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 */ 017package org.apache.activemq.util; 018 019import java.util.List; 020import java.util.concurrent.CopyOnWriteArrayList; 021import java.util.concurrent.atomic.AtomicBoolean; 022 023import org.apache.activemq.Service; 024import org.slf4j.Logger; 025import 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 */ 033public 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 preStart(); 055 doStart(); 056 success = true; 057 } finally { 058 started.set(success); 059 } 060 for(ServiceListener l:this.serviceListeners) { 061 l.started(this); 062 } 063 } 064 } 065 066 public void stop() throws Exception { 067 if (stopped.compareAndSet(false, true)) { 068 stopping.set(true); 069 ServiceStopper stopper = new ServiceStopper(); 070 try { 071 doStop(stopper); 072 } catch (Exception e) { 073 stopper.onException(this, e); 074 } finally { 075 postStop(stopper); 076 } 077 stopped.set(true); 078 started.set(false); 079 stopping.set(false); 080 for(ServiceListener l:this.serviceListeners) { 081 l.stopped(this); 082 } 083 stopper.throwFirstException(); 084 } 085 } 086 087 /** 088 * @return true if this service has been started 089 */ 090 public boolean isStarted() { 091 return started.get(); 092 } 093 094 /** 095 * @return true if this service is in the process of closing 096 */ 097 public boolean isStopping() { 098 return stopping.get(); 099 } 100 101 /** 102 * @return true if this service is closed 103 */ 104 public boolean isStopped() { 105 return stopped.get(); 106 } 107 108 public void addServiceListener(ServiceListener l) { 109 this.serviceListeners.add(l); 110 } 111 112 public void removeServiceListener(ServiceListener l) { 113 this.serviceListeners.remove(l); 114 } 115 116 /** 117 * 118 * handle for various operations after stopping the service (like locking) 119 * 120 * @throws Exception 121 */ 122 protected void postStop(ServiceStopper stopper) throws Exception {} 123 124 protected abstract void doStop(ServiceStopper stopper) throws Exception; 125 126 /** 127 * 128 * handle for various operations before starting the service (like locking) 129 * 130 * @throws Exception 131 */ 132 protected void preStart() throws Exception {} 133 134 protected abstract void doStart() throws Exception; 135}