使用Ajax实现省市县三级联动

首先建立数据库，如下所示

接口

省

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

市

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

县

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

接口实现类

省

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;
    }
}

市

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;
    }
}

县

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;
    }
}

servlet
省

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);
    }
}

市

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);
    }
}

县

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);
    }
}

JSP页面

<%@ 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>

实现结果如下：