Issue #2222 "100-Continue is not correctly responded for chunked requ…

[carryel]

…ests" (#2222)

Chunked Transfer Coding supports 100-continue.

• In case of chunked transfer coding, "Expect: 100-continue" is processed immediately after HttpHeader is parsed.
• Added tests for chunked transfer encoding to HttpContinueTest.
• All tests passed.

PS) However, custom sendAcknowledgment() of HttpHandler cannot be supported in that situation.

[carryel]

https://datatracker.ietf.org/doc/html/rfc7231#section-5.1.1 explains it as follows:

 A 100-continue expectation informs recipients that the client is
   about to send a (presumably large) message body in this request and
   wishes to receive a 100 (Continue) interim response if the
   request-line and header fields are not sufficient to cause an
   immediate success, redirect, or error response.

Examples include:

     PUT /somewhere/fun HTTP/1.1
     Host: origin.example.com
     Content-Type: video/h264
     Content-Length: 1234567890987
     Expect: 100-continue

Grizzly handles 100-continue well for HTTP headers with Content-Length, but it does not consider cases where the body has chunk-size, such as chunked transfer coding.

I think the chunked transfer coding spec for 100-continue is a little unclear.
For chunked transfer coding, Grizzly tries to parse up to the chunk-size in the body and passes the control to the HttpHandler. However, in the case of 100-continue, it is determined when only the header is transmitted without the body.

Therefore, in the case of chunked transfer coding, we added the ability to process 100-continue immediately after header parsing is finished.
In other cases, after header parsing, control is passed to HttpHandler as before, and 100-continue is determined therein.
In the case of chunked transfer coding, 100-continue is processed before control is given to HttpHandler, so the existing custom HttpHandler#sendAcknowledgment() in Grizzly cannot be processed. I thought this was the best we could do given the current unclear specs and Grizzly implementation.