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 try {
053 doStart();
054 success = true;
055 } finally {
056 started.set(success);
057 }
058 for(ServiceListener l:this.serviceListeners) {
059 l.started(this);
060 }
061 }
062 }
063
064 public void stop() throws Exception {
065 if (stopped.compareAndSet(false, true)) {
066 stopping.set(true);
067 ServiceStopper stopper = new ServiceStopper();
068 try {
069 doStop(stopper);
070 } catch (Exception e) {
071 stopper.onException(this, e);
072 }
073 stopped.set(true);
074 started.set(false);
075 stopping.set(false);
076 for(ServiceListener l:this.serviceListeners) {
077 l.stopped(this);
078 }
079 stopper.throwFirstException();
080 }
081 }
082
083 /**
084 * @return true if this service has been started
085 */
086 public boolean isStarted() {
087 return started.get();
088 }
089
090 /**
091 * @return true if this service is in the process of closing
092 */
093 public boolean isStopping() {
094 return stopping.get();
095 }
096
097 /**
098 * @return true if this service is closed
099 */
100 public boolean isStopped() {
101 return stopped.get();
102 }
103
104 public void addServiceListener(ServiceListener l) {
105 this.serviceListeners.add(l);
106 }
107
108 public void removeServiceListener(ServiceListener l) {
109 this.serviceListeners.remove(l);
110 }
111
112 protected abstract void doStop(ServiceStopper stopper) throws Exception;
113
114 protected abstract void doStart() throws Exception;
115 }