對於頁面一直監控,以前都是使用ajax請求即可,但是小並發這做法沒多大問題,但是到了大並發就不太合適,如果不想自己寫線程來操控就可以偷懶找一些外掛程式,例如comet4j
下面我來示範下如何使用這個外掛程式
先準備需要的工具:
comet4j-tomcat6.jar(tomcat6的就匯入這個)
comet4j-tomcat7.jar(tomcat7的就匯入這個)
comet4j.js(頁面引入這個js)
具體操作看下面
然後就寫個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);// 註冊應用的channelcc.registChannel(CHANNEL2);Thread helloAppModule = new Thread(new HelloAppModule(),"Sender App Module");// 是否啟動helloAppModule.setDaemon(true);// 啟動線程helloAppModule.start();Thread helloAppModule2 = new Thread(new HelloAppModule2(),"Sender App Module");// 是否啟動helloAppModule2.setDaemon(true);// 啟動線程helloAppModule2.start();}class HelloAppModule2 implements Runnable {public void run() {while (true) {try {// 睡眠時間Thread.sleep(5000);} catch (Exception ex) {ex.printStackTrace();}CometEngine engine = CometContext.getInstance().getEngine();// 擷取訊息內容long l = getFreeMemory();// 開始發送engine.sendToAll(CHANNEL2, l);}}}class HelloAppModule implements Runnable {public void run() {while (true) {try {// 睡眠時間Thread.sleep(2000);} catch (Exception ex) {ex.printStackTrace();}CometEngine engine = CometContext.getInstance().getEngine();// 擷取訊息內容long l = getFreeMemory();// 開始發送engine.sendToAll(CHANNEL, l);}}}public void contextDestroyed(ServletContextEvent arg0) {}public long getFreeMemory() {return Runtime.getRuntime().freeMemory() / 1024;}}
然後再寫個頁面
<!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){//偵聽一個channel kbDom.innerHTML = aa; }, test2 : function(bb){ kbDom2.innerHTML = bb; } }); JS.Engine.start('comet');}</script></head><body onload="init()"> 剩餘記憶體：<span id="kb">...</span>KB <br/> 剩餘記憶體：<span id="kb2">...</span>KB</body></html>
接著配置下web.xml就ok了
<!-- comet4j --><listener><description>Comet4J容器偵聽</description><listener-class>org.comet4j.core.CometAppListener</listener-class></listener><servlet><description>Comet串連[預設: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>
最後修改下tomcat的server.xml檔案
把protocol參數值改成下面的,因為這是基於nio開發的外掛程式
<Connector URIEncoding="UTF-8" connectionTimeout="20000" port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol" redirectPort="8443"/>
測試,很簡單就是訪問我們剛剛建立的test.html,然後就可以看到記憶體數值一直自動重新整理波動
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