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.activemq.util;
018
019 import java.util.List;
020 import java.util.concurrent.CopyOnWriteArrayList;
021 import java.util.concurrent.atomic.AtomicBoolean;
022
023 import org.apache.activemq.Service;
024 import org.slf4j.Logger;
025 import org.slf4j.LoggerFactory;
026
027 /**
028 * A helper class for working with services together with a useful base class
029 * for service implementations.
030 *
031 *
032 */
033 public abstract class ServiceSupport implements Service {
034 private static final Logger LOG = LoggerFactory.getLogger(ServiceSupport.class);
035
036 private AtomicBoolean started = new AtomicBoolean(false);
037 private AtomicBoolean stopping = new AtomicBoolean(false);
038 private AtomicBoolean stopped = new AtomicBoolean(false);
039 private List<ServiceListener>serviceListeners = new CopyOnWriteArrayList<ServiceListener>();
040
041 public static void dispose(Service service) {
042 try {
043 service.stop();
044 } catch (Exception e) {
045 LOG.debug("Could not stop service: " + service + ". Reason: " + e, e);
046 }
047 }
048
049 public void start() throws Exception {
050 if (started.compareAndSet(false, true)) {
051 boolean success = false;
052 stopped.set(false);
053 try {
054 doStart();
055 success = true;
056 } finally {
057 started.set(success);
058 }
059 for(ServiceListener l:this.serviceListeners) {
060 l.started(this);
061 }
062 }
063 }
064
065 public void stop() throws Exception {
066 if (stopped.compareAndSet(false, true)) {
067 stopping.set(true);
068 ServiceStopper stopper = new ServiceStopper();
069 try {
070 doStop(stopper);
071 } catch (Exception e) {
072 stopper.onException(this, e);
073 }
074 stopped.set(true);
075 started.set(false);
076 stopping.set(false);
077 for(ServiceListener l:this.serviceListeners) {
078 l.stopped(this);
079 }
080 stopper.throwFirstException();
081 }
082 }
083
084 /**
085 * @return true if this service has been started
086 */
087 public boolean isStarted() {
088 return started.get();
089 }
090
091 /**
092 * @return true if this service is in the process of closing
093 */
094 public boolean isStopping() {
095 return stopping.get();
096 }
097
098 /**
099 * @return true if this service is closed
100 */
101 public boolean isStopped() {
102 return stopped.get();
103 }
104
105 public void addServiceListener(ServiceListener l) {
106 this.serviceListeners.add(l);
107 }
108
109 public void removeServiceListener(ServiceListener l) {
110 this.serviceListeners.remove(l);
111 }
112
113 protected abstract void doStop(ServiceStopper stopper) throws Exception;
114
115 protected abstract void doStart() throws Exception;
116 }