You want to enhance a default handler, fix a bug or just use an other jquery plugin as the default in Struts2 jQuery Plugin? Here is a short example hot to overwrite the handler function for the autocompleter in Struts2 jQuery Plugin.
  <sj:head />
  <script type="text/javascript">
  $.struts2_jquery.autocompleter = function($elem, options) {
	alert("my own autocompleter handler for "+options.id);
  };
  </script>