日期:2014-05-17 浏览次数:20819 次
一般情况下,采用长连接,能持续的在客户端显示信息。
比如
<%@ page language="java" c pageEncoding="utf-8"%>
<%
out.flush();
int number = 0;
while (true) {
out.println(new java.util.Date()+"
");
out.flush();
Thread.sleep(100);
System.out.print(".");
if (number++ > 100) {
break;
}
}
%>
这个代码会在客户端连续的显示时间。请注意,浏览器的正在下载是一直在运行中的。这个会让客户感到疑惑,难道还有东西在运行吗?
下面的这个方法,可以解决这个问题
我们先看服务器端代码。
使用了prototype.js
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Comet php backend</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
<script type="text/javascript">
// KHTML browser don't share javascripts between iframes
var is_khtml = navigator.appName.match("Konqueror") || navigator.appVersion.match("KHTML");
if (is_khtml)
{
var prototypejs = document.createElement('script');
prototypejs.setAttribute('type','text/javascript');
prototypejs.setAttribute('src','../js/prototype.js');
var head = document.getElementsByTagName('head');
head[0].appendChild(prototypejs);
}
// load the comet object
var comet = window.parent.comet;
</script>
<%
out.flush();
int number = 0;
while (true) {
// 这里生成了调用js的代码
out.println("<script type='text/javascript'>comet.printServerTime('" + new java.util.Date() + "');</script>");
out.flush();
Thread.sleep(100);
// 控制台显示,程序正在运行,正式运行可去掉
System.out.print(".");
// 防止程序一直运行,给调试带来麻烦,正式运行可去掉
if (number++ > 100) {
break;
}
}
%>
关键在客户端代码
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Comet demo</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript" src="../js/prototype.js"></script>
</head>
<body>
<div id="content">The server time will be shown here</div>
<script type="text/javascript">
var url= 'testLinkData2.jsp';
var comet = {
connection : false,
iframediv : false,
initialize: function() {
if (navigator.appVersion.indexOf("MSIE") != -1) {
// For IE browsers
comet.connection = new ActiveXObject("htmlfile");
comet.connection.open();
comet.connection.write("<html>");
comet.connection.write("<script>document.domain = '"+document.domain+"'");
comet.connection.write("</html>");
comet.connection.close();
comet.iframediv = comet.connection.createElement("div");
comet.connection.appendChild(comet.iframediv);
comet.connection.parentWindow.comet = comet;
comet.iframediv.innerHTML = "<iframe id='comet_iframe' sr