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> <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>

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