java.io.IOException：获取服务帐户的访问令牌时出错：401 gmail api

Question

java.io.IOException: Error getting access token for service account: 401 Unauthorized
    at com.google.auth.oauth2.ServiceAccountCredentials.refreshAccessToken(ServiceAccountCredentials.java:444)
    at com.google.auth.oauth2.OAuth2Credentials.refresh(OAuth2Credentials.java:157)
    at com.google.auth.oauth2.OAuth2Credentials.getRequestMetadata(OAuth2Credentials.java:145)
    at com.google.auth.oauth2.ServiceAccountCredentials.getRequestMetadata(ServiceAccountCredentials.java:603)
    at com.google.auth.http.HttpCredentialsAdapter.initialize(HttpCredentialsAdapter.java:91)
    at com.google.api.client.http.HttpRequestFactory.buildRequest(HttpRequestFactory.java:88)
    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.buildHttpRequest(AbstractGoogleClientRequest.java:430)
    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:549)
    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:482)
    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:599)
    at com.soo.gsuite.GmailQuickstart.sendMessage(GmailQuickstart.java:168)
    at com.soo.gsuite.GmailQuickstart.main(GmailQuickstart.java:275)
Caused by: com.google.api.client.http.HttpResponseException: 401 Unauthorized
    at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1094)
    at com.google.auth.oauth2.ServiceAccountCredentials.refreshAccessToken(ServiceAccountCredentials.java:441)
    ... 11 more

代码如下：

public static void main(String... args) throws IOException, GeneralSecurityException {
    // Build a new authorized API client service.
    final NetHttpTransport HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();
    try {
        Gmail service = gmsEmailServiceAccount("yanhen@benexxxackaging.com");
        // Directory service2 = getDirectoryService("admin@benexxxackaging.com");
        MimeMessage emailContent = createEmail("admin@benexxxackaging.com", "me", "test", "test");
        sendMessage(service, "admin@benexxxackaging.com", emailContent);
        sendMessage(service, "admin@benexxxackaging.com", emailContent);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
public static Gmail gmsEmailServiceAccount(String userEmail)
        throws GeneralSecurityException, IOException, URISyntaxException {
    /*
     * InputStream resourceAsStream = new
     * GmailQuickstart().getClass().getClassLoader()
     * .getResourceAsStream(getJsonDataFromPath(userEmail));
     */
    InputStream resourceAsStream = GmailQuickstart.class.getResourceAsStream(CREDENTIALS_FILE_PATH);

    OAuth2Credentials credential = ServiceAccountCredentials.fromStream(resourceAsStream).createDelegated(userEmail)
            .createScoped(GMSGmailScopesOnly());
    HttpCredentialsAdapter adapter = new HttpCredentialsAdapter(credential);
    Gmail service = new Gmail.Builder(new NetHttpTransport(), JSON_FACTORY, adapter)
            .setApplicationName("Gmail API Java Quickstart").build();
    return service;
}

private static MimeMessage createEmail(String to, String from, String subject, String bodyText)
        throws MessagingException {
    Properties props = new Properties();
    Session session = Session.getDefaultInstance(props, null);

    MimeMessage email = new MimeMessage(session);
    email.setFrom(new InternetAddress(from));
    email.addRecipient(javax.mail.Message.RecipientType.TO, new InternetAddress(to));
    email.setSubject(subject);
    email.setText(bodyText);
    return email;
}

public static void sendMessage(Gmail service, String userId, MimeMessage email)
        throws MessagingException, IOException {
    Message message = createMessageWithEmail(email);
    message = service.users().messages().send(userId, message).execute();

    System.out.println("Message id: " + message.getId());
    System.out.println(message.toPrettyString());
}