关于Struts验证的问题

UploadAction中的代码是这样的
/*
 * Generated by MyEclipse Struts
 * Template path: templates/java/JavaClass.vtl
 */
package com.ph.struts.action;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 org.apache.struts.action.ActionMessage;
import org.apache.struts.upload.FormFile;
import java.io.*;import com.ph.struts.form.UploadForm;/** 
 * MyEclipse Struts
 * Creation date: 03-27-2011
 * 
 * XDoclet definition:
 * @struts.action path="/upload" name="uploadForm" input="/upload.jsp" scope="request" validate="true"
 * @struts.action-forward name="success" path="/index.jsp"
 */
public class UploadAction 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) {
UploadForm ufo = (UploadForm) form;// TODO Auto-generated method stub
try {
String name = ufo.getName();
if(name.equals("abc")){
request.setAttribute("nameexists", new ActionMessage("message.name.exists",name));
return mapping.getInputForward();
}
} catch (Exception e) {
e.printStackTrace();
}

return mapping.findForward("success");
}
}upload.jsp 中的代码是这样的
<%@ page language="java" pageEncoding="gbk"%>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%> 
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%>
 
<html> 
<head>
<title>JSP for UploadForm form</title>
</head>
<body>
<html:form action="/upload" enctype="multipart/form-data">
name : <html:text property="name"/><bean:message name="nameexists"/>
<html:errors property="name"/><br/>
age:<html:text property="age"/><html:errors property="age"/><br>
photo : <html:file property="file"/><html:errors property="file"/><br/>
<html:submit/><html:cancel/>
</html:form>
</body>
</html>
服务器报错是则样的
javax.servlet.jsp.JspException: Cannot find bean: "nameexists" in any scope
at org.apache.struts.taglib.TagUtils.lookup(TagUtils.java:935)
at org.apache.struts.taglib.bean.MessageTag.doStartTag(MessageTag.java:210)
at org.apache.jsp.upload_jsp._jspx_meth_bean_005fmessage_005f0(upload_jsp.java:190)
at org.apache.jsp.upload_jsp._jspx_meth_html_005fform_005f0(upload_jsp.java:122)
at org.apache.jsp.upload_jsp._jspService(upload_jsp.java:85)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)请高手们指点，谢了