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>
<!--从数据库中得到二级栏目信息-->
<%String sql=select * from Nclass order by NclassId asc;
ResultSet rs=stmt.executeQuery(sql);
%>
<!--将二级栏目信息保存到数组subcat中-->
<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%>;
<!--决定select显示的函数-->
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>
<TITLE>级联菜单</TITLE>
<LINK rel=stylesheet type=text/css href=style.css>
</HEAD>
<!--从数据库中得到二级栏目信息-->
<%String sql=select * from Nclass order by NclassId asc;
ResultSet rs=stmt.executeQuery(sql);
%>
<!--将二级栏目信息保存到数组subcat中-->
<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%>;
<!--决定select显示的函数-->
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>
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（责任编辑：云子）
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