Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. */ package com.jhkt.playgroundArena.shared.tasks.common; import java.util.Collection; import java.util.PriorityQueue; import java.util.Queue; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.FutureTask; import java.util.concurrent.TimeUnit; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * @author Ji Hoon Kim */ public final class TaskQueues { private static final String DUPLICATE_QUEUE_TASK_ID_PROVIDED = "Duplicate future queue task id has been provided : "; private static final int EXECUTOR_SERVICE_SHUT_DOWN_LIMIT = 20; private final static TaskQueues _instance = new TaskQueues(); private final static Log _log = LogFactory.getLog(TaskQueues.class); public enum QUEUE_TASK_ID { CHMOD, COMMAND, DELETE, ECHO, FILE_COPY, MKDIR, RENAME, REPLACE_TEXT, UNZIP_ARCHIVE_RELATIVE, UNZIP_ARCHIVE_ABSOLUTE_FI, UNZIP_ARCHIVE_ABSOLUTE_IS; public String getQueueTaskId(String queueTaskId) { return toString() + ":" + queueTaskId; } } private final ExecutorService _queuedService; private final ConcurrentMap<String, Future<Void>> _queuedTasks; private final Object _lock = new Object(); private final Queue<AbstractTask> _tasks; private TaskQueues() { super(); } { _queuedService = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors() * 2); _queuedTasks = new ConcurrentHashMap<String, Future<Void>>(); _tasks = new PriorityQueue<AbstractTask>(); } public static TaskQueues getInstance() { return _instance; } public void addTask(AbstractTask toAdd) { synchronized (_lock) { _tasks.add(toAdd); execute(); } } public void addTasks(Collection<AbstractTask> tasksToAdd) { synchronized (_lock) { _tasks.addAll(tasksToAdd); execute(); } } public void execute() { synchronized (_lock) { for (AbstractTask current : _tasks) { current.performTask(); } clearAllTask(); } } private void clearAllTask() { _tasks.clear(); } /* * Though finalize method is not always invoked, place in the code to clean * up ExecutorService for times when it is called. */ @Override protected void finalize() throws Throwable { super.finalize(); if (_queuedService != null) { _queuedService.shutdownNow(); } if (_queuedTasks != null) { _queuedTasks.clear(); } } public void queueFutureTask(final String taskName, final AbstractTask toAdd) { final FutureTask<Void> task = new FutureTask<Void>(new Runnable() { public void run() { toAdd.performTask(); _queuedTasks.remove(taskName); _log.info("Queued taskName has been completed : " + taskName); } }, null); Future<Void> previousTask = _queuedTasks.putIfAbsent(taskName, task); if (previousTask != null) { throw new RuntimeException(DUPLICATE_QUEUE_TASK_ID_PROVIDED + taskName); } _queuedService.submit(task); } public void cancelQueuedFutureTask(String taskName) { Future<Void> task = _queuedTasks.get(taskName); task.cancel(true); _queuedTasks.remove(taskName); } public boolean isTaskDone(String taskName) { Future<Void> task = _queuedTasks.get(taskName); return (task != null && task.isDone()); } public void waitForFutureTask(String taskName) { Future<Void> task = _queuedTasks.get(taskName); if (task != null) { try { _log.info("Waiting for taskName : " + taskName); task.get(); _log.info("Finished waiting for the taskName : " + taskName); } catch (ExecutionException executeExcept) { _log.error("Execution exception thrown within waitForFutureTask for " + taskName, executeExcept); } catch (InterruptedException interruptedExcept) { Thread.currentThread().interrupt(); } finally { task.cancel(true); } } } public void checkTaskEntrySizeAndShutDown() { if (_queuedTasks != null && _queuedTasks.size() == 0) { clearAllFutureTasks(); } } public void clearAllFutureTasks() { _queuedService.shutdown(); try { _queuedService.awaitTermination(EXECUTOR_SERVICE_SHUT_DOWN_LIMIT, TimeUnit.SECONDS); } catch (InterruptedException interruptedException) { Thread.currentThread().interrupt(); } finally { if (_queuedTasks != null) { _queuedTasks.clear(); } } } }