title: Spring Integration combine path variables and post body in payload expression
body: <p>Using an http inbound-gateway I am able to specify a payload-expression using SPEL that will access header, requestParams, and pathVariables.  How do I also include the body from a POST?  An example of what I currently have is</p>
  
  <pre><code>&lt;int-http:inbound-gateway path="/document/{product}/{id}/blah"
                            supported-methods="GET"
                            request-channel="documentService.blah"
                            reply-channel="httpReplyChannel"
                            message-converters="jsonMessageConverter"
                            header-mapper="defaultHttpHeaderMapper"
                            payload-expression="new RequestDTO(
                                                   #pathVariables.product,
                                                   #pathVariables.id,
                                                   #requestParams['optionalParam'],
                                                   headers.get('headerKey')) /&gt;
  </code></pre>
  
  <p>That works fine, however I want to add an additional parameter to the RequestDTO constructor that is the actual post body (obviously I will change the method) and have it serialized into the appropriate type.</p>
  
  <p>Is this possible?  Thanks in advance.</p>