Detailed explanation of Ajax implementation of three-level cascade in provinces and municipalities

This article mainly introduces Ajax to realize the three-level cascade of provinces and municipalities. The data comes from the mysql database and has certain reference value. Interested friends can refer to it. I hope it can help everyone.

To implement Ajax to achieve three-level cascading of provinces and municipalities, Java parsing json technology is required
The overall Demo download address is as follows: Click me to download

address.html

 

 
  请选择省
 
 
  请选择市
 
 
  请选择市
 
 
 确定
 

AddressServlet.java

package cn.bestchance.servlet;

import java.io.IOException;
import java.util.ArrayList;

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 cn.bestchance.dao.AddressDao;
import cn.bestchance.dao.impl.AddressDaoImpl;
import cn.bestchance.entity.Address;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

@WebServlet("/addressSerlvet")
public class AddressSerlvet extends HttpServlet {
 private static final long serialVersionUID = 1L;
 private AddressDao dao = new AddressDaoImpl();

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

 /**
  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
  *  response)
  */
 protected void doPost(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {

  response.setCharacterEncoding("utf-8");
  response.setContentType("text/html;charset=utf-8");
  String method=request.getParameter("method");
  if("provincial".equals(method)){
   getProvincial(request, response);
  }
  if("city".equals(method)){
   getCity(request, response);
  }
  if("area".equals(method)){
   getArea(request, response);
  }
 }
 /**
  * 根据市id获取该市下的区的全部信息
  * @param request
  * @param response
  * @throws ServletException
  * @throws IOException
  */
 protected void getArea(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {

  String cityId = request.getParameter("cityId");
  // 从数据库中查询省的信息
  ArrayList
 areaList = dao.getAreaByCityId(Integer.parseInt(cityId));
  // 将集合转成json字符串
  JSONObject jsonObj = new JSONObject();
  JSONArray jsonArray = JSONArray.fromObject(areaList);
  jsonObj.put("areaList", jsonArray);
  String jsonDataStr = jsonObj.toString();

  response.getWriter().print(jsonDataStr);
 }
 /**
  * 获取省的信息 并相应
  * @param request
  * @param response
  * @throws ServletException
  * @throws IOException
  */
 protected void getProvincial(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {

  // 从数据库中查询省的信息
  ArrayList
 addrList = dao.getProvince();
  // 将集合转成json字符串
  JSONObject jsonObj = new JSONObject();
  JSONArray jsonArray = JSONArray.fromObject(addrList);
  jsonObj.put("addrList", jsonArray);
  String jsonDataStr = jsonObj.toString();
  response.getWriter().print(jsonDataStr);
 }
 /**
  * 获取市的信息并相应
  * @param request
  * @param response
  * @throws ServletException
  * @throws IOException
  */
 protected void getCity(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {

  String provinceId = request.getParameter("provincial");
  // 从数据库中查询省的信息
  ArrayList
 addrList = dao.getCityByProvinceId(Integer.parseInt(provinceId));

  // 将集合转成json字符串
  JSONObject jsonObj = new JSONObject();
  JSONArray jsonArray = JSONArray.fromObject(addrList);
  jsonObj.put("cityList", jsonArray);
  String jsonDataStr = jsonObj.toString();

  response.getWriter().print(jsonDataStr);
 }

}

AddressDao.java

##

package cn.bestchance.dao;

import java.util.ArrayList;

import cn.bestchance.entity.Address;

public interface AddressDao {
 /**
  * 获取省的id和名称
  * @return
  */
 ArrayList
 getProvince();
 /**
  * 根据省的id获取市的信息
  * @param provinceId
  * @return
  */
 ArrayList
 getCityByProvinceId(int provinceId);
 /**
  * 根据市的id获取区的信息
  * @param cityId
  * @return
  */
 ArrayList
 getAreaByCityId(int cityId);
}

AddressDaoImpl.java

package cn.bestchance.dao.impl;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;

import cn.bestchance.dao.AddressDao;
import cn.bestchance.entity.Address;
import cn.bestchance.util.DBUtil;

public class AddressDaoImpl implements AddressDao {
 private DBUtil db = new DBUtil();
 @Override
 public ArrayList
 getProvince() {
  ArrayList
 addrList = new ArrayList
();
  db.openConnection();
  String sql = "select * from province";
  ResultSet rs = db.excuteQuery(sql);
  try {
   while(rs.next()){
    Address addr = new Address();
    addr.setId(rs.getInt(2));
    addr.setAddress(rs.getString(3));
    addrList.add(addr);
   }
  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }finally{
   if(rs != null){
    try {
     rs.close();
    } catch (SQLException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   }
   db.closeResoure();
  }
  return addrList;
 }
 @Override
 public ArrayList
 getCityByProvinceId(int provinceId) {
  ArrayList
 addrList = new ArrayList
();
  db.openConnection();
  String sql = "select * from city where fatherID = " + provinceId; //431200
  ResultSet rs = db.excuteQuery(sql);
  try {
   while(rs.next()){
    Address addr = new Address();
    addr.setId(rs.getInt(2));
    addr.setAddress(rs.getString(3));
    addrList.add(addr);
   }
  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }finally{
   if(rs != null){
    try {
     rs.close();
    } catch (SQLException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   }
   db.closeResoure();
  }
  return addrList;
 }
 @Override
 public ArrayList
 getAreaByCityId(int cityId) {
  ArrayList
 addrList = new ArrayList
();
  db.openConnection();
  String sql = "select * from area where fatherID = " + cityId; //431200
  ResultSet rs = db.excuteQuery(sql);
  try {
   while(rs.next()){
    Address addr = new Address();
    addr.setId(rs.getInt(2));
    addr.setAddress(rs.getString(3));
    addrList.add(addr);
   }
  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }finally{
   if(rs != null){
    try {
     rs.close();
    } catch (SQLException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   }
   db.closeResoure();
  }
  return addrList;
 }

}

Entity class Address.java

##

package cn.bestchance.entity;

public class Address {
 @Override
 public String toString() {
  return "Address [id=" + id + ", address=" + address + "]";
 }
 private int id;
 private String address;
 public int getId() {
  return id;
 }
 public void setId(int id) {
  this.id = id;
 }
 public String getAddress() {
  return address;
 }
 public void setAddress(String address) {
  this.address = address;
 }
 public Address() {
  super();
  // TODO Auto-generated constructor stub
 }
 public Address(int id, String address) {
  super();
  this.id = id;
  this.address = address;
 }

}

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