A code example of serialization JSON to JSON-LD in Java?

I need to convert a some mass of data represented in the form of JSON to JSON-LD. I want to do this with this JSON-LD Java implementation, but I don’t understand, what should I do.

I watched several tutorials and read something about JSON-LD on the Internet, but do not understand the simplest thing: how do I convert JSON to JSON-LD?

For example, I have this code in JSON:

{
   "name" : "Andreas",
   "age" : 20,
   "profession" : "student",
   "personalWebsite" : "example.com"
}

What should I do now? Something like context.add("example.com")?

InputStream inputStream = new FileInputStream("C:UsersUsernameinput.json");
Object jsonObject = JsonUtils.fromInputStream(inputStream);
Map context = new HashMap();
JsonLdOptions options = new JsonLdOptions();

Answer

Add a ‘@context’ entry to your data.

{
   "name" : "Andreas",
   "age" : 20,
   "profession" : "student",
   "personalWebsite" : "example.com",
   "@context":"http://schema.org/"
}

Your JSON-LD Processor will do the rest (since version 0.9)

As test you can convert your json to rdf.

package overflow.stack2449461;

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.StringWriter;
import java.util.Collection;


import org.eclipse.rdf4j.model.Statement;
import org.eclipse.rdf4j.rio.RDFFormat;
import org.eclipse.rdf4j.rio.RDFHandlerException;
import org.eclipse.rdf4j.rio.RDFParser;
import org.eclipse.rdf4j.rio.RDFWriter;
import org.eclipse.rdf4j.rio.Rio;
import org.eclipse.rdf4j.rio.helpers.StatementCollector;


public class Test {
    @org.junit.Test
    public void testForYourCode() {
        String data = "{"name" : "Andreas","age" : 20,"profession" : "student", "personalWebsite" : "example.com","@context": "http://schema.org/"}";
        try (InputStream in = new ByteArrayInputStream(data.getBytes("utf-8"))) {
            String dataAsRdf = readRdfToString(in, RDFFormat.JSONLD, RDFFormat.NTRIPLES, "");
            System.out.println(dataAsRdf);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * @param in
     *            a rdf input stream
     * @param inf
     *            the rdf format of the input stream
     * @param outf
     *            the output format
     * @param baseUrl
     *            usually the url of the resource
     * @return a string representation
     */
    public static String readRdfToString(InputStream in, RDFFormat inf, RDFFormat outf, String baseUrl) {
        Collection<Statement> myGraph = null;
        myGraph = readRdfToGraph(in, inf, baseUrl);
        return graphToString(myGraph, outf);
    }

    /**
     * @param inputStream
     *            an Input stream containing rdf data
     * @param inf
     *            the rdf format
     * @param baseUrl
     *            see sesame docu
     * @return a Graph representing the rdf in the input stream
     */
    public static Collection<Statement> readRdfToGraph(final InputStream inputStream, final RDFFormat inf,
            final String baseUrl) {
        try {
            final RDFParser rdfParser = Rio.createParser(inf);
            final StatementCollector collector = new StatementCollector();
            rdfParser.setRDFHandler(collector);
            rdfParser.parse(inputStream, baseUrl);
            return collector.getStatements();
        } catch (final Exception e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Transforms a graph to a string.
     * 
     * @param myGraph
     *            a sesame rdf graph
     * @param outf
     *            the expected output format
     * @return a rdf string
     */
    public static String graphToString(Collection<Statement> myGraph, RDFFormat outf) {
        StringWriter out = new StringWriter();
        RDFWriter writer = Rio.createWriter(outf, out);
        try {
            writer.startRDF();
            for (Statement st : myGraph) {
                writer.handleStatement(st);
            }
            writer.endRDF();
        } catch (RDFHandlerException e) {
            throw new RuntimeException(e);
        }
        return out.getBuffer().toString();
    }

}

With pom.xml

   <dependency>
        <groupId>org.eclipse.rdf4j</groupId>
        <artifactId>rdf4j-runtime</artifactId>
        <version>2.2</version>
        <type>pom</type>
    </dependency>
    <dependency>
        <groupId>com.github.jsonld-java</groupId>
        <artifactId>jsonld-java</artifactId>
        <version>0.10.0</version>
    </dependency>

It will print your json string as rdf NTRIPLES

_:b0 <http://schema.org/age> "20"^^<http://www.w3.org/2001/XMLSchema#integer> .
_:b0 <http://schema.org/name> "Andreas" .
_:b0 <http://schema.org/personalWebsite> "example.com" .
_:b0 <http://schema.org/profession> "student" .

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