/**
* Copyright (c) 2002-2010 "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 Affero 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.index.impl;
import java.util.Iterator;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.NotFoundException;
import org.neo4j.helpers.collection.PrefetchingIterator;
/**
* Converts an Iterator<Long> of node ids to an Iterator<Node> where the
* {@link GraphDatabaseService#getNodeById(long)} is used to look up the nodes,
* one call per step in the iterator.
*/
public class IdToNodeIterator extends PrefetchingIterator<Node>
{
private final Iterator<Long> ids;
private final GraphDatabaseService graphDb;
/**
* @param ids the node ids to use as underlying iterator.
* @param graphDb the {@link GraphDatabaseService} to use for node lookups.
*/
public IdToNodeIterator( Iterator<Long> ids, GraphDatabaseService graphDb )
{
this.ids = ids;
this.graphDb = graphDb;
}
@Override
protected Node fetchNextOrNull()
{
Node result = null;
while ( result == null )
{
if ( !ids.hasNext() )
{
return null;
}
long id = ids.next();
try
{
return graphDb.getNodeById( id );
}
catch ( NotFoundException e )
{
// Rare exception which can occur under normal
// circumstances
}
}
return result;
}
}