Java tutorial
/* * Licensed 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 org.trellisldp.triplestore; import static java.util.Objects.nonNull; import static java.util.Optional.empty; import static java.util.Optional.of; import static org.apache.jena.query.DatasetFactory.wrap; import java.util.Optional; import org.apache.commons.rdf.api.BlankNodeOrIRI; import org.apache.commons.rdf.api.Dataset; import org.apache.commons.rdf.api.IRI; import org.apache.commons.rdf.api.RDFTerm; import org.apache.commons.rdf.api.Triple; import org.apache.commons.rdf.jena.JenaDataset; import org.apache.commons.rdf.jena.JenaRDF; import org.apache.jena.query.QuerySolution; import org.apache.jena.rdf.model.RDFNode; import org.apache.jena.sparql.core.DatasetGraph; import org.apache.jena.sparql.core.DatasetGraphFactory; import org.apache.jena.sparql.core.Var; /** * Utilities for the Triplestore resource service. */ final class TriplestoreUtils { private static final JenaRDF rdf = new JenaRDF(); public static final Var SUBJECT = Var.alloc("subject"); public static final Var PREDICATE = Var.alloc("predicate"); public static final Var OBJECT = Var.alloc("object"); public static JenaRDF getInstance() { return rdf; } public static BlankNodeOrIRI getSubject(final QuerySolution qs) { return (BlankNodeOrIRI) rdf.asRDFTerm(qs.get("subject").asNode()); } public static IRI getPredicate(final QuerySolution qs) { return (IRI) rdf.asRDFTerm(qs.get("predicate").asNode()); } public static RDFTerm getObject(final QuerySolution qs) { return rdf.asRDFTerm(qs.get("object").asNode()); } public static RDFTerm getBaseIRI(final RDFTerm object) { if (object instanceof IRI) { final String iri = ((IRI) object).getIRIString().split("#")[0]; return rdf.createIRI(iri); } return object; } public static Optional<Triple> nodesToTriple(final RDFNode s, final RDFNode p, final RDFNode o) { if (nonNull(s) && nonNull(p) && nonNull(o)) { return of(rdf.createTriple((BlankNodeOrIRI) rdf.asRDFTerm(s.asNode()), (IRI) rdf.asRDFTerm(p.asNode()), rdf.asRDFTerm(o.asNode()))); } return empty(); } /** * TODO Replace when COMMONSRDF-74 is released. * * @param dataset a Commons RDF {@link Dataset} * @return a Jena {@link org.apache.jena.query.Dataset} */ public static org.apache.jena.query.Dataset asJenaDataset(final Dataset dataset) { final DatasetGraph dsg; if (dataset instanceof JenaDataset) { dsg = ((JenaDataset) dataset).asJenaDatasetGraph(); } else { dsg = DatasetGraphFactory.createGeneral(); dataset.stream().map(rdf::asJenaQuad).forEach(dsg::add); } return wrap(dsg); } private TriplestoreUtils() { // prevent instantiation } }