高手帮我看看

这是显示页面
<%@ page language="java" pageEncoding="GBK" contentType="text/html; charset=GBK"%>
<%@ taglib uri="http://jakarta.apache.org/struts/tags-bean" prefix="bean"%> 
<%@ taglib uri="http://jakarta.apache.org/struts/tags-html" prefix="html"%>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>
<jsp:useBean id="list" scope="request" class="com.kzon.DB.web_menuDao"></jsp:useBean>
<bean:define id="List" name="list" property="parentname"></bean:define> 
<html> 
<head>
<title>JSP for RootForm form</title>
</head>
<body>
<table border="1">
     <tr>
     <th>根目录</th>
     </tr>
    <logic:iterate id="root" name="List">
    <tr>
     <td><bean:write name="root" property="name"/></td>
     </tr>
     </logic:iterate>
    </table>
<html:form action="/root">
<html:submit/><html:cancel/>
</html:form>
</body>
</html>
这是ACTION里代码
/*
 * Generated by MyEclipse Struts
 * Template path: templates/java/JavaClass.vtl
 */
package com.yourcompany.struts.action;import java.util.ArrayList;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;import com.kzon.DB.web_menuDao;
import com.kzon.DB.web_menuVo;
import com.yourcompany.struts.form.RootForm;/** 
 * MyEclipse Struts
 * Creation date: 05-08-2007
 * 
 * XDoclet definition:
 * @struts.action path="/root" name="rootForm" input="/form/root.jsp" scope="request" validate="true"
 */
public class RootAction extends Action {
/*
 * Generated Methods
 */ /** 
 * Method execute
 * @param mapping
 * @param form
 * @param request
 * @param response
 * @return ActionForward
 */
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
RootForm rootForm = (RootForm) form;
web_menuDao menudao=new web_menuDao();
ArrayList list=new ArrayList();
list=menudao.getParentname();
request.setAttribute("list", list);
return mapping.findForward("suc");
}
}
启动应用服务器后，打开页面报的错
 The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Exception thrown by getter for property parentname of bean list
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:375)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause javax.servlet.ServletException: Exception thrown by getter for property parentname of bean list
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:858)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791)
org.apache.jsp.form.root_jsp._jspService(root_jsp.java:160)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause javax.servlet.jsp.JspException: Exception thrown by getter for property parentname of bean list
org.apache.struts.taglib.TagUtils.lookup(TagUtils.java:968)
org.apache.struts.taglib.bean.DefineTag.doEndTag(DefineTag.java:230)
org.apache.jsp.form.root_jsp._jspService(root_jsp.java:90)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)