title: spring-integration: how to pass post request parameters to http-outbound
body: <p>I need to pass a  post request parameters to an int-http:outbound-gateway and can't find any simple way to do this. What I have to do is issue a http request to a couch db fetching multiple documents with a single request as described in the couch db documentation:</p>
  
  <pre><code>curl -d '{"keys":["bar","baz"]}' -X POST http://127.0.0.1:5984/foo/_all_docs?include_docs=true
  </code></pre>
  
  <p>So how do I pass the param with the name 'keys' to the int-http:outbound-gateway? (I have all  the data I need in the payload of the message)</p>
  
  <pre><code>&lt;int-http:outbound-gateway request-channel="requestChannel" 
                       url="http://127.0.0.1:5984/foo/_all_docs?include_docs=true" 
                       http-method="POST"
                       expected-response-type="java.lang.String"/&gt;
  </code></pre>