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/*
* Copyright (C) 2009 The Guava Authors
*
* Licensed 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 com.google.common.util.concurrent;
import com.google.common.annotations.Beta;
import com.google.common.base.Throwables;
import java.util.concurrent.Executor;
/**
* Base class for services that do not need a thread while "running"
* but may need one during startup and shutdown. Subclasses can
* implement {@link #startUp} and {@link #shutDown} methods, each
* which run in a executor which by default uses a separate thread
* for each method.
*
* @author Chris Nokleberg
* @since 1.0
*/
@Beta
public abstract class AbstractIdleService implements Service {
/* use AbstractService for state management */
private final Service delegate = new AbstractService() {
@Override protected final void doStart() {
executor(State.STARTING).execute(new Runnable() {
@Override public void run() {
try {
startUp();
notifyStarted();
} catch (Throwable t) {
notifyFailed(t);
throw Throwables.propagate(t);
}
}
});
}
@Override protected final void doStop() {
executor(State.STOPPING).execute(new Runnable() {
@Override public void run() {
try {
shutDown();
notifyStopped();
} catch (Throwable t) {
notifyFailed(t);
throw Throwables.propagate(t);
}
}
});
}
};
/** Start the service. */
protected abstract void startUp() throws Exception;
/** Stop the service. */
protected abstract void shutDown() throws Exception;
/**
* Returns the {@link Executor} that will be used to run this service.
* Subclasses may override this method to use a custom {@link Executor}, which
* may configure its worker thread with a specific name, thread group or
* priority. The returned executor's {@link Executor#execute(Runnable)
* execute()} method is called when this service is started and stopped,
* and should return promptly.
*
* @param state {@link Service.State#STARTING} or
* {@link Service.State#STOPPING}, used by the default implementation for
* naming the thread
*/
protected Executor executor(final State state) {
return new Executor() {
@Override
public void execute(Runnable command) {
new Thread(command, getServiceName() + " " + state).start();
}
};
}
@Override public String toString() {
return getServiceName() + " [" + state() + "]";
}
// We override instead of using ForwardingService so that these can be final.
@Override public final ListenableFuture<State> start() {
return delegate.start();
}
@Override public final State startAndWait() {
return delegate.startAndWait();
}
@Override public final boolean isRunning() {
return delegate.isRunning();
}
@Override public final State state() {
return delegate.state();
}
@Override public final ListenableFuture<State> stop() {
return delegate.stop();
}
@Override public final State stopAndWait() {
return delegate.stopAndWait();
}
@Override public final void addListener(Listener listener, Executor executor) {
delegate.addListener(listener, executor);
}
private String getServiceName() {
return getClass().getSimpleName();
}
}
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