I'm working on the next edition of Sams' Teach Yourself Java in 24 Hours. Java 9 has a new HTTP client package, jdk.incubator.http, that makes it a lot easier to GET and POST to web servers and other software that communicates over HTTP.
For a demo, I needed a simple server that could take POST requests and do something with them without requiring a user login. I was about to write one when I realized I already had. This blog takes comments submitted over POST.
When the book comes out, I'll be able to see from these comments that readers have reached Hour 22.