JSP+JavaScript打造二級級聯下拉式選單：
class(一級欄位資訊）：classId(自動編號），className（欄位名稱）, Nclass（二級欄位資訊）, NclassId（自動編號），NclassName(欄位名稱） ，parentId（一級欄位id，與class表中的classId關聯）
<%@ 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>級聯選單</TITLE>
<LINK rel=stylesheet type=text/css href=style.css>
</HEAD>
<!--從資料庫中得到二級欄位資訊-->
<%String sql=select * from Nclass order by NclassId asc;
ResultSet rs=stmt.executeQuery(sql);
%>
<!--將二級欄位資訊儲存到陣列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%>;
<!--決定select顯示的函數-->
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>一級分類</TD>
<TD>
<SELECT name=classId onChange=changelocation(document.myform.classId.options
[document.myform.classId.selectedIndex].value) size=1>
<OPTION selected value>==請選一級分類==</OPTION>
<sql:query var=query dataSource=$>
SELECT * FROM class
</sql:query>
<c:forEach var=row items=$>
<option value=$>$</option>
</c:forEach>
</select>
</TD>
<TD>選擇二級分類</TD>
<TD>
<SELECT name=NclassId>
<OPTION selected value>==請選二級分類==</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>級聯選單</TITLE>
<LINK rel=stylesheet type=text/css href=style.css>
</HEAD>
<!--從資料庫中得到二級欄位資訊-->
<%String sql=select * from Nclass order by NclassId asc;
ResultSet rs=stmt.executeQuery(sql);
%>
<!--將二級欄位資訊儲存到陣列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%>;
<!--決定select顯示的函數-->
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>一級分類</TD>
<TD>
<SELECT name=classId onChange=changelocation(document.myform.classId.options
[document.myform.classId.selectedIndex].value) size=1>
<OPTION selected value>==請選一級分類==</OPTION>
<sql:query var=query dataSource=$>
SELECT * FROM class
</sql:query>
<c:forEach var=row items=$>
<option value=$>$</option>
</c:forEach>
</select>
</TD>
<TD>選擇二級分類</TD>
<TD>
<SELECT name=NclassId>
<OPTION selected value>==請選二級分類==</OPTION>
</SELECT>
</TD>
</TR>
</TABLE>
</FORM>
</BODY>
</HTML>