如何利用Ajax实现地区三级联动详解

前言：

利用Ajax来实现一个地区的三级联动，用Java代码来读json文件，先eclipse做一个简单的，最基础的。（json我用的jackson来解析，也可用fastjson-阿里巴巴的等还有很多）提供代码，思路之类的，注释也没有自己去想去琢磨出来的思路好

first：首先先要熟悉json文件，并要想好利用什么类型去解析，这是最难的，最好找一个没人的地方戴上耳机（对于初学）我是用maven来做的用到的jar坐标 ：

redis.clientsjedis2.9.0compilejavax.servletjavax.servlet-api3.1.0providedcom.fasterxml.jackson.corejackson-databind2.11.2

文件位置：

second：首先创建一个html文件 three.html

加了一个字体居中和大小的样式以至于不会太难看，太原生

首先来实现–省–的局部刷新，利用Ajax

$(function(){$.post("province",function(data){$.each(data,function(){$("#province").append(""+this.name+"");})},"json")})

然后来写对应的ProvinceController.class的代码（主要是逻辑，为什么我要用List<Map>类型）

package com.daben.controller;import java.io.FileInputStream;import java.io.IOException;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.Map;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 com.fasterxml.jackson.core.type.TypeReference;import com.fasterxml.jackson.databind.ObjectMapper;@WebServlet("/province")public class ProvinceController extends HttpServlet{private static final long serialVersionUID = -6513954606070061277L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setContentType("appliaction/json;charset=utf-8");//可加可不加，json可在前端标注也可在后端 看自己习惯 我前后都加了ObjectMapper om = new ObjectMapper(); //jackson核心类String path = req.getServletContext().getRealPath("/WEB-INF/classes/city_code.json");//利用servletContext(也有叫appliaction)来拿到文件的真实路径，也可以利用加载器拿都一样FileInputStream fi = new FileInputStream(path);//流List<Map> province = om.readValue(fi, new TypeReference<List<Map>>() {});//jackson解析的方法，为什么是这个方法，百度学的 利用TypeReference可解析你想要得到的类型List<Map> list = new ArrayList();Iterator<Map> iterator = province.iterator();//我用的迭代器遍历的 foreach等 也可以 while(iterator.hasNext()) {Map map2 = iterator.next();map2.remove("city");//可写也可不写list.add(map2);}om.writeValue(resp.getWriter(), list);}}

在three.html添加改变事件

代码比较简单，就是跟简单的清空 赋值 取值

$("#province").on("change", function(){let code = $(this).find(":selected").val();$.post("city",{"code":code}, function(data){$("#city").empty();$("#city").append("---市---");$.each(data, function(){$("#city").append(""+this.name+"");})},"json");});

再写对应的CityController.class(代码类似)我为什么还会强转List<Map>类型

package com.daben.controller;import java.io.FileInputStream;import java.io.IOException;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.Map;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 com.fasterxml.jackson.core.type.TypeReference;import com.fasterxml.jackson.databind.ObjectMapper;@WebServlet("/city")public class CityController extends HttpServlet{private static final long serialVersionUID = -6513954606070061277L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req, resp);}@SuppressWarnings("unchecked")@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setContentType("appliaction/json;charset=utf-8");String code = req.getParameter("code");req.getSession().setAttribute("cityCode", code);ObjectMapper om = new ObjectMapper();String path = req.getServletContext().getRealPath("/WEB-INF/classes/city_code.json");FileInputStream fi = new FileInputStream(path);List<Map> province = om.readValue(fi, new TypeReference<List<Map>>() {});List<Map> list = new ArrayList();Iterator<Map> iterator = province.iterator();while(iterator.hasNext()) {Map map2 = iterator.next();if(map2.get("code").equals(code)) {map2.remove("code");map2.remove("name");list=(List<Map>) map2.get("city");break;}}List<Map> list1 = new ArrayList();Iterator<Map> iterator2 = list.iterator();while(iterator2.hasNext()) {Map next = iterator2.next();next.remove("area");list1.add(next);}om.writeValue(resp.getWriter(), list1);}}

不懂的话，可以先看一看city_code.json文件，多想一想

继续来three.html

$("#city").on("change", function(){let code = $(this).find(":selected").val();$.post("village",{"code":code}, function(data){$("#village").empty();$("#village").append("---县---");$.each(data, function(){$("#village").append(""+this.name+"");})},"json");

代码雷同以至于VillageController.class也是雷同，加了一些判断而已多了一个循环，

package com.daben.controller;import java.io.FileInputStream;import java.io.IOException;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.Map;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 com.fasterxml.jackson.core.type.TypeReference;import com.fasterxml.jackson.databind.ObjectMapper;@WebServlet("/village")public class VillageController extends HttpServlet{private static final long serialVersionUID = -6513954606070061277L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req, resp);}@SuppressWarnings("unchecked")@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setContentType("appliaction/json;charset=utf-8");String code = req.getParameter("code");String cityCode = (String)req.getSession().getAttribute("cityCode");ObjectMapper om = new ObjectMapper();String path = req.getServletContext().getRealPath("/WEB-INF/classes/city_code.json");FileInputStream fi = new FileInputStream(path);List<Map> province = om.readValue(fi, new TypeReference<List<Map>>() {});List<Map> list = new ArrayList();Iterator<Map> iterator = province.iterator();while(iterator.hasNext()) {Map map2 = iterator.next();if(map2.get("code").equals(cityCode)) {map2.remove("code");map2.remove("name");list=(List<Map>) map2.get("city");break;}}List<Map> list1 = new ArrayList();Iterator<Map> iterator2 = list.iterator();while(iterator2.hasNext()) {Map next = iterator2.next();if(next.get("code").equals(code)) {next.remove("code");next.remove("name");list1 = (List<Map>)next.get("area");}}om.writeValue(resp.getWriter(), list1);}}

完结：只提供了代码，但是为什么这样何不自己去想一想？

json地区文件下载：

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↑关注上方公众号回复 “201231” 即可下载↑

思考？可不可以用xml文件来代替json文件？将jackson换成jsoup来解析？

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