http://struts.jgeppert.com/struts2-jquery-showcase/index.action
Check out the More widgets
-> Tree
part
use the onClickTopics
to catch the click event
Example
<sjt:tree
id="jsonTree"
href="%{treeDataUrl}"
onClickTopics="treeClicked"
/>
And you can get which element is clicked in the listen topic
$.subscribe('treeClicked', function(event, data) {
var item = event.originalEvent.data.rslt.obj;
alert('Clicked ID : ' + item.attr("id") + ' - Text ' + item.text());
});