java中基于TaskEngine类封装实现定时任务

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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.csdn.net/5iasp/article/details/10950529 作者: javaboy2012 Email:[email protected] 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。  

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