JSP实现树形目录

<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<%@ page import="com.conn" %>
<%
conn conn=new conn();
ResultSet rs_superType=conn.executeQuery("select ID,superType from V_Type group by ID,superType order by superType desc");%>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<table width="100%"  border="0" cellspacing="0" cellpadding="0">
            <tr>
              <td><img src="images/shop_20.gif" width="201" height="80"></td>
            </tr>
            <tr>
              <td height="90" valign="top"><table width="100%" height="40"  border="0" cellpadding="0" cellspacing="0">
             <%
int ID_superType=0;
String superType="";
int m=1;
                        while(rs_superType.next()){
  ID_superType=rs_superType.getInt(1);
  superType=rs_superType.getString(2);
String sql="select * from V_Type where ID='"+ID_superType+"'";
ResultSet rs_subType=conn.executeQuery(sql);
String subType="";
int subID=0;
//获取记录总数
rs_subType.last();
int subType_RC=rs_subType.getRow();
rs_subType.first();
 %>
            <tr>
<td>
<%
                                        
if(subType_RC<=0){
%>
&nbsp;&nbsp;&nbsp;&nbsp;<img src="images/jian_null.gif" width="38" height="16" border="0">
<%=superType%>
<%
}else{
%>
&nbsp;&nbsp;&nbsp;&nbsp;<a href="Javascript:ShowTR(img<%=m%>,OpenRep<%=m%>)"><img src="images/jia.gif" border="0" alt="展开" id="img<%=m%>"></a>
<a href="Javascript:ShowTR(img<%=m%>,OpenRep<%=m%>)"><%=superType%></a>
<%
}
%>
                </td>
<%if (subType_RC>0){%>
  <tr id="OpenRep<%=m%>" style="display:none;">
   <td colspan="6">
<%do{
subType=rs_subType.getString(3);
subID=rs_subType.getInt(4);
%>
     <table width="100%"  border="0" cellspacing="-2" cellpadding="-2">
                   <tr>
                      <td height="25" align="center"><table width="90%"  border="0" cellspacing="0" cellpadding="0">
                  <tr onMouseOver="this.style.background='#EEEEEE'" onMouseOut="this.style.background=''">
                    <td width="15%">&nbsp;</td>
                    <td width="10%" align="center"><img src="images/folder.gif" width="16" height="16" border="0"> </td>
                    <td width="75%"><a href="type.jsp?Type=<%=subID%>"><%=subType%></a></td>
                  </tr>
              </table></td>
                   </tr>
                 </table>
 <% m++;  //注意，该条语句一定不能少
}while(rs_subType.next());
%>
   </td>
   <%}%>
  </tr>
<script language="javascript">
ShowTR(img1,OpenRep1)  //设置第1个结点为展开状态
function ShowTR(objImg,objTr){
if(objTr.style.display == ""){
objTr.style.display = "none";
objImg.src = "images/jia.gif";
objImg.alt = "展开";
}else{
objTr.style.display = "";
objImg.src = "images/jian.gif";
objImg.alt = "折叠";
}
}
</script>
<% }%>
                                 商品大类信息可以实现，但是点击+，就会出现IMG1无定义，是怎么回事？？？？错误在哪里啊，请大虾帮帮忙！！！！！ 小类信息不能展开啊？？？？？