Java tutorial
/** * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. * * @author Arne Kepp / The Open Planning Project 2008 */ package org.geowebcache.seed; import java.util.concurrent.atomic.AtomicInteger; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.geowebcache.GeoWebCacheException; /** * */ public abstract class GWCTask { private static final Log log = LogFactory.getLog(GWCTask.class); public static enum TYPE { UNSET, SEED, RESEED, TRUNCATE }; public static enum STATE { UNSET, READY, RUNNING, DONE, DEAD }; /** * Value shared between all the threads in the group, is incremented each time a task starts * working and decremented each time one task finishes (either normally or abnormally) */ protected AtomicInteger sharedThreadCount = new AtomicInteger(); protected int threadOffset = 0; long taskId = -1; protected TYPE parsedType = TYPE.UNSET; protected STATE state = STATE.UNSET; protected String layerName = null; protected long timeSpent = -1; protected long timeRemaining = -1; protected long tilesDone = -1; protected long tilesTotal = -1; protected boolean terminate = false; private long groupStartTime; /** * Marks this task as active in the group by incrementing the shared counter, delegates to * {@link #doActionInternal()}, and makes sure to remove this task from the group count. */ public final void doAction() throws GeoWebCacheException, InterruptedException { this.sharedThreadCount.incrementAndGet(); this.groupStartTime = System.currentTimeMillis(); try { doActionInternal(); } finally { dispose(); int membersRemaining = this.sharedThreadCount.decrementAndGet(); if (0 == membersRemaining) { double groupTotalTimeSecs = (System.currentTimeMillis() - (double) groupStartTime) / 1000; log.info("Thread group finished " + parsedType + " task after " + groupTotalTimeSecs + " seconds"); } } } protected abstract void dispose(); /** * Extension point for subclasses to do what they do */ protected abstract void doActionInternal() throws GeoWebCacheException, InterruptedException; /** * @param sharedThreadCount * a counter of number of active tasks in the task group, incremented when this task * starts working and decremented when it stops * @param threadOffset * REVISIT: may not be needed anymore. Just check if sharedThreadCount == 1? */ public void setThreadInfo(AtomicInteger sharedThreadCount, int threadOffset) { this.sharedThreadCount = sharedThreadCount; this.threadOffset = threadOffset; } public void setTaskId(long taskId) { this.taskId = taskId; } public long getTaskId() { return taskId; } public int getThreadCount() { return sharedThreadCount.get(); } public int getThreadOffset() { return threadOffset; } public String getLayerName() { return layerName; } /** * @return total number of tiles (in the whole task group), or < 0 if too many to count */ public long getTilesTotal() { return tilesTotal; } public long getTilesDone() { return tilesDone; } /** * @return estimated remaining time in seconds, or {@code -2} if unknown */ public long getTimeRemaining() { if (tilesTotal > 0) { return timeRemaining; } else { return -2; } } /** * @return task time spent in seconds */ public long getTimeSpent() { return timeSpent; } public void terminateNicely() { this.terminate = true; } public TYPE getType() { return parsedType; } public STATE getState() { return state; } protected void checkInterrupted() throws InterruptedException { if (Thread.interrupted()) { this.state = STATE.DEAD; throw new InterruptedException(); } } @Override public String toString() { return new StringBuilder("[").append(getTaskId()).append(": ").append(getLayerName()).append(", ") .append(getType()).append(", ").append(getState()).append("]").toString(); } }