Re: [jira] [Created] (JENA-1292) almost impossible to get @vocab prefix in JsonLDContext

[François-Paul Servant]

Hi Elie,

(I wrote the comment in the line you point to. And then forgot it).

The fix is probably more than one line (it must take care of the other parts of 
the definition of the “context" passed to the JSON-LD java API, and of the 
behavior of that API when it includes an @vocab)

I’ll try to see what can be done. In the meantime, you maybe can use a new 
possibility in 3.2.0: you can access the object that jena creates and pass to 
the JSON-LD java API. You can modify it before sending it to the JSON-LD java 
API. Please find below a quick example.

HTH

fps

/* Created on 20 févr. 2017 */
package com.renault.sicg.rasse.commons;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.jena.query.DatasetFactory;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.ModelFactory;
import org.apache.jena.rdf.model.Resource;
import org.apache.jena.riot.RDFFormat;
import org.apache.jena.riot.system.PrefixMap;
import org.apache.jena.riot.system.RiotLib;
import org.apache.jena.riot.writer.JsonLDWriter;
import org.apache.jena.sparql.core.DatasetGraph;
import org.apache.jena.sparql.util.Context;
import org.apache.jena.sparql.vocabulary.FOAF;
import org.apache.jena.vocabulary.RDF;
import org.junit.Test;

import com.fasterxml.jackson.core.JsonParseException;
import com.github.jsonldjava.core.JsonLdError;
import com.github.jsonldjava.utils.JsonUtils;

public class AtVocab {
@Test public final void test() throws JsonParseException, JsonLdError, 
IOException {
  Model m = ModelFactory.createDefaultModel();
  String ns = "http://schema.org/";;
  Resource person = m.createResource(ns + "Person");
  Resource s = m.createResource();
  m.add(s, m.createProperty(ns + "name"), "Jane Doe");
  m.add(s, m.createProperty(ns + "url"), "http://www.janedoe.com";);
  m.add(s, m.createProperty(ns + "jobTitle"), "Professor");
  m.add(s, FOAF.nick, "jd");
  m.add(s, RDF.type, person);
  
  m.setNsPrefix("", ns);
  
  DatasetGraph g = DatasetFactory.create(m).asDatasetGraph();
  PrefixMap pm = RiotLib.prefixMap(g);
  String base = null;
  Context jenaContext = null;
  
  // the JSON-LD API object. It's a map
  Map map = (Map) 
JsonLDWriter.toJsonLDJavaAPI((RDFFormat.JSONLDVariant)RDFFormat.JSONLD.getVariant()
          , g, pm, base, jenaContext);

  // get the @context:
  Map<String, Object> ctx = (Map<String, Object>) map.get("@context");
  
  // add the "@vocab" key, to ctx
  // and remove from it declaration of props in ns
  
  // remove from ctx declaration of props in ns
  List<String> remove = new ArrayList<>();
  for (Entry<String, Object> e : ctx.entrySet()) {
      // is it the declaration of a prop in ns?
      Object o = e.getValue();
      if (o instanceof Map) {
          o = ((Map) o).get("@id");
      }           
      if ((o != null) && (o instanceof String)) {
          if (((String) o).equals(ns + e.getKey())) {
              remove.add(e.getKey());
          }
      }
  }
  for (String key : remove) {
      ctx.remove(key);
  }
  
  // add the "@vocab" key to ctx 
  ctx.put("@vocab", "http://schema.org/";);
  
  JsonUtils.writePrettyPrint(new PrintWriter(System.out), map) ;
}

}