/*
* 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.iterator;
import java.util.ArrayList ;
import java.util.List ;
import org.apache.jena.atlas.io.IndentedWriter ;
import com.hp.hpl.jena.sparql.engine.QueryIterator ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;
import com.hp.hpl.jena.sparql.serializer.SerializationContext ;
/** A caching QueryIterator. On demand, the application can ask for a new
* query iterator which will repeat the bindings yielded so far.
*/
public
class QueryIteratorCaching extends QueryIteratorWrapper
{
// Not tracked.
List<Binding> cache = new ArrayList<Binding>() ;
public QueryIteratorCaching(QueryIterator qIter)
{
super(qIter) ;
}
@Override
protected Binding moveToNextBinding()
{
Binding b = super.moveToNextBinding() ;
cache.add(b) ;
return b ;
}
@Override
public void output(IndentedWriter out, SerializationContext sCxt)
{}
public QueryIteratorCaching createRepeat()
{
List<Binding> elements = cache ;
if ( super.hasNext() )
// If the iterator isn't finished, copy what we have so far.
elements = new ArrayList<Binding>(cache) ;
return new QueryIteratorCaching(new QueryIterPlainWrapper(elements.iterator(), null)) ;
}
public static QueryIterator reset(QueryIterator qIter)
{
if ( qIter instanceof QueryIteratorCaching )
{
QueryIteratorCaching cIter = (QueryIteratorCaching)qIter ;
return cIter.createRepeat() ;
}
return qIter ;
}
}