struts结合ajax简单应用

应用很简单，初次使用ajax。
实现在下拉框中选种一个号，则从数据库中查出这号对应的数量，显示在页面上
<%@ page language="java" pageEncoding="GBK"%>
<%@page isELIgnored="false"%>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>
<%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html:html locale="true">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=GBK">
      <title><bean:message key="hx.title"/></title>
  </head>
 
<script language="javascript">
//获取XMLHttpRequest对象
var XMLHttpReq;
var FLAG;     
    function createXMLHttpRequest() {
if(window.XMLHttpRequest) {
XMLHttpReq = new XMLHttpRequest();
}
else if (window.ActiveXObject) {
try {
XMLHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
XMLHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {alert("创建对象失败!");}
}
}
}

function sendRequest(url) {
createXMLHttpRequest();
XMLHttpReq.open("post", url, true);
//XMLHttpReq.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
XMLHttpReq.onreadystatechange = processResponse;//指定processResponse()为响应函数
XMLHttpReq.send(null);
}
//processResponse()为响应函数
function processResponse() {
if (XMLHttpReq.readyState == 4) { 
    if (XMLHttpReq.status == 200) { 
if(FLAG ==12){//如果是12调用update();
update();
 }
}
    } function showInfo() {
FLAG=12;
var sbph=document.rkbForm.sbph.value;
alert(sbph);
if(document.rkbForm.sbph.value!=""){
sendRequest("../account/rkbajax.do?sbph="+sbph+"&flag="+FLAG);
}
}

function update(){
var shuliang=XMLHttpReq.responseXML.getElementsByTagName("shuliang");
document.form1.shuliang.value = shuliang[0].firstChild.data;
}
</script>
<link href="../css/style.css" type="text/css" rel="stylesheet">
<body>
<FONT face="宋体">
<table width="100%" height="26" border="1" align="center" cellpadding="0" cellspacing="0" bgColor="#CCCCCC">
<tr>
  <td width="100%"><bean:message key="init.title"/></td><td></td>
  </tr>
</table>
<TABLE id="Table1" style="Z-INDEX: 101; LEFT: 0px; POSITION: relative; TOP: -8px" cellSpacing="0"
borderColorDark="#ffffff" cellPadding="1" width="600" align="center" borderColorLight="#000000"
border="0">
  <tr>
    <td width="777">
<html:form action="/account/rkb.do" focus="sbph">
<table align="center" width="640" height="90" border="0">
<tr>
<td width="130" height="30" align="right"><bean:message key="hx.cprka9"/>：</td>
        <td colspan="8"><font color="red"><bean:message key="hx.cprka10"/></font></td>
</tr>
        <tr>
        <td width="130" height="30" align="right"><bean:message key="hx.cprka1"/>：</td>
        <td>
        <html:select property="sbph" name="rkbForm" onchange="showInfo()">//缺少对象错误
        <html:option value="">--选择申报批号--</html:option>
        <html:options collection="vlist" property="rsbph" labelProperty="rsbph"/>
        </html:select>
        </td>
        <td width="130" height="30" align="right"><bean:message key="hx.cprkb2"/>：</td>
        <td width="100"><html:text property="hxh" value=""/></td>
        <td width="130" height="30" align="right"><bean:message key="hx.cprkb3"/>：</td>
        <td width="100"><html:text property="zhonglei" value=""/></td>
      </tr>
       <tr>
        <td height="30" align="right"><bean:message key="hx.cprkb4"/>：</td>
        <td><html:text property="guige" value=""/></td>
        <td height="30" align="right"><bean:message key="hx.cprkb5"/>：</td>
        <td><html:text property="rksl" value=""/></td>
        <td height="30" align="right"><bean:message key="hx.cprka5"/>：</td>
        <td>
        <html:select property="clfs" value="热处理">
        <html:option value="热处理"><bean:message key="hx.cprka7"/></html:option>
        <html:option value="熏蒸"><bean:message key="hx.cprka8"/></html:option>
        </html:select>
        </td>
      </tr>
      <tr>
        <td height="30" align="right"><bean:message key="hx.cprkb6"/>：</td>
        <td><html:text property="shuliang" name="shuliang" value=""/></td>
      </tr>
      <tr>
    <td align="right">  
    </td>
    <td align="right">
    <html:submit> 
      <bean:message key="init.submit"/>                   
      </html:submit>
    </td>
    <td align="right">  
    </td>
    <td align="right">
      <html:reset> 
      <bean:message key="init.reset"/>                   
      </html:reset>
    </td>
  </tr>
    </table>
</html:form></td>
  </tr>
</table>
</td>
  </tr>
</table>
</body>
</html:html>
//action中部分方法
response.setContentType("text/xml; charset=utf-8");
response.setHeader("Cache-Control", "no-cache");
out.println("<response>");
out.println("<shuliang>" + shuliang+ "</shuliang>");
out.println("</response>");
out.close();
//struts配置文件
<action
      attribute="rkbForm"
      input="/account/cprkb.jsp"
      name="rkbForm"
      parameter="flag"
      path="/account/rkbajax"
      scope="request"
      type="com.shen.struts.action.RkbajaxAction">
      <forward name="success" path="/account/cprkb.jsp" />
      <forward name="fail" path="/account/cprkb.jsp" />
    </action>现在出现的问题是在这行老师报缺少对象错误，请朋友帮忙看下。上面已经标出了哪行