js之第三方工具解析JSON

来源：互联网发布：实景建模软件编辑：程序博客网时间：2024/05/21 20:27

1.JSON 只是一种文本字符串。它被存储在 responseText 属性中

为了读取存储在 responseText 属性中的 JSON 数据，需要根据 JavaScript 的 eval 函数。函数 eval 会把一个字符串当作它的参数。然后这个字符串会被当作 JavaScript 代码来执行。因为 JSON 的字符串就是由 JavaScript 代码构成的，所以它本身是可执行的

例如如下方式:

String json = "{username:'一叶扁舟',age:22}";var  json = xhr.responseText;json = eval("("+json+")");alert(json.name);

2.利用第三方工具解析JSON

(1).需要导入的jar包

(2)代码实战:
domain实体类：

package com.wenhao.web.ajax.domain;/** *类的作用：City实体类 * * *@author 一叶扁舟 *@version 1.0 *@创建时间： 2014-10-28   下午05:57:18 *///城市[JavaBean]public class City {private int id;private String cityName;public City(){}public City(int id, String cityName) {super();this.id = id;this.cityName = cityName;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getCityName() {return cityName;}public void setCityName(String cityName) {this.cityName = cityName;}}

servlet服务处理:

package com.wenhao.web.ajax.servlet;import java.io.IOException;import java.io.PrintWriter;import java.util.ArrayList;import java.util.List;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import net.sf.json.JSONArray;import net.sf.json.JsonConfig;import com.wenhao.web.ajax.domain.City;/** *类的作用：JavaBean直接转成JSON对象 *这个是json传输 * * *@author 一叶扁舟 *@version 1.0 *@创建时间： 2014-10-28   下午05:58:20 */public class CityServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String province = request.getParameter("province");byte[] buf = province.getBytes("ISO8859-1");province = new String(buf,"UTF-8");response.setContentType("text/html;charset=UTF-8");PrintWriter pw = response.getWriter();List<City> cityList = new ArrayList<City>();String jsonString = null;if(province.equals("河南省")){cityList.add(new City(1,"郑州"));cityList.add(new City(2,"洛阳"));cityList.add(new City(3,"开封"));cityList.add(new City(4,"信阳"));}else if(province.equals("福建省")){cityList.add(new City(1,"福州"));cityList.add(new City(2,"厦门"));cityList.add(new City(3,"莆田"));cityList.add(new City(4,"漳州"));cityList.add(new City(5,"龙岩"));}else if(province.equals("云南省")){cityList.add(new City(1,"大理"));cityList.add(new City(2,"昆明"));cityList.add(new City(3,"香格里拉"));}JsonConfig jsonConfig = new JsonConfig();//json数据中不包含id属性jsonConfig.setExcludes(new String[]{"id"});//将cityList转成json数组JSONArray jsonArray = JSONArray.fromObject(cityList,jsonConfig);jsonString = jsonArray.toString();System.out.println("jsonString="+jsonString);pw.write(jsonString);}}

jsp界面获取json数据:

<%@ page language="java" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head><meta http-equiv="content-type" content="text/html; charset=UTF-8">  </head>  <body><select id="provinceID"><option>选择省份</option><option>河南省</option><option>福建省</option><option>云南省</option></select><select id="cityID"><option>选择城市</option></select><script type="text/javascript">document.getElementById("provinceID").onchange=function(){//清空原city列表框var citySelectElement = document.getElementById("cityID");var cityElementArray = citySelectElement.options;var size = cityElementArray.length;if(size > 1){//从后向前删除下拉列表框中的东西for(var i=size-1;i>0;i--){citySelectElement.removeChild(cityElementArray[i]);}}var province = this[this.selectedIndex].innerHTML;province = encodeURI(province);var xhr = createXHR();xhr.onreadystatechange = function(){if(xhr.readyState==4){if(xhr.status==200){//取得json字符串var jsonString = xhr.responseText;//将json字符串转成json对象var jsonObject = eval("("+jsonString+")");var size = jsonObject.length;for(var i=0;i<size;i++){var city = jsonObject[i].cityName;var optionElement = document.createElement("option");optionElement.innerHTML = city;document.getElementById("cityID").appendChild(optionElement);}}}}xhr.open("get","/FirstAjax/CityServlet?time="+new Date().getTime()+"&province="+province);xhr.send(null);};//创建一个ajax对象function createXHR(){var xhr = null;//如果是IE浏览器if(window.ActiveXObject){xhr = new ActiveXObject("microsoft.xmlhttp");}else{//非IE浏览器xhr = new XMLHttpRequest();}return xhr;}</script>  </body></html>

测试效果图:

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