001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.servicemix.components.varscheduler;
018    
019    import java.util.TimerTask;
020    
021    /**
022     * A task run by a {@link Scheduler}.
023     * 
024     * @author George Gastaldi (gastaldi)
025     */
026    public abstract class SchedulerTask implements Runnable {
027    
028        static final int VIRGIN = 0;
029    
030        static final int SCHEDULED = 1;
031    
032        static final int CANCELLED = 2;
033    
034        final Object lock = new Object();
035    
036        int state = VIRGIN;
037    
038        TimerTask timerTask;
039    
040        protected SchedulerTask() {
041        }
042    
043        public abstract void run();
044    
045        /**
046         * Cancels task.
047         * 
048         * @return true if task already scheduled
049         */
050        public boolean cancel() {
051            synchronized (lock) {
052                if (timerTask != null) {
053                    timerTask.cancel();
054                }
055                boolean result = state == SCHEDULED;
056                state = CANCELLED;
057                return result;
058            }
059        }
060    
061        public long scheduledExecutionTime() {
062            synchronized (lock) {
063                return timerTask == null ? 0 : timerTask.scheduledExecutionTime();
064            }
065        }
066    
067    }