title: How to enrich the message headers with uri variables or parameters in Spring Integration java dsl
body: <p>I'm trying to enrich the headers of the messages coming from an http inbound gateway ;
  my uri looks like this: </p>
  
  <pre><code>requestMapping.setPathPatterns("/context/{fooId}");
  </code></pre>
  
  <p>But I don't know how to use the setHeaderExpressions method of the HttpRequestHandlingMessagingGateway to catch the uri variable and put its value in the header.</p>
  
  <p>I have no more success with the .enrichHeaders(...) since this code generates an exception: </p>
  
  <pre><code>IntegrationFlows.from(requestNotificationChannel())
    .enrichHeaders(h -&gt; h.header("fooId", "#pathVariables.fooId")
  </code></pre>
  
  <p>What is the good way to extract the values from the uri-variables and/or from the parameters ?</p>
  
  <p>Thanks !</p>