how to add the css effect on struts2 jquery tree

Question

I'm having problem with my jquery tree view. now I'm using this : http://struts.jgeppert.com/struts2-jquery-showcase/index.action

I want to make the css background on selected tree node after the node is clicked. How should I do, pls give me some idea? The css effect displays when handover on tree node but, after clicked, the css effect does not show.

I added this <sj:head jqueryui="true" jquerytheme="showcase" /> in head tag

, added the following code in script

$(function(){
        $.subscribe('treeClicked', function (event, data){
            alert("treeClicked");// check if script called on page load
            //Get the next item, this is the tree node object is selected, many operations need it
            var item = event.originalEvent.data.rslt.obj;
            //For example, we want to select the node id suggest, you can write like this
            alert ('Clicked ID : ' + item.attr ("id"));
            document.getElementById("g_selected_uid").value = item.attr("id");
            document.forms.selectedUnitForm.submit();
            //self.close();
        });
    });

and then here is my jquery tree code -

<sjt:tree id="treeDynamicAjax"
jstreetheme="apple"
rootNode="#session.UNT_LIST"
childCollectionProperty="children"
nodeTitleProperty="title"
nodeIdProperty="id"
openAllOnLoad="true"
onClickTopics="treeClicked"
></sjt:tree>