Ajax(5):利用json做数据交换

来源：互联网发布：太平洋网站软件下载编辑：程序博客网时间：2024/04/30 09:13

工程目录：

show.jsp :

<%@ page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8"%><html><head><title>Insert title here</title><script type="text/javascript" src="js/prototype1.6.js"></script><script>function getXmlHttpRequest(){var xhr=null;if((typeof XMLHttpRequest)!='undefined'){xhr=new XMLHttpRequest();}else{xhr=new ActiveXObject("Microsoft.XMLHttp");}return xhr;}var intervalId;function show(){intervalId=setInterval(getShareInfo,1000);}function stopShow(){clearInterval(intervalId);}function getShareInfo(){var xhr=getXmlHttpRequest();xhr.onreadystatechange=function(){if(xhr.readyState==4){var jsonStr=xhr.responseText;var share=jsonStr.evalJSON();$('d1').innerHTML="股票名称:"+share.shareName+"<br>股票价格:"+share.sharePrice+"<br>时间:"+share.date;}}xhr.open("post","show",true);xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");xhr.send(null);}</script></head><body onload="show();"><div style="width:250px;height:70px;border:1px solid black" id="d1"></div><input type="button" value="停止报价" onclick="stopShow();"></body></html>

Share.java :

public class Share {private String shareName;private double sharePrice;private Date date;public Date getDate() {return date;}public void setDate(Date date) {this.date = date;}public String getShareName() {return shareName;}public void setShareName(String shareName) {this.shareName = shareName;}public double getSharePrice() {return sharePrice;}public void setSharePrice(double sharePrice) {this.sharePrice = sharePrice;}public Share() {super();}public Share(String shareName, double sharePrice, Date date) {super();this.shareName = shareName;this.sharePrice = sharePrice;this.date = date;}}

DateProcessor.java :

public class DateProcessor implements JsonValueProcessor {private String pattern="yyyy-MM-dd HH:mm:ss";public void setPattern(String pattern) {this.pattern = pattern;}@Overridepublic Object processArrayValue(Object arg0, JsonConfig arg1) {Date date=(Date)arg0;SimpleDateFormat sdf=new SimpleDateFormat(pattern);return sdf.format(date);}@Overridepublic Object processObjectValue(String arg0, Object arg1, JsonConfig arg2) {Date date=(Date)arg1;SimpleDateFormat sdf=new SimpleDateFormat(pattern);return sdf.format(date);}}

ShowServlet.java :

public class ShowServlet extends HttpServlet {public void service(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {Random random=new Random();String shareName="share"+random.nextInt(99999);double sharePrice=Math.ceil(random.nextDouble()*10);Share share=new Share(shareName,sharePrice,new Date());DateProcessor processor=new DateProcessor();JsonConfig config=new JsonConfig();config.registerJsonValueProcessor(Date.class,processor);JSONObject json=JSONObject.fromObject(share,config);response.setContentType("text/html;charset=UTF-8");PrintWriter pw=response.getWriter();pw.println(json.toString());pw.close();}}

为ShowServlet映射的url为show。

数据转换涉及两个过程：

① 服务器端将Java对象Share转换为符合json语法的字符串，并发送给客户端。

② 浏览器接收到符合json语法的字符串，利用evalJSON( )函数将字符串转换为JavaScript对象，并及时更新页面数据。

当然，上面的程序在实际中无意义，它仅仅为了演示json是如何做数据交换的。