/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.camel.impl;
import java.util.Collection;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.camel.Service;
import org.apache.camel.ServiceStatus;
import org.apache.camel.util.ObjectHelper;
import org.apache.camel.util.ServiceHelper;
/**
* A useful base class which ensures that a service is only initialized once and
* provides some helper methods for enquiring of its status
*
* @version $Revision: 835732 $
*/
public abstract class ServiceSupport implements Service {
// TODO: refactor and move me to org.apache.camel.util package
private final AtomicBoolean started = new AtomicBoolean(false);
private final AtomicBoolean starting = new AtomicBoolean(false);
private final AtomicBoolean stopping = new AtomicBoolean(false);
private final AtomicBoolean stopped = new AtomicBoolean(false);
private Collection<Object> childServices;
private String version;
public void start() throws Exception {
if (!started.get()) {
if (starting.compareAndSet(false, true)) {
boolean childrenStarted = false;
Exception ex = null;
try {
if (childServices != null) {
ServiceHelper.startServices(childServices);
}
childrenStarted = true;
doStart();
} catch (Exception e) {
ex = e;
} finally {
if (ex != null) {
try {
stop(childrenStarted);
} catch (Exception e) {
// Ignore exceptions as we want to show the original exception
}
throw ex;
} else {
started.set(true);
starting.set(false);
stopping.set(false);
stopped.set(false);
}
}
}
}
}
private void stop(boolean childrenStarted) throws Exception {
if (stopping.compareAndSet(false, true)) {
try {
try {
starting.set(false);
if (childrenStarted) {
doStop();
}
} finally {
started.set(false);
if (childServices != null) {
ServiceHelper.stopServices(childServices);
}
}
} finally {
stopped.set(true);
stopping.set(false);
starting.set(false);
started.set(false);
}
}
}
public void stop() throws Exception {
if (started.get()) {
stop(true);
}
}
/**
* Returns the current status
*/
public ServiceStatus getStatus() {
// lets check these in oldest first as these flags can be changing in a concurrent world
if (isStarting()) {
return ServiceStatus.Starting;
}
if (isStarted()) {
return ServiceStatus.Started;
}
if (isStopping()) {
return ServiceStatus.Stopping;
}
if (isStopped()) {
return ServiceStatus.Stopped;
}
// use stopped as fallback
return ServiceStatus.Stopped;
}
/**
* @return true if this service has been started
*/
public boolean isStarted() {
return started.get();
}
/**
* @return true if this service is
*/
public boolean isStarting() {
return starting.get();
}
/**
* @return true if this service is in the process of closing
*/
public boolean isStopping() {
return stopping.get();
}
/**
* @return true if this service is closed
*/
public boolean isStopped() {
return stopped.get();
}
/**
* Helper methods so the service knows if it should keep running.
* Returns false if the service is being stopped or is stopped.
*
* @return true if the service should continue to run.
*/
public boolean isRunAllowed() {
return !(stopping.get() || stopped.get());
}
protected abstract void doStart() throws Exception;
protected abstract void doStop() throws Exception;
@SuppressWarnings("unchecked")
protected void addChildService(Object childService) {
synchronized (this) {
if (childServices == null) {
childServices = new CopyOnWriteArrayList();
}
}
childServices.add(childService);
}
protected boolean removeChildService(Object childService) {
return childServices != null && childServices.remove(childService);
}
/**
* Returns the version of this service
*/
public synchronized String getVersion() {
if (ObjectHelper.isNotEmpty(version)) {
return version;
}
Package aPackage = getClass().getPackage();
if (aPackage != null) {
version = aPackage.getImplementationVersion();
if (version == null) {
version = aPackage.getSpecificationVersion();
}
}
return version != null ? version : "";
}
}