You need to write your own.
If you are only doing HTTP GETs, it's quite easy, because there is no body and all you need is a stateless deserializer that looks for "\r\n\r\n". Just clone the CrLfSerializer and change it to look for "\r\n\r\n" instead of "\r\n".
Or, you can use the CrLfSerializer to get each header, with the end being indicated by an empty String.
POSTs etc are a little more tricky because the deserializer needs to maintain state - am I decoding headers? or the body? Plus, the HTTP body can be complex - multi-part mime, content-length header etc, etc. Writing a fully compliant HTTP parser is fairly complex.
The current deserializers are all stateless. You could maintain state in a Map, keyed by the InputStream, but you'd need some mechanism to clean up the map if you receive a half-baked message any time.
It's not too bad if you know exactly how the client will construct the body - just wait until you get "\r\n\r\n" and you know you are done with the headers. But you will still need to know when the body has been fully received.
Hope that helps.
If you get something working, you might want to submit it to the extensions repository.
Gary P. Russell
Spring Integration Team
SpringSource, a division of VMware