Comet4J 消息推送
宗烨赫
准备工作
1.下载服务端jar文件
Comet4J目前仅支持Tomcat6、7版本，根据您所使用的Tomcat版本下载【comet4j-tomcat6.jar】或【comet4j-tomcat7.jar】文件放置到WEB项目的WEB-INF\lib目录下。
2.下载客户端js文件
下载【comet4j.js】到您的项目中，比如：WebContent\js目录下。
3.修改服务器配置文件
因为Comet4J工作在NIO方式下，所以我们需要调整服务器连接器配置，更换为NOI连接器。 打开server.xml文件将找到原先的连接器配置：<Connector executor="tomcatThreadPool" port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" />替换为：<Connector URIEncoding="UTF-8" connectionTimeout="20000" port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol" redirectPort="8443"/>
客户端
我们利用Comet4J开发一个每隔一秒向所有客户端推送服务器的剩余内存大小。 helloworld.html
<!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="js/comet4j-0.0.2.js"></script>
<script type="text/javascript">
function init(){
var kbDom = document.getElementById('kb');
JS.Engine.on({
hello : function(kb){//侦听一个channel
kbDom.innerHTML = kb;
}
});
JS.Engine.start('conn');
}
</script>
</head>
<body onload="init()">
剩余内存：<span id="kb">...</span>KB
</body>
</html>
服务端
helloworld.java
package org.comet4j.demo.helloworld;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import org.comet4j.core.CometContext;
import org.comet4j.core.CometEngine;
public class HelloWorld implements ServletContextListener {
private static final String CHANNEL = "hello";
public void contextInitialized(ServletContextEvent arg0) {
CometContext cc = CometContext.getInstance();
cc.registChannel(CHANNEL);//注册应用的channel
Thread helloAppModule = new Thread(new HelloAppModule(), "Sender App Module");
helloAppModule.setDaemon(true);
helloAppModule.start();
}
class HelloAppModule implements Runnable {
public void run() {
while (true) {
try {
Thread.sleep(1000);
} catch (Exception ex) {
ex.printStackTrace();
}
CometEngine engine = CometContext.getInstance().getEngine();
engine.sendToAll(CHANNEL, Runtime.getRuntime().freeMemory()/1024);
}
}
}
public void contextDestroyed(ServletContextEvent arg0) {
}
}
配置
web.xml
<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>/conn</url-pattern> </servlet-mapping> <listener> <description>HelloWorld</description> <listener-class>org.comet4j.demo.helloworld.HelloWorld</listener-class> </listener>
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