这就是我设法让它与Google Apps域协同工作的方式：

This is how I managed to get it work with a Google Apps domain:

1.-使用谷歌应用用户打开 开发者控制台

1.- Using a google apps user open the developer console

2.-创建一个新的项目（即 MyProject ）

2.- Create a new project (ie MyProject)

3。 - 转到[Apis& auth]> [凭据]并创建新的 [服务帐户] 客户ID

3.- Go to [Apis & auth] > [Credentials] and create a new [Service Account] client ID

4.-复制[服务帐户]的[客户ID]（如xxx.apps.googleusercontent.com之类）供以后使用

4.- Copy the [service account]'s [Client ID] (the one like xxx.apps.googleusercontent.com) for later use

5.-现在您必须 删除域名范围内的服务帐户权限 ，以便授权您的appl代表Google Apps中的用户访问用户数据域名
...请转到 google apps域管理控制台

5.- Now you have to Delegate domain-wide authority to the service account in order to authorize your appl to access user data on behalf of users in the Google Apps domain ... so go to your google apps domain admin console

6.-转到[安全]部分找到[高级设置] （它可能是隐藏的，所以你必须点击[显示更多..]）

6.- Go to the [Security] section and find the [Advanced Settings] (it might be hidden so you'd have to click [Show more..])

7.-点击con [管理API客户端访问]

7.- Click con [Manage API Client Access]

8.-粘贴[客户端]您之前在[4]中复制到[客户名称]文本框中的ID]。

8.- Paste the [Client ID] you previously copied at [4] into the [Client Name] text box.

9.-要将您的应用完全访问权限授予gmail，请在[API范围]文本框中输入： https://mail.google.com ， https：// www.googleapis.com/auth/gmail.compose ， https://www.googleapis.com/auth/ gmail.modify ， https://www.googleapis.com/auth/gmail.readonly
（输入所有范围非常重要）

9.- To grant your app full access to gmail, at the [API Scopes] text box enter: https://mail.google.com, https://www.googleapis.com/auth/gmail.compose, https://www.googleapis.com/auth/gmail.modify, https://www.googleapis.com/auth/gmail.readonly (it's very important that you enter ALL the scopes)

现在你'已完成所有设置...现在代码：

Now you've done all the settings... now the code:

1.-创建一个HttpTransport

1.- Create an HttpTransport

private static HttpTransport _createHttpTransport() throws GeneralSecurityException,
                                                           IOException { 
    HttpTransport httpTransport = new NetHttpTransport.Builder()                                                 
                                                      .trustCertificates(GoogleUtils.getCertificateTrustStore())
                          .build();
    return httpTransport;
}

2.-创建一个JSonFactory

2.- Create a JSonFactory

private static JsonFactory _createJsonFactory() {
    JsonFactory jsonFactory = new JacksonFactory();
    return jsonFactory;
}

3.-创建Google凭证

3.- Create a google credential

private static GoogleCredential _createCredentialUsingServerToken(final HttpTransport httpTransport,
                                                                  final JsonFactory jsonFactory) throws IOException,
                                                                                                        GeneralSecurityException {
    // Use the client ID when making the OAuth 2.0 access token request (see Google's OAuth 2.0 Service Account documentation).
    String serviceAccountClientID = "327116756300-thcjqf1mvrn0geefnu6ef3pe2sm61i2q.apps.googleusercontent.com"; 

    // Use the email address when granting the service account access to supported Google APIs 
    String serviceAccountUserEmail = "xxxx@developer.gserviceaccount.com";

    GoogleCredential credential = new GoogleCredential.Builder()
                                                .setTransport(httpTransport)
                                                .setJsonFactory(jsonFactory)
                                                .setServiceAccountId(serviceAccountUserEmail)    // requesting the token
                                                .setServiceAccountPrivateKeyFromP12File(new File(SERVER_P12_SECRET_PATH))
                                                .setServiceAccountScopes(SCOPES)    // see https://developers.google.com/gmail/api/auth/scopes
                                                .setServiceAccountUser("user@example.com")
                                                .build();    
    credential.refreshToken();
    return credential;
}

注意：在setServiceAccountUser（）方法中使用任何来自您的Google应用领域的用户

NOTE: At setServiceAccountUser() method use any user from your google apps domain

4.-创建Gmail服务

4.- Create a Gmail Service

private static Gmail _createGmailService(final HttpTransport httpTransport,
                                         final JsonFactory jsonFactory,
                                         final GoogleCredential credential) {
    Gmail gmailService = new Gmail.Builder(httpTransport,
                                            jsonFactory,
                                            credential)
                                   .setApplicationName(APP_NAME)
                                   .build();
    return gmailService;
}

现在，您可以使用GmailService执行任何操作，例如发送电子邮件; - ）如 https://developers.google.com/gmail/api/guides/sending 所述

Now you can do whatever you want with the GmailService like send an email ;-) as described at https://developers.google.com/gmail/api/guides/sending