ExtJs——TreePanel(动态)！！！

Ext.onReady(function(){
var root = new Ext.tree.AsyncTreeNode({id:'1',text:'根节点',leaf:false});
var tree = new Ext.tree.TreePanel({
dataUrl:'TreeServlet.do',
title:'异步加载节点',
width:300,
height:300
});
tree.setRootNode(root);
tree.render(Ext.getBody());
});

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=utf-8");
PrintWriter out = resp.getWriter();
String id = req.getParameter("node");
if (id != null) {
if ("1".equals(id)) {
out
.println("[{id:'2',text:'层级_1',leaf:false},{id:'3',text:'层级_2',leaf:true}]");
} else if ("2".equals(id)) {
out
.println("[{id:'4',text:'层级_1_1',leaf:false},{id:'5',text:'层级_1_2',leaf:true}]");
} else if ("4".equals(id)) {
out
.println("[{id:'6',text:'层级_1_1_1',leaf:false},{id:'7',text:'层级_1_1_2',leaf:true}]");
} else if ("6".equals(id)) {
out
.println("[{id:'8',text:'层级_1_1_1_1',leaf:true},{id:'9',text:'层级_1_1_1_2',leaf:true}]");
}
out.flush();
out.close();
}
}