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DataSourceManager.java
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DataSourceManager.java
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/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.impl.transaction.state;
import java.util.function.Supplier;
import org.neo4j.graphdb.DependencyResolver;
import org.neo4j.helpers.Listeners;
import org.neo4j.kernel.NeoStoreDataSource;
import org.neo4j.kernel.api.KernelAPI;
import org.neo4j.kernel.lifecycle.LifeSupport;
import org.neo4j.kernel.lifecycle.Lifecycle;
import org.neo4j.kernel.lifecycle.LifecycleStatus;
/**
* Adds change listener features to a {@link NeoStoreDataSource}.
* <p/>
* TODO This being a {@link KernelAPI} {@link Supplier} is a smell, it comes from established bad dependency hierarchy
* where {@link NeoStoreDataSource} and {@link KernelAPI} are needed before they exist.
*/
public class DataSourceManager implements Lifecycle, Supplier<KernelAPI>
{
public interface Listener
{
void registered( NeoStoreDataSource dataSource );
void unregistered( NeoStoreDataSource dataSource );
}
private LifeSupport life = new LifeSupport();
private final Listeners<Listener> dsRegistrationListeners = new Listeners<>();
private NeoStoreDataSource dataSource;
public void addListener( Listener listener )
{
if ( life.getStatus().equals( LifecycleStatus.STARTED ) )
{
try
{
if ( dataSource != null )
{
listener.registered( dataSource );
}
}
catch ( Throwable t )
{ // OK
}
}
dsRegistrationListeners.add( listener );
}
public void register( NeoStoreDataSource dataSource )
{
this.dataSource = dataSource;
if ( life.getStatus().equals( LifecycleStatus.STARTED ) )
{
dsRegistrationListeners.notify( listener -> listener.registered( dataSource ) );
}
}
public void unregister( NeoStoreDataSource dataSource )
{
this.dataSource = null;
dsRegistrationListeners.notify( listener -> listener.unregistered( dataSource ) );
life.remove( dataSource );
}
public NeoStoreDataSource getDataSource()
{
return dataSource;
}
@Override
public void init() throws Throwable
{
life = new LifeSupport();
life.add( dataSource );
}
@Override
public void start() throws Throwable
{
life.start();
for ( Listener listener : dsRegistrationListeners )
{
try
{
if ( dataSource != null )
{
listener.registered( dataSource );
}
}
catch ( Throwable t )
{ // OK
}
}
}
@Override
public void stop() throws Throwable
{
life.stop();
}
@Override
public void shutdown() throws Throwable
{
life.shutdown();
dataSource = null;
}
@Override
public KernelAPI get()
{
return dataSource.getKernel();
}
public static class DependencyResolverSupplier implements Supplier<DependencyResolver>
{
private DataSourceManager dataSourceManager;
public DependencyResolverSupplier( DataSourceManager dataSourceManager )
{
this.dataSourceManager = dataSourceManager;
}
@Override
public DependencyResolver get()
{
NeoStoreDataSource dataSource = dataSourceManager.getDataSource();
if ( dataSource == null )
{
return null;
}
return dataSource.getDependencyResolver();
}
}
}