The route :
  from("direct:start")
  .setProperty(Exchange.CHARSET_NAME, constant("iso-8859-1"))
  .process(new Processor() {            
        @Override
        public void process(Exchange exchange) throws Exception {
          Message m = exchange.getOut();
          m.setBody(exchange.getIn().getBody());
          m.setHeader(Exchange.HTTP_METHOD, HttpMethods.POST);
          m.setHeader(Exchange.CONTENT_ENCODING, "gzip" );
          m.setHeader(Exchange.CONTENT_LENGTH, m.getBody(byte[].class).length );
          m.setHeader(HttpHeaders.CONTENT_TYPE, "application/xml");
          m.setHeader(Exchange.HTTP_CHARACTER_ENCODING, "iso-8859-1");
          m.setHeader(HttpHeaders.ACCEPT_ENCODING, "gzip, deflate");        
        }
    })
  .marshal().gzip()
  .to("http4://remote.com/path")
  .unmarshal().gzip();
What I am sending :
String body = "<?xmlversion=\"1.0\"encoding=\"ISO-8859-1\"?><theXml></theXml>";
producer.sendBody(body);
I am getting
HTTP operation failed invoking http://remote.com/path with statusCode: 411
What is missing/wrong with this route ?
EDIT
The correct route would be
  from("direct:start")
  .process(new Processor() {            
        @Override
        public void process(Exchange exchange) throws Exception {
          Message m = exchange.getOut();
          m.setBody(exchange.getIn().getBody());
          m.setHeader(Exchange.HTTP_METHOD, HttpMethods.POST);
          m.setHeader(Exchange.CONTENT_ENCODING, "gzip" );
          m.setHeader(Exchange.CONTENT_TYPE, "application/xml");        
        }
    })
  // http4 takes care of compressing/decompressing gzip
  .to("http4://remote.com/path")
But now I have another problem : the remote server does not handle "Transfer-Encoding: Chuncked" Which seems to be the default way camel-http4 does it. And i can't figure out how to turn Chunked off.
See next question How to turn off “Transfer-Encoding Chuncked” in Camel-http4?