Ajax实现不刷屏的前提下实现定时刷新-技术开发专区

Ajax实现不刷屏的前提下实现定时刷新

作者：ITPUB论坛编辑： nancy 2008-02-14 00:00

【IT168技术文档】

主页面（要求刷新的页面）要求每一分钟刷新一次系统时间

<html>
<body onload="makeRequest("getSystemTime.jsp")"> //创建httpRequest对象
<form name="dateForm">
<table>
<td colspan="2" align="center">
<div id="sysTimeShow"></div> //显示平台系统时间
</td>
</table></form>
</body>
</html>
getSystemTime.jsp     //获得系统的当前时间，也就是输出结果的页面
<%@ page language="java"  %>
<%@ page contentType="text/html;charset=GB2312" %>
<%@ page import="java.util.Date"%>
<%@ page import="java.sql.Timestamp"%>
<%@ page import="java.io.IOException"%>
<%
Date d = new Date();
Timestamp ts = new Timestamp(d.getTime());
String result = ts.toString().substring(0,16);
out.write(result,0,result.length());
%>

ajax.js

function makeRequest(url) {
http_request = false;
if (window.XMLHttpRequest) {
http_request = new XMLHttpRequest();
if (http_request.overrideMimeType){
http_request.overrideMimeType('text/xml');
}
} else if (window.ActiveXObject) {
try{
http_request = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
http_request = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {
}
}
}
if (!http_request) {
alert("您的浏览器不支持当前操作，请使用 IE 5.0 以上版本!");
return false;
}
//定义页面调用的方法init,不是init();没有();
 http_request.onreadystatechange = init;
http_request.open('GET', url, true);
//禁止IE缓存
 http_request.setRequestHeader("If-Modified-Since","0");
//发送数据
 http_request.send(null);
//每60秒刷新一次页面
 setTimeout("makeRequest('"+url+"')", 60000);
}
function init() {
if (http_request.readyState == 4) {
if (http_request.status == 0 || http_request.status == 200) {
var result = http_request.responseText;
if(result==""){
result = "系统时间获取失败";
}
document.getElementById ("sysTimeShow").innerHTML="平台系统时间："+result;
} else {//http_request.status != 200
   alert("请求失败!");
}
}
}

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