoogleClientSecrets.load(
        JacksonFactory.getDefaultInstance(), new FileReader(CLIENT_SECRET_FILE));
GoogleTokenResponse tokenResponse =
          new GoogleAuthorizationCodeTokenRequest(
              new NetHttpTransport(),
              JacksonFactory.getDefaultInstance(),
              "https://oauth2.googleapis.com/token",
              clientSecrets.getDetails().getClientId(),
              clientSecrets.getDetails().getClientSecret(),
              authCode,
              REDIRECT_URI)  // Specify the same redirect URI that you use with your web
                             // app. If you don't have a web version of your app, you can
                             // specify an empty string.
              .execute();

String accessToken = tokenResponse.getAccessToken();

// Use access token to call API
GoogleCredential credential = new GoogleCredential().setAccessToken(accessToken);
Drive drive =
    new Drive.Builder(new NetHttpTransport(), JacksonFactory.getDefaultInstance(), credential)
        .setApplicationName("Auth Code Exchange Demo")
        .build();
File file = drive.files().get("appfolder").execute();

// Get profile info from ID token
GoogleIdToken idToken = tokenResponse.parseIdToken();
GoogleIdToken.Payload payload = idToken.getPayload();
String userId = payload.getSubject();  // Use this value as a key to identify a user.
String email = payload.getEmail();
boolean emailVerified = Boolean.valueOf(payload.getEmailVerified());
String name = (String) payload.get("name");
String pictureUrl = (String) payload.get("picture");
String locale = (String) payload.get("locale");
String familyName = (String) payload.get("family_name");
String givenName = (String) payload.get("given_name");
    Python
    from apiclient import discovery
import httplib2
from oauth2client import client

# (Receive auth_code by HTTPS POST)


# If this request does not have `X-Requested-With` header, this could be a CSRF
if not request.headers.get('X-Requested-With'):
    abort(403)

# Set path to the Web application client_secret_*.json file you downloaded from the
# Google API Console: https://console.cloud.google.com/apis/credentials
CLIENT_SECRET_FILE = '/path/to/client_secret.json'

# Exchange auth code for access token, refresh token, and ID token
credentials = client.credentials_from_clientsecrets_and_code(
    CLIENT_SECRET_FILE,
    ['https://www.googleapis.com/auth/drive.appdata', 'profile', 'email'],
    auth_code)

# Call Google API
http_auth = credentials.authorize(httplib2.Http())
drive_service = discovery.build('drive', 'v3', http=http_auth)
appfolder = drive_service.files().get(fileId='appfolder').execute()

# Get profile info from ID token
userid = credentials.id_token['sub']
email = credentials.id_token['email']