Ajax实现省市县三级联动

import java.util.List;
public interface ProvinceDao {
 List<Province> findAll();
}

import java.util.List;
public interface CityDao {
 List<City> findCityByPid(int pid);
}

import java.util.List;
public interface AreaDao {
 List<Area> findAreaByCid(int cid);
}

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class ProvinceDaoImpl implements ProvinceDao{
 public List<Province> findAll(){
 Connection conn = DBHelper.getConn();
 ArrayList<Province> provinces = new ArrayList<Province>();
 String sql = "select * from aprovince";
 try {
 PreparedStatement ps = conn.prepareStatement(sql);
 ResultSet rs = ps.executeQuery();
 while (rs.next()){
 Province p = new Province();
 p.setPid(rs.getInt(1));
 p.setPname(rs.getString(2));
 provinces.add(p);
 }
 } catch (SQLException e) {
 e.printStackTrace();
 }
 return provinces;
 }
}

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class CityDaoImpl implements CityDao {
 @Override
 public List<City> findCityByPid(int pid) {
 Connection conn = DBHelper.getConn();

 ArrayList<City> cities = new ArrayList<>();

 String sql = "select * from acity where pid=?";

 try {
 PreparedStatement ps = conn.prepareStatement(sql);
 ps.setInt(1,pid);
 ResultSet rs = ps.executeQuery();
 while (rs.next()){
 City city = new City();
 city.setPid(rs.getInt(3));
 city.setCid(rs.getInt(1));
 city.setCname(rs.getString(2));
 cities.add(city);
 }
 } catch (SQLException e) {
 e.printStackTrace();
 }
 return cities;
 }
}

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class AreaDaoImpl implements AreaDao {
 @Override
 public List<Area> findAreaByCid(int cid) {
 Connection conn = DBHelper.getConn();
 ArrayList<Area> areas = new ArrayList<>();
 String sql = "select * from aarea where cid=?";

 try {
 PreparedStatement ps = conn.prepareStatement(sql);
 ps.setInt(1,cid);
 ResultSet rs = ps.executeQuery();
 while (rs.next()){
 Area area = new Area();
 area.setCid(rs.getInt(3));
 area.setAid(rs.getInt(1));
 area.setAname(rs.getString(2));
 areas.add(area);
 }
 } catch (SQLException e) {
 e.printStackTrace();
 }
 return areas;
 }
}

package cn.zhc.servlet;

import cn.zhc.dao.Impl.ProvinceDaoImpl;
import cn.zhc.dao.ProvinceDao;
import cn.zhc.domin.Province;
import com.alibaba.fastjson.JSONObject;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet("/findAll")
public class FindAll extends HttpServlet {
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 request.setCharacterEncoding("utf-8");
 response.setContentType("text/html;charset=utf-8");

 ProvinceDao provinceDao = new ProvinceDaoImpl();
 List<Province> lists=provinceDao.findAll();

 response.getWriter().write(JSONObject.toJSONString(lists));
 }
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 this.doPost(request, response);
 }
}

package cn.zhc.servlet;

import cn.zhc.dao.CityDao;
import cn.zhc.dao.Impl.CityDaoImpl;
import cn.zhc.domin.City;
import com.alibaba.fastjson.JSONObject;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet("/findCityByPid")
public class FindCityByPid extends HttpServlet {
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 request.setCharacterEncoding("utf-8");
 response.setContentType("text/html;charset=utf-8");

 String pid = request.getParameter("pid");

 CityDao cityDao = new CityDaoImpl();
 List<City> cityList = cityDao.findCityByPid(Integer.parseInt(pid));

 response.getWriter().write(JSONObject.toJSONString(cityList));
 }

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 this.doPost(request, response);
 }
}

package cn.zhc.servlet;

import cn.zhc.dao.AreaDao;
import cn.zhc.dao.Impl.AreaDaoImpl;
import cn.zhc.domin.Area;
import com.alibaba.fastjson.JSONObject;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet("/findAreaByCid")
public class FindAreaByCid extends HttpServlet {
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 request.setCharacterEncoding("utf-8");
 response.setContentType("text/html;charset=utf-8");

 String cid = request.getParameter("cid");

 AreaDao areaDao = new AreaDaoImpl();
 List<Area> areas = areaDao.findAreaByCid(Integer.parseInt(cid));

 response.getWriter().write(JSONObject.toJSONString(areas));
 }

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 this.doPost(request, response);
 }
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
 <title>三级联动</title>
 <script type="text/javascript" src="js/jquery-1.8.3.js"></script>
</head>
<body>
<script type="text/javascript">
 $(function () {
 $.ajax({
 type:"get",
 url:"findAll",
 dataType:"json",
 success:function (data) {
 var obj=$("#province");
 for(var i=0;i<data.length;i++){
 var ob="<option value='"+data[i].pid+"'>"+data[i].pname+"</option>";
 obj.append(ob);
 }
 }
 })

 $("#province").change(function () {
 $("#city option").remove();
 $.ajax({
 type:"get",
 async:false,
 url:"findCityByPid?pid="+$("#province").val(),
 dataType:"json",
 success:function (data) {
 var obj=$("#city");
 for(var i=0;i<data.length;i++){
 var ob="<option value='"+data[i].cid+"'>"+data[i].cname+"</option>";
 obj.append(ob);
 }
 }
 })
 });

 $("#city,#province").change(function () {
 $("#area option").remove();
 $.ajax({
 type:"get",
 async:false,
 url:"findAreaByCid?cid="+$("#city").val(),
 dataType:"json",
 success:function (data) {
 var obj=$("#area");
 for(var i=0;i<data.length;i++){
 var ob="<option value='"+data[i].aid+"'>"+data[i].aname+"</option>";
 obj.append(ob);
 }
 }
 })
 });
 });
</script>
<select name="province" id="province">
 <option value="0">请选择</option>
</select>省
<select name="city" id="city">
 <option value="0">请选择</option>
</select>市
<select name="area" id="area">
 <option value="0">请选择</option>
</select>县
</body>
</html>