Ajax二级联动菜单实现原理及代码

< page language="java" pageEncoding="UTF-8"

package com;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/***
*
* @author zdw
*
*/
public class SelectServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
public SelectServlet()
{
super();
}
public void destroy()
{
super.destroy();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
// response.setCharacterEncoding("GBK");
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
request.setCharacterEncoding("GBK");
response.setCharacterEncoding("UTF-8");
String targetId = request.getParameter("id").toString();
System.out.println(targetId);
// 获得请求中参数为id的值
String xml_start = "";
String xml_end = "";
String xml = "";
if (targetId.equalsIgnoreCase("0"))
{
xml = "0请选择";
} else if (targetId.equalsIgnoreCase("1"))
{
xml = "1昌平";
xml += "2丰台";
xml += "3海淀";
xml += "4朝阳";
} else if (targetId.equalsIgnoreCase("2"))
{
xml = "1塘沽区";
xml += "2汉沽区";
xml += "3大港区";
xml += "4东丽区";
} else
{// 如果是3,则返回下面的字符
xml = "1济南";
xml += "2青岛";
xml += "3淄博";
xml += "4枣庄";
}
String last_xml = xml_start + xml + xml_end;
response.getWriter().write(last_xml);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
doGet(request, response);
}
public void init() throws ServletException
{
}
}

<?xml version="1.0" encoding="UTF-8"?>
xmlns:xsi="/d/jc/2022091703/394943kuuhznwbq4g"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
/d/jc/2022091703/4049443wtakvsk5k5

SelectServlet
com.SelectServlet


SelectServlet
/select


index.jsp