SchedulableRunnable.java |
/* * JBoss, the OpenSource J2EE webOS * * Distributable under LGPL license. * See terms of license at gnu.org. */ package org.jboss.mx.util; import EDU.oswego.cs.dl.util.concurrent.SynchronizedLong; /** * A schedulable runnable.<p> * * Subclasses should implement doRun() to do some real work.<p> * * setScheduler(RunnableScheduler) has to be invoked with a RunnableScheduler * that has been started for the work to be performed. If the doRun() does * not invoke setNextRun(), the link to the scheduler is removed. * * @see RunnableScheduler * * @author <a href="mailto:Adrian.Brock@HappeningTimes.com">Adrian Brock</a>. * @author Scott.Stark@jboss.org * @version $Revision: 1.3.6.2 $ */ public abstract class SchedulableRunnable implements Comparable, Runnable { // Attributes ---------------------------------------------------- /** * A unique identifier */ private long id; /** * The next run timestamp */ private SynchronizedLong nextRun = new SynchronizedLong(0); /** * The current scheduler */ private RunnableScheduler scheduler; /** * Whether we are running */ private boolean running; /** * Whether we should reschedule after the run */ private boolean reschedule; // Static -------------------------------------------------------- /** * The next unique identifier */ private static long nextId = 0; // Constructors -------------------------------------------------- /** * Constructs a new schedulable runnable. */ public SchedulableRunnable() { this.id = getNextId(); } // Public -------------------------------------------------------- /** * Gets the next run timestamp * * @return the next run */ public long getNextRun() { return nextRun.get(); } /** * Sets the next run date<p> * * If it is linked to a scheduler, it is temporarily removed while the date * is modified. * * @param nextRun the next run date */ public synchronized void setNextRun(long nextRun) { // Remove from scheduler if (scheduler != null) scheduler.remove(this); // Set the new run time this.nextRun.set(nextRun); // If we are not running, add it to the scheduler otherwise // remember we want adding back if (running == false && scheduler != null) { //log.debug("add to scheduler: " + this); scheduler.add(this); } else { //log.debug("reschedule: " + this); reschedule = true; } } /** * Set the scheduler for this runnable * * @param scheduler pass null to remove the runnable from any scheduler * @return the previous scheduler or null if there was no previous scheduler */ public synchronized RunnableScheduler setScheduler(RunnableScheduler scheduler) { // Null operation if (this.scheduler == scheduler) return this.scheduler; // Remember the result RunnableScheduler result = this.scheduler; // Remove from previous scheduler if (this.scheduler != null) this.scheduler.remove(this); // Set the new state this.scheduler = scheduler; // This is a remove operation if (scheduler == null) reschedule = false; // If we are not running, add it to the scheduler otherwise // remember we want adding else if (running == false) scheduler.add(this); else reschedule = true; // We are done return result; } /** * Do the work, the scheduled runnable should do its work here */ public abstract void doRun(); // Runnable Implementation --------------------------------------- /** * Runs doRun()<p> * * If setNextRun() is not invoked during the doRun(), the link to the * scheduler is removed */ public final void run() { startRun(); try { doRun(); } finally { endRun(); } } // Runnable Implementation --------------------------------------- public int compareTo(Object o) { SchedulableRunnable other = (SchedulableRunnable) o; long temp = this.nextRun.get() - other.nextRun.get(); if (temp < 0) return -1; if (temp > 0) return +1; temp = this.id - other.id; if (temp < 0) return -1; if (temp > 0) return +1; return 0; } // Object Overrides ---------------------------------------------- public boolean equals(Object obj) { return (compareTo(obj) == 0); } // Protected ----------------------------------------------------- // Package ------------------------------------------------------- // Private ------------------------------------------------------- /** * Start the run */ private synchronized void startRun() { running = true; } /** * Check whether the work got rescheduled */ private synchronized void endRun() { running = false; if (reschedule == true) scheduler.add(this); reschedule = false; } /** * Get the next identifier */ private static synchronized long getNextId() { return nextId++; } // Inner Classes ------------------------------------------------- }
SchedulableRunnable.java |