controller_ajax.groovy

def analyze = {
 render "Content"
}

gsp_ajax_example.jsp

<div id="ajax_form">
  <g:remoteLink action="analyze"
          update="[success:'ajax_data',failure:'error']">Ajax Action</g:remoteLink>
</div>

<!-- Spinner Trick-->
<div id='spinner' class='spinner' style='display:none;'>
  <img src='${createLinkTo(dir: 'images', file: 'spinner.gif')}' alt="Loading..." title="Loading..."/><p><g:message code="Идет загрузка.."/></p>
</div>

<div id="ajax_data">

gsp_ajax_js_example.jsp

<g:javascript src="jquery/jquery.js" />

<g:javascript>
  $(document).ready(function() {

    $("#spinner").bind("ajaxSend", function() {
      $(this).fadeIn();
    }).bind("ajaxComplete", function() {
      $(this).fadeOut();
    })
  });
</g:javascript>