使用GAE服务帐户的Gmail Java API

我正在尝试使用GAE服务帐户阅读gmail消息。下面类似的代码可以很好地读取谷歌日历，但对于gmail来说失败了。我在域中只有一个用户（同时也是管理员帐户）。我正在尝试访问该用户的gmail）。任何关于我的代码失败原因的帮助都会很好

我已为以下范围授予了域范围的权限

Email (Read/Write/Send)  https://mail.google.com/ 
https://www.googleapis.com/auth/admin.directory.user.readonly
Calendar (Read-Write)  https://www.googleapis.com/auth/calendar 
https://www.googleapis.com/auth/drive 
https://www.googleapis.com/auth/userinfo.email 
https://www.googleapis.com/auth/userinfo.profile

我在谷歌应用程序引擎中启用了以下API：

Admin SDK
Calendar API
Drive API
Gmail API
Google Cloud SQL
Google Cloud Storage
Google Cloud Storage JSON API 

下面是创建gmail服务的代码：

    // Create HTTP transport
    HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();


    // Create JsonFactory using com.google.api.client.json.jackson2.JacksonFactory
    JsonFactory jsonFactory = new JacksonFactory();

    // Get service accont (contain service account email and P12 file name)
    BaseGoogleService.GoogleServiceAccount serviceAccount = getGoogleServiceAccount();

    //load private key from class path to File object.
    Resource resource = appContext.getResource("classpath:"+serviceAccount.getServiceAccountPrivateKeyFile());
    File privateKeyFile = resource.getFile();

    // Create Google credential for service account
    List<String> accountScopes = new ArrayList<String>();
    accountScopes.add(GmailScopes.MAIL_GOOGLE_COM);
    Credential credential = new GoogleCredential.Builder()
            .setTransport(httpTransport)
            .setJsonFactory(jsonFactory)
            .setServiceAccountId(serviceAccount.getServiceAccountId())
            .setServiceAccountScopes(accountScopes)
            .setServiceAccountPrivateKeyFromP12File(privateKeyFile)
            .build();

    // Create Gmail client

    Gmail gmailClient = new Gmail.Builder(httpTransport, jsonFactory, credential)
    .build();

当我执行这段代码时，我得到了下面的错误

com.google.api.client.googleapis.json.GoogleJsonResponseException: 500 OK
{
  "code" : 500,
  "errors" : [ {
   "domain" : "global",
   "message" : "Backend Error",
   "reason" : "backendError"
  } ],
  "message" : "Backend Error"
}
at com.google.api.client.googleapis.json.GoogleJsonResponseException.from(GoogleJsonResponseException.java:145)
at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:113)
at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:40)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest$1.interceptResponse(AbstractGoogleClientRequest.java:312)
at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1049)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:410)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:343)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:460)

---

我能让它工作

两件事：

在构建GoogleCredential时必须添加。userEmail表示要模拟的电子邮件id

对于管理员帐户，无法执行此操作。我不得不向域名中添加一个用户并访问该用户的gmail

---

我得到了它。两件事：1。在构建GoogleCredential时必须添加“.setServiceAccountUser（userEmail）”。2.对于管理员帐户，无法执行此操作。我不得不向域名中添加一个用户并访问该用户的gmail。

com.google.api.client.googleapis.json.GoogleJsonResponseException: 500 OK
{
  "code" : 500,
  "errors" : [ {
   "domain" : "global",
   "message" : "Backend Error",
   "reason" : "backendError"
  } ],
  "message" : "Backend Error"
}
at com.google.api.client.googleapis.json.GoogleJsonResponseException.from(GoogleJsonResponseException.java:145)
at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:113)
at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:40)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest$1.interceptResponse(AbstractGoogleClientRequest.java:312)
at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1049)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:410)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:343)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:460)