日期:2014-05-17 浏览次数:20609 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