主要包括如下几个类：
文章标题：java中基于TaskEngine类封装实现定时任务
文章地址: http://blog.****.net/5iasp/article/details/10950529
作者： javaboy2012
Email：yanek@163.com
qq: 1046011462
1. 核心工具类： TaskEngine
package com.yanek.task; import java.util.*;
import java.util.LinkedList; import org.apache.log4j.Logger; public class TaskEngine
{
static Logger logger = Logger.getLogger(TaskEngine.class.getName());
private static class PriorityQueue
{ public void enqueue(int priority, Object object)
{
if(priority > HIGH_PRIORITY)
priority = HIGH_PRIORITY;
else
if(priority < LOW_PRIORITY)
priority = LOW_PRIORITY;
switch(priority)
{
case HIGH_PRIORITY: // '\002'
high.addFirst(object);
break; case MEDIUM_PRIORITY: // '\001'
medium.addFirst(object);
break; case LOW_PRIORITY: // '\0'
low.addFirst(object);
break;
}
} public boolean isEmpty()
{
return high.isEmpty() && medium.isEmpty() && low.isEmpty();
} public int size()
{
return high.size() + medium.size() + low.size();
} public Object dequeue()
{
Object object;
if(!high.isEmpty())
object = high.removeLast();
else
if(!medium.isEmpty())
object = medium.removeLast();
else
if(!low.isEmpty())
object = low.removeLast();
else
throw new NoSuchElementException("Queue is empty.");
if(!low.isEmpty())
medium.addFirst(low.removeLast());
if(!medium.isEmpty())
high.addFirst(medium.removeLast());
return object;
} private LinkedList high;
private LinkedList medium;
private LinkedList low; private PriorityQueue()
{
high = new LinkedList();
medium = new LinkedList();
low = new LinkedList();
} } private static class ScheduledTask extends TimerTask
{ public void run()
{
TaskEngine.addTask(priority, task);
} private int priority;
private Runnable task; ScheduledTask(int priority, Runnable task)
{
this.priority = priority;
this.task = task;
}
} private static class TaskEngineWorker extends Thread
{ public void stopWorker()
{
done = true;
} public void run()
{
do
{
if(done)
break;
int currentThreadPriority = getPriority();
int newThreadPriority = currentThreadPriority;
try
{
TaskWrapper wrapper = TaskEngine.nextTask();
int desiredTaskPriority = wrapper.getPriority();
newThreadPriority = desiredTaskPriority != 2 ? ((int) (desiredTaskPriority != 1 ? 2 : 5)) : 9;
if(newThreadPriority != currentThreadPriority)
try
{
logger.debug("Running task engine worker (" + wrapper.getTask().getClass() + ") at thread priority " + newThreadPriority);
setPriority(newThreadPriority);
}
catch(Exception e)
{
logger.error(e);
}
logger.debug("Executing task (" + wrapper.getTask().getClass() + ")");
wrapper.getTask().run();
logger.debug("Completed execution task (" + wrapper.getTask().getClass() + ")");
if(newThreadPriority != currentThreadPriority)
try
{
logger.debug("Restoring task engine worker thread to thread priority - " + currentThreadPriority);
setPriority(currentThreadPriority);
}
catch(Exception e)
{
logger.error(e);
}
}
catch(Exception e)
{
logger.error(e);
if(newThreadPriority != currentThreadPriority)
try
{
logger.debug("Restoring task engine worker thread to thread priority - " + currentThreadPriority);
setPriority(currentThreadPriority);
}
catch(Exception e2)
{
logger.error(e2);
}
}
} while(true);
} private boolean done; TaskEngineWorker(String name)
{
super(TaskEngine.threadGroup, name);
done = false;
}
} private TaskEngine()
{
} public static void start()
{
synchronized(lock)
{
started = true;
lock.notifyAll();
}
} private static void initialize()
{
taskTimer = new Timer(true);
taskQueue = new PriorityQueue();
threadGroup = new ThreadGroup("Task Engine Workers");
workers = new TaskEngineWorker[5];
for(int i = 0; i < workers.length; i++)
{
workers[i] = new TaskEngineWorker("Task Engine Worker " + i);
workers[i].setDaemon(true);
workers[i].start();
} } public static int size()
{
synchronized(lock){
return taskQueue.size();
} } public static int getNumWorkers()
{
return workers.length;
} public static void addTask(Runnable task)
{
addTask(1, task);
} public static void addTask(int priority, Runnable task)
{
synchronized(lock)
{
if((double)taskQueue.size() > Math.ceil(workers.length / 2))
{
busyTimestamp = System.currentTimeMillis();
addWorker();
} else
if(workers.length > 3)
removeWorker();
TaskWrapper wrapper = new TaskWrapper(priority, task);
taskQueue.enqueue(priority, wrapper);
lock.notify();
}
} public static TimerTask scheduleTask(Runnable task, Date date)
{
return scheduleTask(1, task, date);
} public static TimerTask scheduleTask(int priority, Runnable task, Date date)
{
TimerTask timerTask = new ScheduledTask(priority, task);
taskTimer.schedule(timerTask, date);
return timerTask;
} //在1delay秒后执行此任务,每次间隔2秒period
public static TimerTask scheduleTask(Runnable task, long delay, long period)
{
return scheduleTask(1, task, delay, period);
} public static TimerTask scheduleTask(int priority, Runnable task, long delay, long period)
{
TimerTask timerTask = new ScheduledTask(priority, task);
taskTimer.scheduleAtFixedRate(timerTask, delay, period);
return timerTask;
} public static void shutdown()
{
taskTimer.cancel();
} public static void restart()
{
taskTimer.cancel();
initialize();
} private static TaskWrapper nextTask()
{
synchronized(lock){
while(taskQueue.isEmpty() || !started)
try
{
lock.wait();
}
catch(InterruptedException ie) { }
return (TaskWrapper)taskQueue.dequeue();
} } private static void addWorker()
{
if(workers.length < 30 && System.currentTimeMillis() > newWorkerTimestamp + 2000L)
{
int newSize = workers.length + 1;
int lastIndex = newSize - 1;
TaskEngineWorker newWorkers[] = new TaskEngineWorker[newSize];
System.arraycopy(workers, 0, newWorkers, 0, workers.length);
newWorkers[lastIndex] = new TaskEngineWorker("Task Engine Worker " + lastIndex);
newWorkers[lastIndex].setDaemon(true);
newWorkers[lastIndex].start();
workers = newWorkers;
newWorkerTimestamp = System.currentTimeMillis();
}
} private static void removeWorker()
{
if(workers.length > 3 && System.currentTimeMillis() > busyTimestamp + 5000L)
{
workers[workers.length - 1].stopWorker();
int newSize = workers.length - 1;
TaskEngineWorker newWorkers[] = new TaskEngineWorker[newSize];
System.arraycopy(workers, 0, newWorkers, 0, newSize);
workers = newWorkers;
busyTimestamp = System.currentTimeMillis();
}
} public static final int HIGH_PRIORITY = 2;
public static final int MEDIUM_PRIORITY = 1;
public static final int LOW_PRIORITY = 0;
private static PriorityQueue taskQueue = null;
private static ThreadGroup threadGroup;
private static TaskEngineWorker workers[] = null;
private static Timer taskTimer = null;
private static Object lock = new Object();
private static long newWorkerTimestamp = System.currentTimeMillis();
private static long busyTimestamp = System.currentTimeMillis();
private static boolean started = false; static
{
initialize();
} }
2. TaskWrapper 任务包装类
package com.yanek.task; public class TaskWrapper
{ public TaskWrapper(int priority, Runnable task)
{
this.priority = priority;
this.task = task;
} public Runnable getTask()
{
return task;
} public void setTask(Runnable task)
{
this.task = task;
} public int getPriority()
{
return priority;
} public void setPriority(int priority)
{
this.priority = priority;
} private Runnable task;
private int priority;
}
3. 测试任务类：
package com.yanek.task; import org.apache.log4j.Logger; //import com.aspboy.jxc.tcp.SocketClient; public class TestTask implements Runnable
{ static Logger Log = Logger.getLogger(TestTask.class.getName());
public void run()
{ System.out.println("time==="+System.currentTimeMillis());
} }
4. 监听器类： 启动时加载任务和启动任务
package com.yanek.task; import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener; public class TaskListener implements ServletContextListener { public static final long SECOND = 1000L; private ServletContext context; public TaskListener() {
System.out.println("LifeCycleListener new ... ");
} public void contextInitialized(ServletContextEvent event) { System.out.println("ServletContext Initialized... ");
context = event.getServletContext(); String prefix = event.getServletContext().getRealPath("/");
System.out.println("root path===" + prefix); TestTask testtask = new TestTask();
TaskEngine.scheduleTask(testtask, SECOND * 1, SECOND * 2);
TaskEngine.start(); } public void contextDestroyed(ServletContextEvent event) {
System.out.println("ServletContext Destroyed... ");
TaskEngine.shutdown();
} }
最后在web.xml配置监听器类：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <listener>
<listener-class>com.yanek.task.TaskListener</listener-class>
</listener> <welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
启动web容器，即可开始执行任务。