访问令牌和刷新令牌在Google服务帐户中的驱动器api中为空

Question

我在运行我的代码时将访问令牌和刷新令牌设为null。没有编译错误。我不明白为什么会发生这种情况。 plz帮助。

我正在从官方网站提供的示例中查看此示例。

其实，我想做服务器到服务器授权，可以使用服务帐户在谷歌驱动器完成。我甚至不想向用户显示同意屏幕。我下面谷歌驱动器文档，这是在

https://developers.google.com/identity/protocols/OAuth2ServiceAccount

我的代码是：

public class TFT { 

private static final String ApplicationName = "Boston"; 
private static final String serviceAccountEmailAddress = "[email protected]"; 
private static final String serviceAccountUser = "[email protected]"; 

private static List<File> retrieveAllFiles(Drive service) throws IOException { 
    List<File> result = new ArrayList<>(); 
    Files.List request = service.files().list(); 

    do { 
     FileList files = request.execute(); 

     result.addAll(files.getFiles()); 

     request.setPageToken(files.getNextPageToken()); 

    } while (request.getPageToken() != null && request.getPageToken().length() > 0); 
    return result; 
} 

public static Drive getDriveService() throws IOException { 

    HttpTransport httpTransport = new NetHttpTransport(); 
    JacksonFactory jsonFactory = new JacksonFactory(); 

    GoogleCredential credential = null; 

    try { 
     credential = new GoogleCredential.Builder() 
       .setTransport(httpTransport) 
       .setJsonFactory(jsonFactory) 
       .setServiceAccountId(serviceAccountEmailAddress) 
       .setServiceAccountScopes(DriveScopes.all()) 
       .setServiceAccountUser(serviceAccountUser) 
       .setServiceAccountPrivateKeyFromP12File(new java.io.File("/home/xpointers/Downloads/Boston-2b55ddf4a5c8.p12")) 
       .build(); 

    } catch (GeneralSecurityException | IOException e) { 
     e.printStackTrace(); 
    } 

    Drive service = new Drive.Builder(httpTransport, jsonFactory, credential).setApplicationName(ApplicationName) 
      .build(); 
    return service; 
} 

private java.io.File getp12File(String fileName) { 


    ClassLoader classLoader = getClass().getClassLoader(); 
    return new java.io.File(classLoader.getResource(fileName).getFile()); 

} 

public static void main(String[] args) { 

    try { 

     Drive service = getDriveService(); 

     List<File> files; 

     files = retrieveAllFiles(service); 

     System.out.println(files); 

    } catch (IOException e) { 
     e.printStackTrace(); 
    } 

} 

}

Answer 1

你可以参考这个thread这表明使用credential.refreshToken();。

我们需要调用credential.refreshToken();
然后
String token=credential.getAccessToken();

参考文献：

• How to get access token from GoogleCredential?
• OAuth2.0 : getaccessToken() returns NULL- - credential.refreshToken(); returns TRUE