如何使用Timer Service

Gary Niu — Mon, 31 Jul 2006 05:13:00 GMT

　　 如何使用Timer Service
作者：牛秀元

WebLogic Server 包含了 Timer Service 功能，你可以指定某一时刻或某一时间间隔产生 Timer 事件，同时你可以使用委托代理的机制，为这个事件注册事件监听器，以实现 Timer Service 功能。

　　从 WebLogic Server 7.0 以后的版本， WebLogic Timer Service 扩展自标准的 JMX Timer Service ，使其可以运行于 WebLogic Server 的执行线程中，并且享有 WebLogic Server 的安全上下文环境，也就是说，可以在代码中得到安全信息，如用户名等。下面结合一个实例演示其功能。

File:TimerServiceListener.java

package org.yekki.weblogic.timer;

import java.util.Date;

import java.util.Random;

import javax.jms.JMSException;

import javax.jms.Queue;

import javax.jms.QueueConnection;

import javax.jms.QueueConnectionFactory;

import javax.jms.QueueSender;

import javax.jms.QueueSession;

import javax.jms.Session;

import javax.jms.TextMessage;

import javax.management.InstanceNotFoundException;

import javax.management.Notification;

import javax.management.NotificationListener;

import javax.naming.Context;

import javax.naming.InitialContext;

import javax.servlet.ServletContext;

import javax.servlet.ServletContextEvent;

import javax.servlet.ServletContextListener;

import org.apache.ecs.xml.XML;

import weblogic.management.timer.Timer;

public class TimerServiceListener

implements ServletContextListener, NotificationListener {

private long period;

private boolean debug;

private Timer timer;

private Integer notificationId;

private QueueConnectionFactory factory;

private QueueConnection connection;

private QueueSession session;

private QueueSender sender;

private Queue queue;

private Context ctx;

public void contextInitialized(ServletContextEvent event) {

initParams(event);

initJMS();

debug(">>> contextInitialized called.");

timer = new Timer();

timer.addNotificationListener(this, null, "Message Broker ");

Date timerTriggerAt = new Date((new Date()).getTime() + 5000L);

notificationId =

timer.addNotification(

"Timer Type",

"Timer Message",

this,

timerTriggerAt,

period);

timer.start();

debug(">>> timer started.");

printBrief();

}

public void initParams(ServletContextEvent event) {

ServletContext ctx = event.getServletContext();

try {

debug = Boolean.valueOf((String)ctx.getInitParameter("debug")).booleanValue();

}

catch (Exception e) {

debug = false;

e.printStackTrace();

}

try {

second:1000L

minute:60000L

hour:3600000L

day:86400000L

week:604800000L

period =

Long

.valueOf((String)ctx.getInitParameter("period"))

.longValue();

}

catch (Exception e) {

period = Timer.ONE_MINUTE;

e.printStackTrace();

}

debug(">>> initialized application parameters.");

}

private void initJMS() {

try {

ctx = new InitialContext();

factory =

(QueueConnectionFactory)ctx.lookup(

"javax.jms.QueueConnectionFactory");

queue = (Queue)ctx.lookup("queue");

connection = factory.createQueueConnection();

session =

connection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);

sender = session.createSender(queue);

connection.start();

debug(">>> initialized jms.");

}

catch (Exception e) {

e.printStackTrace();

}

public void sendMessage(String message) {

try {

TextMessage msg = session.createTextMessage();

msg.setText(message);

sender.send(msg);

debug(">>> ################################");

debug("Send a message on " + new Date());

debug(message);

debug(">>> ################################");

}

catch (JMSException e) {

e.printStackTrace();

}

public void contextDestroyed(ServletContextEvent event) {

debug(">>> contextDestroyed called.");

try {

timer.stop();

timer.removeNotification(notificationId);

debug(">>> timer stopped.");

}

catch (InstanceNotFoundException e) {

e.printStackTrace();

}

try {

if (session != null)

session.close();

if (connection != null)

connection.close();

debug(">>> closed jms connection and session.");

}

catch (JMSException e) {

e.printStackTrace();

}

private void printBrief() {

String d = "";

d = debug ? "ON" : "OFF";

print(">>> ################################");

print(">>> Author: Niu Xiuyuan");

print(">>> EMail: niuxiuyuan@bea.com.cn");

print(">>> Company: BEA Systems");

print("");

print(">>> Debug: " + d);

print(">>> Period: " + getPeriodInfo(period));

print(">>> ################################");

}

private void print(String str) {

System.out.println(str);

}

private String getPeriodInfo(long p) {

if (p == Timer.ONE_DAY)

return "One Day";

if (p == Timer.ONE_HOUR)

return "One Hour";

if (p == Timer.ONE_MINUTE)

return "One Minute";

if (p == Timer.ONE_SECOND)

return "One Second";

if (p == Timer.ONE_WEEK)

return "One Week";

return "Unsupported time period!! period=" + p;

}

public void handleNotification(Notification notif, Object handback) {

Random rnd = new Random();

sendMessage(genXML(rnd.nextInt(10)));

}

public String genXML(int id) {

String username = "guru";

String password = "niu986";

XML usernameXML = null;

XML idXML = null;

XML passwordXML = null;

XML userXML = null;

XML profileXML = new XML("profiles");

for (int i = 1; i <= id; i++) {

usernameXML = (new XML("user")).addElement(username);

idXML = (new XML("id")).addElement(Integer.toString(id));

passwordXML = (new XML("password")).addElement(password);

userXML =

(new XML("user"))

.addXMLAttribute("age", "27")

.addElement(idXML)

.addElement(usernameXML)

.addElement(passwordXML);

profileXML.addElement(userXML);

}

return profileXML.toString();

}

private void debug(String msg) {

if (debug) {

System.out.println(msg);

}

public static void main(String[] args) {

}

　　说明：为了方便演示，此类中包含了事件产生器代码与事件监听器代码。使用 ServletContextListener 接口来控制 Timer 的启动与停止。

File:web.xml

debug

false

period

60000

org.yekki.weblogic.timer.TimerServiceListener

　　说明：我们将 webapp 的 Lisener 注册，并且指定事件产生的时间间隔

将此 WebApp 部署到 WebLogic Server 上，然后通过中端（例如： DOS 窗口）查看实验结果。

　　附：本例中使用了 Apache 的 ECS 项目类库，您可以访问如下 URL:

　　http://jakarta.apache.org/ecs/index.html

Gary Niu 2006-07-31 13:13 发表评论

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如何使用Timer Service