如何运行从Java Servlet部署为网络应用程序的Google Apps脚本？

Question

我创建了GAS并将其部署为Google Web应用程序。 可以通过https://script.google.com/macros/s/..../exec URL访问。 现在，我想从Java servlet运行它。 我在console.developers.google.com中创建了应用程序，为服务帐户创建了CLIENT ID ，并创建了API KEY和私钥文件 。

现在，我尝试如下运行脚本：

    HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
    JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
    // Build service account credential.
    GoogleCredential credential = new GoogleCredential.Builder().setTransport(httpTransport)
        .setJsonFactory(jsonFactory)
        .setServiceAccountId("...@developer.gserviceaccount.com")
        .setServiceAccountScopes(Collections.singleton("https://script.google.com"))
        .setServiceAccountPrivateKeyFromP12File(new File(getClass().getClassLoader().getResource("key/eForms-055a7029cd36.p12").toURI()).getAbsoluteFile())
        .build();

            // Set up and execute a Google Cloud Storage request.
    String URI = "https://script.google.com/macros/s/.../exec?payload="+form.toString();
    HttpRequestFactory requestFactory = httpTransport.createRequestFactory(credential);
    GenericUrl url = new GenericUrl(URI);
    HttpRequest http_request = requestFactory.buildGetRequest(url);
    HttpResponse response = http_request.execute();
    String content = response.parseAsString();

我得到

com.google.api.client.auth.oauth2.TokenResponseException: 400 Bad Request
{
  "error" : "invalid_grant"
}

我认为我设置了错误的插槽，但是要设置哪个？