title: how to check query params are null or empty in apache camel
body: <p>I am trying to use camel-restlet-2.14.0 to call an external REST service. The call to the rest service will depends on the query parameters passed by the user.i am trying to do this using the xml configuration.</p>
  
  <pre><code>&lt;spring:camelContext trace="true"&gt;
          &lt;spring:route id="countries-fetch-route"&gt;
              &lt;spring:from uri="restlet:/verifyTest?restletMethod=GET"&gt;
              &lt;/spring:from&gt;
              &lt;spring:choice&gt;
                  &lt;spring:when&gt;
                      &lt;spring:simple&gt;{header.abc} != null &amp;amp;&amp;amp; {header.pqr} != null&lt;/spring:simple&gt;     
                      &lt;spring:to uri="restlet:http://localhost:10080/TestRESTfulService/api/v1/av/verify/abc?abc={header.abc}&amp;amp;pqr={header.pqr}"&gt;&lt;/spring:to&gt;
                  &lt;/spring:when&gt;
              &lt;/spring:choice&gt;
             &lt;spring:transform&gt;
                  &lt;spring:simple&gt;${body}&lt;/spring:simple&gt;
              &lt;/spring:transform&gt;
          &lt;/spring:route&gt;
      &lt;/spring:camelContext&gt;
  </code></pre>
  
  <p>if anybody can help me to check the headers(query Params) that would be really helpful</p>