View Return POST Body

What is the correct way to get the body of a HTTP POST when submitted by a 3rd party to a vaadin view. Typical of payment processors that post a JSON response.

I dont particularly want to have a custom servlet.

During a BeforeEnterEvent, if I get “getReader() has already been called for this request” when using VaadinServletRequest getHttpServletRequest getInputStream as the request has already been consumed.

Any thoughts/recommendations?

custom servlet, spring controller or any other method - Vaadin routes does not support POST

Seems like such a fundamental problem when integrating with third parties that would make sense. Thanks.