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xsy1994
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Ajax实现自动更新页面（不刷新页面更新网页内容）

    博客分类：
  • AJAX
AjaxServletOracleJSPXML 
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Ajax实现自动更新页面（不刷新页面更新网页内容）
1.使用XMLHttpRequest向服务器发送请求，接受信息改变网页中某些元素的内容；
2.使用setTimeout设置重复发送请求间隔时间，起到自动更新页面的效果；

refresh.html:
程序代码

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>Refresh</title>
    <script type="text/javascript" src="js/refresh.js"></script>
</head>
<body>
    <h2>Ajax Dynamic Update</h2>
    <input type="button" value="START" onClick="doStart();" />
    <br />
    Page will refresh in <span id="time">3</span> seconds.
    <br /><br />
    <div id="show" style="font-size:40px;"></div>
</body>
</html>


refresh.js:
程序代码

var xmlHttp;
var time = 3;

function createXMLHttpReqeust() {
    if (window.ActiveXObject) {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    } else if (window.XMLHttpRequest) {
        xmlHttp = new XMLHttpRequest();
    }
}

function doStart() {
   
    doPost();
    refreshTime();
}

function doPost() {
    createXMLHttpReqeust();
    xmlHttp.onreadystatechange = callback;
    var url = "refresh.mgc?timestamp=" + new Date().getTime();
    xmlHttp.open("GET", url, true);
    xmlHttp.send(null);
    setTimeout("doPost()", "3000");
}

function callback() {
    if (xmlHttp.readyState == 4) {
        if (xmlHttp.status == 200) {
            parseResult();
        }
    }
}

function parseResult() {
    var show = document.getElementById("show");
    show.innerHTML = xmlHttp.responseText;
}

function refreshTime() {
    document.getElementById("time").innerHTML = time--;
    if (time < 1) {
        time = 3;
    }
    setTimeout("refreshTime()", "1000");
}


Refresh.java:
程序代码

package cn.edu.ahau.mgc.ajax.refresh;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Refresh extends HttpServlet {

    private int i;
    private String[] str = {"JSP", "Servlet", "Ajax", "Oracle"};
   
    @Override
    public void init() throws ServletException {
        super.init();
        this.i = 0;
    }

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

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       
        response.setContentType("text/xml");
        response.setHeader("Cache-Control", "no-cache");
        PrintWriter out = response.getWriter();
        out.print(this.str[this.i]);
        out.flush();
        out.close();
        if (++i > 3) {
            i = 0;
        }
    }

}


web.xml:
程序代码

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
    xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>Refresh</servlet-name>
    <servlet-class>cn.edu.ahau.mgc.ajax.refresh.Refresh</servlet-class>
  </servlet>





  <servlet-mapping>
    <servlet-name>Refresh</servlet-name>
    <url-pattern>/refresh.mgc</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>


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