| /* |
| * 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 ; |
| } |
| |
| } |