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.camel.impl;
018    
019    import java.util.ArrayList;
020    import java.util.Collection;
021    import java.util.concurrent.atomic.AtomicBoolean;
022    
023    import org.apache.camel.Service;
024    import org.apache.camel.util.ServiceHelper;
025    
026    /**
027     * A useful base class which ensures that a service is only initialized once and
028     * provides some helper methods for enquiring of its status
029     *
030     * @version $Revision: 41776 $
031     */
032    public abstract class ServiceSupport implements Service {
033        private static int threadCounter;
034        private AtomicBoolean started = new AtomicBoolean(false);
035        private AtomicBoolean starting = new AtomicBoolean(false);
036        private AtomicBoolean stopping = new AtomicBoolean(false);
037        private AtomicBoolean stopped = new AtomicBoolean(false);
038        private Collection childServices;
039    
040        public void start() throws Exception {
041            if (started.compareAndSet(false, true)) {
042                starting.set(true);
043                try {
044                    if (childServices != null) {
045                        ServiceHelper.startServices(childServices);
046                    }
047                    doStart();
048                } finally {
049                    starting.set(false);
050                }
051            }
052        }
053    
054        public void stop() throws Exception {
055            if (started.get() && stopping.compareAndSet(false, true)) {
056                try {
057                    doStop();
058                } finally {
059                    if (childServices != null) {
060                        ServiceHelper.stopServices(childServices);
061                    }
062                    stopped.set(true);
063                    started.set(false);
064                    stopping.set(false);
065                }
066            }
067        }
068    
069        /**
070         * @return true if this service has been started
071         */
072        public boolean isStarted() {
073            return started.get();
074        }
075    
076        /**
077         * @return true if this service is
078         */
079        public boolean isStarting() {
080            return starting.get();
081        }
082    
083        /**
084         * @return true if this service is in the process of closing
085         */
086        public boolean isStopping() {
087            return stopping.get();
088        }
089    
090        /**
091         * Helper methods so the service knows if it should keep running.
092         * Returns false if the service is being stopped or is stopped.
093         *
094         * @return true if the service should continue to run.
095         */
096        protected boolean isRunAllowed() {
097            return !(stopping.get() || stopped.get());
098        }
099    
100        /**
101         * @return true if this service is closed
102         */
103        public boolean isStopped() {
104            return stopped.get();
105        }
106    
107        protected abstract void doStart() throws Exception;
108    
109        protected abstract void doStop() throws Exception;
110    
111        /**
112         * Creates a new thread name with the given prefix
113         */
114        protected String getThreadName(String prefix) {
115            return prefix + " thread:" + nextThreadCounter();
116        }
117    
118        protected static synchronized int nextThreadCounter() {
119            return ++threadCounter;
120        }
121    
122        protected void addChildService(Object childService) {
123            if (childServices == null) {
124                childServices = new ArrayList();
125            }
126            childServices.add(childService);
127        }
128    
129        protected boolean removeChildService(Object childService) {
130            if (childServices != null) {
131                return childServices.remove(childService);
132            } else {
133                return false;
134            }
135        }
136    }