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* 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 arq.examples;
import java.util.ArrayList ;
import java.util.List ;
import org.apache.jena.datatypes.xsd.XSDDatatype ;
import org.apache.jena.graph.Node ;
import org.apache.jena.graph.NodeFactory ;
import org.apache.jena.graph.Triple ;
import org.apache.jena.query.ResultSet ;
import org.apache.jena.query.ResultSetFormatter ;
import org.apache.jena.rdf.model.* ;
import org.apache.jena.riot.out.NodeFmtLib ;
import org.apache.jena.sparql.algebra.Algebra ;
import org.apache.jena.sparql.algebra.Op ;
import org.apache.jena.sparql.algebra.op.OpBGP ;
import org.apache.jena.sparql.algebra.op.OpFilter ;
import org.apache.jena.sparql.core.BasicPattern ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.ResultSetStream ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.expr.E_LessThan ;
import org.apache.jena.sparql.expr.Expr ;
import org.apache.jena.sparql.expr.ExprVar ;
import org.apache.jena.sparql.expr.NodeValue ;
/** Build an algebra expression and execute it */
public class AlgebraExec
{
public static void main (String[] argv)
{
String BASE = "http://example/" ;
BasicPattern bp = new BasicPattern() ;
Var var_x = Var.alloc("x") ;
Var var_z = Var.alloc("z") ;
// ---- Build expression
bp.add(new Triple(var_x, NodeFactory.createURI(BASE+"p"), var_z)) ;
Op op = new OpBGP(bp) ;
//Expr expr = ExprUtils.parse("?z < 2 ") ;
Expr expr = new E_LessThan(new ExprVar(var_z), NodeValue.makeNodeInteger(2)) ;
op = OpFilter.filter(expr, op) ;
// ---- Example setup
Model m = makeModel() ;
m.write(System.out, "TTL") ;
System.out.println("--------------") ;
System.out.print(op) ;
System.out.println("--------------") ;
// ---- Execute expression
QueryIterator qIter = Algebra.exec(op, m.getGraph()) ;
// -------- Either read the query iterator directly ...
if ( false )
{
for ( ; qIter.hasNext() ; )
{
Binding b = qIter.nextBinding() ;
Node n = b.get(var_x) ;
System.out.println(NodeFmtLib.displayStr(n)) ;
System.out.println(b) ;
}
qIter.close() ;
}
else
{
// -------- Or make ResultSet from it (but not both - reading an
// iterator consumes the current solution)
List<String> varNames = new ArrayList<String>() ;
varNames.add("x") ;
varNames.add("z") ;
ResultSet rs = new ResultSetStream(varNames, m, qIter);
ResultSetFormatter.out(rs) ;
qIter.close() ;
}
System.exit(0) ;
}
private static Model makeModel()
{
String BASE = "http://example/" ;
Model model = ModelFactory.createDefaultModel() ;
model.setNsPrefix("", BASE) ;
Resource r1 = model.createResource(BASE+"r1") ;
Resource r2 = model.createResource(BASE+"r2") ;
Property p1 = model.createProperty(BASE+"p") ;
Property p2 = model.createProperty(BASE+"p2") ;
RDFNode v1 = model.createTypedLiteral("1", XSDDatatype.XSDinteger) ;
RDFNode v2 = model.createTypedLiteral("2", XSDDatatype.XSDinteger) ;
r1.addProperty(p1, v1).addProperty(p1, v2) ;
r1.addProperty(p2, v1).addProperty(p2, v2) ;
r2.addProperty(p1, v1).addProperty(p1, v2) ;
return model ;
}
}