Java tutorial
/* * Copyright (c) 2016, WSO2 Inc. (http://www.wso2.org) All Rights Reserved. * * WSO2 Inc. 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 org.wso2.carbon.bpmn.people.substitution.scheduler; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.wso2.carbon.bpmn.core.BPMNConstants; import org.wso2.carbon.bpmn.people.substitution.UserSubstitutionUtils; import java.util.concurrent.Callable; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; public class SubstitutionScheduler implements ScheduledTaskRunner { private static Log log = LogFactory.getLog(SubstitutionScheduler.class); private SchedulerThread _todo; private boolean _running; ExecutorService _exec; /** * Jobs scheduled with a time that is between [now, now+immediateInterval] will be assigned to the current node, and placed * directly on the todo queue. */ long interval = BPMNConstants.DEFAULT_SUBSTITUTION_INTERVAL_IN_MINUTES * 60 * 1000; public SubstitutionScheduler(long interval) { _todo = new SchedulerThread(this); this.interval = interval; } @Override public void runTask(final ScheduledTask task) { Future future = _exec.submit(new Callable<Void>() { public Void call() throws Exception { try { ((SchedulerScheduledTask) task).run(); } catch (Exception ex) { log.error("Error during scheduled task execution for substitutes", ex); } return null; } }); if (log.isDebugEnabled()) { log.debug("Scheduled task : " + task.toString() + ", completed : " + future.isDone()); } } public synchronized void start() { if (_running) return; if (_exec == null) { _exec = Executors.newCachedThreadPool(); } _todo.enqueue(new LoadImmediateScheduledTask(System.currentTimeMillis())); _todo.start(); _running = true; } public synchronized void stop() { if (!_running) return; _todo.stop(); _todo.clearTasks(LoadImmediateScheduledTask.class); _running = false; } private abstract class SchedulerScheduledTask extends ScheduledTask implements Runnable { SchedulerScheduledTask(long schedDate) { super(schedDate); } } private class LoadImmediateScheduledTask extends SchedulerScheduledTask { LoadImmediateScheduledTask(long schedDate) { super(schedDate); } public void run() { boolean success = false; try { log.debug("Executing BPMN User Substitution scheduled event"); success = UserSubstitutionUtils.handleScheduledEvent(); } finally { if (success) { _todo.enqueue(new LoadImmediateScheduledTask(System.currentTimeMillis() + (long) (interval))); } else { log.debug("BPMN User Substitution scheduled event failed. Scheduling next event in 60 seconds"); _todo.enqueue(new LoadImmediateScheduledTask(System.currentTimeMillis() + 1000 * 60)); } } } } /** * Get the remaining time for the next scheduled event. * @return remaining time in milliseconds, very big number of no scheduled event */ public long getNextScheduledTime() { return _todo.nextJobTime(); } }