单表，三级联动选择菜单 ajax，jsp，

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta http-equiv="Content-type" content="text/html; charset=utf-8"><title>多级联动菜单</title><mce:script type="text/javascript"></mce:script></head><body onload="initSelArray('selA','selB','selC');buildSelect('0', 'selA')"><h1>多级联动菜单</h1> <form> <select name="selA" id="selA" onchange="buildSelect(this.value, 'selB')"> <option value="" selected>----请选择----</option> </select> <select name="selB" id="selB" onchange="buildSelect(this.value, 'selC')"> <option value="" selected>----请选择----</option> </select> <select name="selC" id="selC"> <option value="" selected>----请选择----</option> </select> </form></body></html>

jsp code

<%@ page contentType="text/plain; charset=UTF-8"%><%@ page language="java"%><%@ page import="java.sql.*,com.ldc.shopping.util.*"%><%! //访问数据库取得下级选项信息 String getOptions(String selectedId) { int counter = 0; //计数器 StringBuffer opts = new StringBuffer("{"); //保存选项信息 String sql = "select * from category where pid = ? order by cno asc";//定义查询数据库的SQL语句 Connection conn = null; //声明Connection对象 PreparedStatement pstmt = null; //声明PreparedStatement对象 ResultSet rs = null; //声明ResultSet对象 try { conn = DB.getConn(); //获取数据库连接 pstmt = conn.prepareStatement(sql); //根据sql创建PreparedStatement pstmt.setString(1, selectedId); //设置参数 rs = pstmt.executeQuery(); //执行查询，返回结果集 while (rs.next()) { //遍历结果集 //如果不是第一项，追加一个“,”用于分隔选项 if (counter > 0) { opts.append(","); } opts.append("'"); opts.append(rs.getString("id")); opts.append("':'"); if(selectedId.equals("0")){ opts.append(rs.getString("name")+"-->"); }else{ opts.append(rs.getString("name")); } opts.append("'"); counter++; //计数器加1 } } catch (SQLException e) { System.out.println(e.toString()); } finally { DB.close(rs); //关闭结果集 DB.close(pstmt); //关闭PreparedStatement DB.close(conn); //关闭连接 } opts.append("}"); return opts.toString(); }%><% out.clear(); //清空当前的输出内容（空格和换行符） String selectedId = request.getParameter("selectedId"); //获取selectedId参数 String optionsInfo = getOptions(selectedId); //调用getOptions方法取得下级选项信息 out.print(optionsInfo); //输出下级选项信息%>

表结构 |----id----pid----name---|

|_____|____|_______|