title: Using url-expression
body: <p>I have a spring integration configured to build a url from a property and some variables:</p>
  
  <pre><code>    &lt;int-http:outbound-gateway
              url="${pdf.url}?id={id}&amp;amp;version={version}"
              request-factory="int.http.requestFactory"
              http-method="GET"
              transfer-cookies="false"
              header-mapper="fTokenHeaderMapper"
              expected-response-type="java.lang.String" &gt;
          &lt;int-http:uri-variable name="id" expression="payload.id"/&gt;
          &lt;int-http:uri-variable name="version" expression="payload.version"/&gt;
      &lt;/int-http:outbound-gateway&gt;
  </code></pre>
  
  <p>Now I want to change it so that the server part (pdf.url) could be changed on the fly and not only on startup. To achieve that I have changed from 'url' to 'url-expression' and something like this:</p>
  
  <pre><code>    &lt;int-http:outbound-gateway
              url-expression="@configurationService.getConfiguration('pdf.url')?id={id}&amp;amp;version={version}"
              request-factory="int.http.requestFactory"
              http-method="GET"
              transfer-cookies="false"
              header-mapper="fTokenHeaderMapper"
              expected-response-type="java.lang.String" &gt;
          &lt;int-http:uri-variable name="id" expression="payload.id"/&gt;
          &lt;int-http:uri-variable name="version" expression="payload.version"/&gt;
      &lt;/int-http:outbound-gateway&gt;
  </code></pre>
  
  <p>This line seems to work:</p>
  
  <pre><code>url-expression="@configurationService.getConfiguration('pdf.url')"
  </code></pre>
  
  <p>But how do I include the variables in a similar way as the first example?</p>