| /* |
| * 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; |
| |
| |
| // The ARQ application API. |
| import org.apache.jena.atlas.io.IndentedWriter ; |
| import org.apache.jena.graph.Triple ; |
| import org.apache.jena.query.* ; |
| import org.apache.jena.rdf.model.* ; |
| import org.apache.jena.sparql.core.Var ; |
| import org.apache.jena.sparql.syntax.ElementGroup ; |
| import org.apache.jena.vocabulary.DC ; |
| |
| /** Example : Build a query syntax programmatically. |
| * |
| * Note: it is often better to build and execute an algebra expression. See other examples. */ |
| |
| public class ExProg1 |
| { |
| static public final String NL = System.getProperty("line.separator") ; |
| |
| public static void main(String[] args) |
| { |
| Model model = createModel() ; |
| |
| Query query = QueryFactory.make() ; |
| |
| query.setQuerySelectType() ; |
| |
| // Build pattern |
| |
| ElementGroup elg = new ElementGroup() ; |
| |
| Var varTitle = Var.alloc("title") ; |
| Var varX = Var.alloc("x") ; |
| |
| Triple t1 = new Triple(varX, DC.title.asNode(), varTitle) ; |
| elg.addTriplePattern(t1) ; |
| |
| // Don't use bNodes for anon variables. The conversion is done in parsing. |
| // BNodes here are assumed to be values from the target graph. |
| Triple t2 = new Triple(varX, DC.description.asNode(), Var.alloc("desc")) ; |
| elg.addTriplePattern(t2) ; |
| |
| // Attach the group to query. |
| query.setQueryPattern(elg) ; |
| |
| // Choose what we want - SELECT * |
| //query.setQueryResultStar(true) ; |
| query.addResultVar(varTitle) ; |
| |
| // Print query with line numbers |
| // Prefix mapping just helps serialization |
| query.getPrefixMapping().setNsPrefix("dc" , DC.getURI()) ; |
| query.serialize(new IndentedWriter(System.out,true)) ; |
| System.out.println() ; |
| |
| try ( QueryExecution qexec = QueryExecutionFactory.create(query, model) ) { |
| // Assumption: it's a SELECT query. |
| ResultSet rs = qexec.execSelect() ; |
| |
| // The order of results is undefined. |
| System.out.println("Titles: ") ; |
| for ( ; rs.hasNext() ; ) |
| { |
| QuerySolution rb = rs.nextSolution() ; |
| |
| // Get title - variable names do not include the '?' (or '$') |
| RDFNode x = rb.get("title") ; |
| |
| // Check the type of the result value |
| if ( x instanceof Literal ) |
| { |
| Literal titleStr = (Literal)x ; |
| System.out.println(" "+titleStr) ; |
| } |
| else |
| System.out.println("Strange - not a literal: "+x) ; |
| |
| } |
| } |
| } |
| |
| public static Model createModel() |
| { |
| Model model = ModelFactory.createDefaultModel() ; |
| |
| Resource r1 = model.createResource("http://example.org/book#1") ; |
| Resource r2 = model.createResource("http://example.org/book#2") ; |
| Resource r3 = model.createResource("http://example.org/book#3") ; |
| |
| r1.addProperty(DC.title, "SPARQL - the book") |
| .addProperty(DC.description, "A book about SPARQL") ; |
| |
| r2.addProperty(DC.title, "Advanced techniques for SPARQL") ; |
| |
| r3.addProperty(DC.title, "Jena - an RDF framework for Java") |
| .addProperty(DC.description, "A book about Jena") ; |
| |
| return model ; |
| } |
| } |