The "message/http" content-type is typically only seen in the response body content to a TRACE method (which is unsupported by Jetty for security reasons).
Host: www.company.com
Connection: Close
(blank line)
HTTP/1.1 200 OK
Transfer-Encoding: chunked
Date: Wed, 15 Feb 2017 09:44:21 GMT
Content-Type: message/http
Connection: close
Server: ImpressiveServer/1.2.3.4 (Unix) Connection: close
Via: 1.1 bogusproxy
9d
TRACE / HTTP/1.1
Connection: keep-alive
Via: 1.1 bogusproxy
X-Foo: Value1,
Value2,
Value3
X-Forwarded-For: 111.69.185.59, 111.69.5.234
0
It was removed from the spec specifically because it causes security issues. (header injection)
Note: Internet Explorer, Chrome, Firefox, and most proxies do not support header folding anymore.
What are you trying to do is going to be increasingly more difficult as time goes on (not only will Jetty reject it, but so must http proxies and the like)
Historically, HTTP header field values could be extended over
multiple lines by preceding each extra line with at least one space
or horizontal tab (obs-fold). This specification deprecates such
line folding except within the message/http media type
(Section 8.3.1). A sender MUST NOT generate a message that includes
line folding (i.e., that has any field-value that contains a match to
the obs-fold rule) unless the message is intended for packaging
within the message/http media type.
Your clients MUST NOT send folded http headers.
It is highly unlikely that Jetty will reintroduce header folding.
You'll have to make a very good (security minded) case for it.
