/*
* 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 com.hp.hpl.jena.sparql.engine;
import org.apache.jena.atlas.io.IndentedWriter ;
import org.apache.jena.atlas.lib.Closeable ;
import com.hp.hpl.jena.sparql.ARQConstants ;
import com.hp.hpl.jena.sparql.ARQInternalErrorException ;
import com.hp.hpl.jena.sparql.algebra.Op ;
import com.hp.hpl.jena.sparql.serializer.SerializationContext ;
import com.hp.hpl.jena.sparql.util.PrintSerializableBase ;
public abstract class PlanBase extends PrintSerializableBase implements Plan
{
private Op op = null ;
protected Closeable closeable = null ;
protected boolean closed = false ;
private boolean iteratorProduced = false ;
protected abstract QueryIterator iteratorOnce() ;
protected PlanBase(Op op, Closeable closeable) { this.op = op ; this.closeable = closeable ; }
@Override
public Op getOp() { return op ; }
@Override
final
public QueryIterator iterator()
{
if ( iteratorProduced )
{
throw new ARQInternalErrorException("Attempt to use the iterator twice") ;
}
iteratorProduced = true ;
return iteratorOnce() ;
}
@Override
public void output(IndentedWriter out)
{
SerializationContext sCxt = new SerializationContext(ARQConstants.getGlobalPrefixMap()) ;
output(out, sCxt) ;
}
@Override
public void output(IndentedWriter out, SerializationContext sCxt)
{
op.output(out, sCxt) ;
}
@Override
public void close()
{
if ( closed )
return ;
if ( closeable != null )
// Called once
// Two routes - explicit QueryExecution.close
// or natural end of QueryIterator (see PlanOp)
closeable.close() ;
closed = true ;
}
}