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" .