org.trellisldp.triplestore.TriplestoreUtils Maven / Gradle / Ivy

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The core components for a Trellis linked data server

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/*
 * Copyright (c) 2021 Aaron Coburn and individual contributors
 *
 * 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.Optional.empty;
import static java.util.Optional.of;
import static org.apache.jena.commonsrdf.JenaCommonsRDF.fromJena;
import static org.apache.jena.graph.Triple.create;

import java.util.Optional;

import org.apache.commons.rdf.api.BlankNodeOrIRI;
import org.apache.commons.rdf.api.IRI;
import org.apache.commons.rdf.api.RDFTerm;
import org.apache.commons.rdf.api.Triple;
import org.apache.jena.query.QuerySolution;
import org.apache.jena.rdf.model.RDFNode;
import org.apache.jena.sparql.core.Var;

/**
 * Utilities for the Triplestore resource service.
 */
final class TriplestoreUtils {

    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 final Var TYPE = Var.alloc("type");

    public static BlankNodeOrIRI getSubject(final QuerySolution qs) {
        return (BlankNodeOrIRI) fromJena(qs.get("subject").asNode());
    }

    public static IRI getPredicate(final QuerySolution qs) {
        return (IRI) fromJena(qs.get("predicate").asNode());
    }

    public static RDFTerm getObject(final QuerySolution qs) {
        return fromJena(qs.get("object").asNode());
    }

    public static IRI getType(final QuerySolution qs) {
        return (IRI) fromJena(qs.get("type").asNode());
    }

    public static Optional nodesToTriple(final RDFNode s, final RDFNode p, final RDFNode o) {
        if (s != null && p != null && o != null) {
            return of(fromJena(create(s.asNode(), p.asNode(), o.asNode())));
        }
        return empty();
    }

    private TriplestoreUtils() {
        // prevent instantiation
    }
}