/*
* 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.util;
import java.util.Iterator ;
import org.apache.jena.atlas.iterator.Iter ;
import org.apache.jena.atlas.iterator.IteratorResourceClosing ;
import org.apache.jena.atlas.iterator.Transform ;
import org.apache.jena.atlas.lib.Closeable ;
import com.hp.hpl.jena.graph.Node ;
import com.hp.hpl.jena.graph.Triple ;
import com.hp.hpl.jena.query.QueryException ;
import com.hp.hpl.jena.rdf.model.Model ;
import com.hp.hpl.jena.rdf.model.RDFNode ;
import com.hp.hpl.jena.rdf.model.Statement ;
import com.hp.hpl.jena.rdf.model.StmtIterator;
import com.hp.hpl.jena.rdf.model.impl.LiteralImpl ;
import com.hp.hpl.jena.rdf.model.impl.ResourceImpl ;
import com.hp.hpl.jena.rdf.model.impl.StmtIteratorImpl ;
import com.hp.hpl.jena.sparql.ARQInternalErrorException ;
import com.hp.hpl.jena.util.iterator.ClosableIterator ;
public class ModelUtils
{
public static RDFNode convertGraphNodeToRDFNode(Node n, Model model)
{
if ( n.isVariable() )
throw new QueryException("Variable: "+n) ;
// Best way.
if ( model != null )
return model.asRDFNode(n) ;
if ( n.isLiteral() )
return new LiteralImpl(n, null) ;
if ( n.isURI() || n.isBlank() )
return new ResourceImpl(n, null) ;
throw new ARQInternalErrorException("Unknown node type for node: "+n) ;
}
public static Statement tripleToStatement(Model model, Triple t)
{
if ( model == null )
throw new ARQInternalErrorException("Attempt to create statement with null model") ;
Node sNode = t.getSubject() ;
Node pNode = t.getPredicate() ;
Node oNode = t.getObject() ;
if (!isValidAsStatement(sNode, pNode, oNode)) return null;
return model.asStatement(t) ;
}
/**
* Determines whether a valid Statement can be formed from the given Subject, Predicate and Object
* <p>
* This function reflects the fact that the {@link Triple} API is flexible in allowing any Node type in any position (including non-RDF node types like Variable)
* and as such not all Triples can be safely converted into Statements
* </p>
* @param s Subject
* @param p Predicate
* @param o Object
* @return True if a valid Statement can be formed
*/
public static boolean isValidAsStatement(Node s, Node p, Node o)
{
if ( s.isLiteral() || s.isVariable() )
return false ;
if ( ! p.isURI() ) // Not variable, literal or blank.
return false ;
if ( o.isVariable() )
return false ;
return true;
}
public static StmtIterator triplesToStatements(final Iterator<Triple> it, final Model refModel)
{
return new StmtIteratorImpl(Iter.map(it, new Transform<Triple,Statement>()
{
@Override
public Statement convert(Triple item)
{
return refModel.asStatement(item);
}
}))
{
// Make sure to close the incoming iterator
@Override
public void close()
{
if (it instanceof ClosableIterator<?>)
{
((ClosableIterator<?>)it).close();
}
else
{
Iter.close(it);
}
}
};
}
public static Iterator<Triple> statementsToTriples(final Iterator<Statement> it)
{
return new IteratorResourceClosing<Triple>(Iter.map(it, new Transform<Statement,Triple>()
{
@Override
public Triple convert(Statement item)
{
return item.asTriple();
}
}),
new Closeable()
{
@Override
public void close()
{
if (it instanceof ClosableIterator<?>)
{
((ClosableIterator<?>)it).close();
}
else
{
Iter.close(it);
}
}
});
}
}