jena-arq/src/test/java/org/apache/jena/riot/TestJsonLDReader.java

/*
 * 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 org.apache.jena.riot;

import static org.junit.Assert.assertTrue;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.github.jsonldjava.utils.JsonUtils;

import org.apache.jena.query.Dataset;
import org.apache.jena.query.DatasetFactory;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.ModelFactory;
import org.apache.jena.riot.system.ErrorHandlerFactory;
import org.apache.jena.sparql.util.Context;
import org.apache.jena.vocabulary.RDF;
import org.junit.Test;

public class TestJsonLDReader {

    @Test
    public final void simpleReadTest() {
        try {
            String jsonld = someSchemaDorOrgJsonld();
            Model m = ModelFactory.createDefaultModel();
            RDFParser.create()
                .errorHandler(ErrorHandlerFactory.errorHandlerNoLogging)
                .fromString(jsonld)
                .lang(Lang.JSONLD)
                .parse(m);
            assertJohnDoeIsOK(m);
        } catch (RiotException e) {
            // cf. org.apache.jena.riot.RiotException: loading remote context failed: http://schema.org/
            // There's a line printed anyway
            // e.printStackTrace();
        }
    }

    /** Test using the jena Context mechanism to pass the jsonld "@context" */
    @Test public final void overrideAtContextTest() throws JsonGenerationException, IOException {
        // some jsonld using schema.org's URI as "@context"
        String jsonld = someSchemaDorOrgJsonld();

        // a subset of schema.org that can be used as @context for jsonld
        String jsonldContext = "{\"name\":{\"@id\":\"http://schema.org/name\"},\"Person\": {\"@id\": \"http://schema.org/Person\"}}";

        // pass the jsonldContext to the read using a jena Context
        Context jenaCtx = new Context();
        Object jsonldContextAsMap = JsonUtils.fromInputStream(new ByteArrayInputStream(jsonldContext.getBytes(StandardCharsets.UTF_8)));
        jenaCtx.set(RIOT.JSONLD_CONTEXT, jsonldContextAsMap);

        // read the jsonld, replacing its "@context"
        Dataset ds = jsonld2dataset(jsonld, jenaCtx);

        // check ds is correct
        assertJohnDoeIsOK(ds.getDefaultModel());
    }

    /** Not really useful, but one can replace the @context by a URI: in this case, this URI is used when expanding the json
     * (letting JSON-LD java API taking care of downloading the context. */
    // well, as of this writing, it doesn't work, as we get a "loading remote context failed"
    // But it is about the replacing URI, not the replaced one, showing that the mechanism does work
    @Test public final void overrideAtContextByURITest() throws JsonGenerationException, IOException {
        // some jsonld using a (fake) pseudo.schema.org's URI as "@context"
        String jsonld = "{\"@id\":\"_:b0\",\"@type\":\"Person\",\"name\":\"John Doe\",\"@context\":\"http://pseudo.schema.org/\"}";

        // a subset of schema.org that can be used as @context for jsonld
        String jsonldContext = "\"http://schema.org\"";

        // pass the jsonldContext to the read using a jena Context
        Context jenaCtx = new Context();
        Object jsonldContextAsObject = JsonUtils.fromInputStream(new ByteArrayInputStream(jsonldContext.getBytes(StandardCharsets.UTF_8)));
        jenaCtx.set(RIOT.JSONLD_CONTEXT, jsonldContextAsObject);

        try {
            // read the jsonld, replacing its "@context"
            Dataset ds = jsonld2dataset(jsonld, jenaCtx);

            // check ds is correct
            assertJohnDoeIsOK(ds.getDefaultModel());
        } catch (RiotException e) {
            // cf. org.apache.jena.riot.RiotException: loading remote context failed: http://schema.org/
            // There's a line printed anyway
            // e.printStackTrace();
        }
    }

    //
    //
    //

    /**
     * Reading some jsonld String, using a Context
     * @return a new Dataset
     * @throws IOException
     */
    private Dataset jsonld2dataset(String jsonld, Context jenaCtx) throws IOException {
        Dataset ds = DatasetFactory.create();

        try (InputStream in = new ByteArrayInputStream(jsonld.getBytes(StandardCharsets.UTF_8))) {
            RDFParser.create()
                .source(in)
                .errorHandler(ErrorHandlerFactory.errorHandlerNoLogging)
                .lang(Lang.JSONLD)
                .context(jenaCtx)
                .parse(ds.asDatasetGraph());
        }

        return ds;
    }

    /** Example data */
    private String someSchemaDorOrgJsonld() {
        return "{\"@id\":\"_:b0\",\"@type\":\"Person\",\"name\":\"John Doe\",\"@context\":\"http://schema.org/\"}";
    }

    /** Checking that the data loaded from someSchemaDorOrgJsonld into a model, is OK */
    private void assertJohnDoeIsOK(Model m) {
        assertTrue(m.contains(null, RDF.type, m.createResource("http://schema.org/Person")));
        assertTrue(m.contains(null, m.createProperty("http://schema.org/name"), "John Doe"));       
    }


}