用JSP+JavaScript打造二级级联下拉菜单

JSP+JavaScript打造二级级联下拉菜单：

class(一级栏目信息）：classId(自动编号），className（栏目名称）, Nclass（二级栏目信息）, NclassId（自动编号），NclassName(栏目名称），parentId（一级栏目id，与class表中的classId关联）

<%@ page contentType=text/html; charset=GB2312 language=java errorPage=../error.jsp %>
<%@ include file=../conn.jsp%>
<%@ include file=../ds.jsp%>
<%@ taglib uri=http://java.sun.com/jsp/jstl/sql divfix=sql %>
<%request.setCharacterEncoding(gb2312); %>
<HTML><HEAD>
<META http-equiv=Content-Type content=text/html; charset=gb2312>

<TITLE>级联菜单</TITLE>
<LINK rel=stylesheet type=text/css href=style.css>
</HEAD>

<%String sql=select * from Nclass order by NclassId asc;
ResultSet rs=stmt.executeQuery(sql);
%>

<script type=text/javascript>
var onecount;
onecount=0;
subcat = new Array();
        <%
        int count = 0;
        while(rs.next()){
        %>
subcat[<%=count%>] = new Array(<%=rs.getString(NclassName)%>,
<%=rs.getString(NclassId)%>,<%=rs.getString(parentId)%>);
        <%
        count++;
        }
        rs.close();
        %>
onecount=<%=count%>;

function changelocation(locationid)
    {
    document.myform.NclassId.length = 0;

    var locationid=locationid;
    var i;
    for (i=0;i < onecount; i++)
        {
            if (subcat[i][2] == locationid)
            {
                document.myform.NclassId.options[document.myform.NclassId.length] = new
Option(subcat[i][0], subcat[i][1]);
            }
        }

    }
</script>

<FORM method=POST name=myform action=adminsave.jsp?action=add>
<TABLE>

    <TR>
      <TD>一级分类</TD>
      <TD>
        <SELECT name=classId onChange=changelocation(document.myform.classId.options
[document.myform.classId.selectedIndex].value) size=1>
          <OPTION selected value>==请选一级分类==</OPTION>
        <sql:query var=query dataSource=$>
          SELECT * FROM class
       </sql:query>
<c:forEach var=row items=$>
<option value=$>$</option>
</c:forEach>
</select>
      </TD>
      <TD>选择二级分类</TD>
      <TD>
        <SELECT name=NclassId>
          <OPTION selected value>==请选二级分类==</OPTION>
        </SELECT>
      </TD>
    </TR>
</TABLE>

</FORM>
</BODY>
</HTML>
<%@ page contentType=text/html; charset=GB2312 language=java errorPage=../error.jsp %>
<%@ include file=../conn.jsp%>
<%@ include file=../ds.jsp%>
<%@ taglib uri=http://java.sun.com/jsp/jstl/sql divfix=sql %>
<%request.setCharacterEncoding(gb2312); %>
<HTML><HEAD>
<META http-equiv=Content-Type content=text/html; charset=gb2312>