FYI I've documented this at https://www.jvt.me/posts/2020/05/25/read-servlet-request-body-multiple/ based on https://stackoverflow.com/a/36619972/2257038 and https://stackoverflow.com/a/30748533/2257038 - this caches the actual ServletInputStream rather than just the bytes that are returned.
by 
Jamie Tanna
.