对于页面一直监控,以前都是使用ajax请求即可,但是小并发这做法没多大问题,但是到了大并发就不太合适,如果不想自己写线程来操控就可以偷懒找一些插件,例如comet4j
下面我来演示下如何使用这个插件
先准备需要的工具:
comet4j-tomcat6.jar(tomcat6的就导入这个)
comet4j-tomcat7.jar(tomcat7的就导入这个)
comet4j.js(页面引入这个js)
具体操作看下面
然后就写个class
package com.shadow.extras.comet4j;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import org.comet4j.core.CometContext;
import org.comet4j.core.CometEngine;
public class TestComet implements ServletContextListener {
private static final String CHANNEL = "test";
private static final String CHANNEL2 = "test2";
public void contextInitialized(ServletContextEvent arg0) {
CometContext cc = CometContext.getInstance();
cc.registChannel(CHANNEL);// 注册应用的channel
cc.registChannel(CHANNEL2);
Thread helloAppModule = new Thread(new HelloAppModule(),
"Sender App Module");
// 是否启动
helloAppModule.setDaemon(true);
// 启动线程
helloAppModule.start();
Thread helloAppModule2 = new Thread(new HelloAppModule2(),
"Sender App Module");
// 是否启动
helloAppModule2.setDaemon(true);
// 启动线程
helloAppModule2.start();
}
class HelloAppModule2 implements Runnable {
public void run() {
while (true) {
try {
// 睡眠时间
Thread.sleep(5000);
} catch (Exception ex) {
ex.printStackTrace();
}
CometEngine engine = CometContext.getInstance().getEngine();
// 获取消息内容
long l = getFreeMemory();
// 开始发送
engine.sendToAll(CHANNEL2, l);
}
}
}
class HelloAppModule implements Runnable {
public void run() {
while (true) {
try {
// 睡眠时间
Thread.sleep(2000);
} catch (Exception ex) {
ex.printStackTrace();
}
CometEngine engine = CometContext.getInstance().getEngine();
// 获取消息内容
long l = getFreeMemory();
// 开始发送
engine.sendToAll(CHANNEL, l);
}
}
}
public void contextDestroyed(ServletContextEvent arg0) {
}
public long getFreeMemory() {
return Runtime.getRuntime().freeMemory() / 1024;
}
}
然后再写个页面
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Comet4J Hello World</title>
<script type="text/javascript" src="plugin/comet4j/comet4j.js"></script>
<script type="text/javascript">
function init(){
var kbDom = document.getElementById('kb');
var kbDom2 = document.getElementById('kb2');
JS.Engine.on({
test : function(aa){//侦听一个channel
kbDom.innerHTML = aa;
},
test2 : function(bb){
kbDom2.innerHTML = bb;
}
});
JS.Engine.start('comet');
}
</script>
</head>
<body onload="init()">
剩余内存：<span id="kb">...</span>KB <br/>
剩余内存：<span id="kb2">...</span>KB
</body>
</html>
接着配置下web.xml就ok了
<!-- comet4j --> <listener> <description>Comet4J容器侦听</description> <listener-class>org.comet4j.core.CometAppListener</listener-class> </listener> <servlet> <description>Comet连接[默认:org.comet4j.core.CometServlet]</description> <display-name>CometServlet</display-name> <servlet-name>CometServlet</servlet-name> <servlet-class>org.comet4j.core.CometServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CometServlet</servlet-name> <url-pattern>/comet</url-pattern> </servlet-mapping> <listener> <description>TestComet</description> <listener-class>com.shadow.extras.comet4j.TestComet</listener-class> </listener>
最后修改下tomcat的server.xml文件
把protocol参数值改成下面的,因为这是基于nio开发的插件
<Connector URIEncoding="UTF-8" connectionTimeout="20000" port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol" redirectPort="8443"/>
测试,很简单就是访问我们刚刚创建的test.html,然后就可以看到内存数值一直自动刷新波动
