Struts2 jsp 无法得到 ACTION 的属性值

我的页面：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page import="java.util.*,com.opensymphony.xwork2.util.*" %>
<%@ taglib prefix="s" uri="/struts-tags"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">    
<html>    
<head>    
<title>Destroydrop &raquo; Javascripts &raquo; Tree</title>    
<link rel="StyleSheet" href="css/dtree.css" type="text/css" />    
<script type="text/javascript" src="js/dtree.js"></script>    
</head>    
<body>    
 <div class="dtree">    <script type="text/javascript">    
<!--    
d = new dTree('d');    
<%   
ValueStack vs= (ValueStack)request.getAttribute("struts.valueStack"); 
String str =(String)vs.findValue("str");
String[] air=str.split("@");
for(int i=0;i<air.length;i++){ 
 //   System.out.println(i+"="+str[i]);
  
%>    
d.add(<%=air[i]%>); 
 
<%}%>    
document.write(d);    
//-->    
</script>    
</div>   </body>    action 如下：package com.sinosky.air.sysmgr.action;import java.util.Iterator;
import java.util.List;
import java.util.Map;import javax.servlet.http.HttpServletRequest;import org.apache.struts2.ServletActionContext;import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.Action;
import com.opensymphony.xwork2.ActionContext;
import com.sinosky.air.po.treeinfo;
import com.sinosky.air.sysmgr.bo.Inodeservice;public class nodeaction extends ActionSupport { private Inodeservice nodeservice;
    private treeinfo  tree;
    private String str;    
    
public Inodeservice getNodeservice() {
return nodeservice;
} public void setNodeservice(Inodeservice nodeservice) {
this.nodeservice = nodeservice;
}
public treeinfo getTree() {
return tree;
} public void setTree(treeinfo tree) {
this.tree = tree;
}
public String getStr() {
return str;
} public void setStr(String str) {
this.str = str;
} public String execute() throws Exception
{

 ActionContext ctx = ActionContext.getContext();        HttpServletRequest request = (HttpServletRequest)ctx.get(ServletActionContext.HTTP_REQUEST);


// treeinfo treeInfo = new treeinfo();    
//这里只是取得TreeInfo表中所有数据，你可以根据自己的应用来取值    
List<treeinfo> treeList = nodeservice.findTreeAll();    
/*****将取得的记录依次添加到StringBuffer中，然后返回str字符串************/    
StringBuffer sb = new StringBuffer();    
String strr = null;    
String parid = null;    
sb.append("0,-1,''@");    
for(Iterator iter = treeList.iterator();iter.hasNext();){    
treeinfo tree = (treeinfo)iter.next();    
  
strr = tree.getNodeid()+","+tree.getParentid()+",'"+tree.getCaption()+"',"+tree.getNodeurl()+",'"+tree.getTarget()+"'@";    
sb.append(strr);    
}  
  
setStr(sb.toString());
   
      
return SUCCESS;
} }