Just mocked this up based on your descriptions.
A Jetty server using Jetty 9.2.13.v20150730
A servlet on "/mock/*" that has a doGet() and doPost() enabled.
Had the implementation of this servlet just respond what it got.
Using curl to access said servlet.
* About to connect() to 127.0.0.1 port 2013 (#0)
* Trying 127.0.0.1...
* Adding handle: conn: 0x11588d0
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x11588d0) send_pipe: 1, recv_pipe: 0
* Connected to 127.0.0.1 (127.0.0.1) port 2013 (#0)
> User-Agent: curl/7.32.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Date: Wed, 12 Aug 2015 21:32:07 GMT
< Content-Type: text/plain; charset=ISO-8859-1
< Content-Length: 62
* Server Jetty(9.2.13.v20150730) is not blacklisted
< Server: Jetty(9.2.13.v20150730)
<
* Connection #0 to host 127.0.0.1 left intact
$
* About to connect() to 127.0.0.1 port 2013 (#0)
* Trying 127.0.0.1...
* Adding handle: conn: 0x12da920
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x12da920) send_pipe: 1, recv_pipe: 0
* Connected to 127.0.0.1 (127.0.0.1) port 2013 (#0)
> User-Agent: curl/7.32.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 1103791
> Expect: 100-continue
>
< HTTP/1.1 200 OK
< Date: Wed, 12 Aug 2015 21:32:53 GMT
< Content-Type: text/plain; charset=ISO-8859-1
< Content-Length: 63
< Connection: close
* Server Jetty(9.2.z-SNAPSHOT) is not blacklisted
< Server: Jetty(9.2.z-SNAPSHOT)
<
* Closing connection 0
Can you use "-vv" on your curl line too?