In Jena, is there a way query subject via object?

Question

I have a turtle file like this:

<http://rdf.freebase.com/ns/m.05h40wd>  <http://rdf.freebase.com/key/wikipedia.en_id>   "21537998"  .
<http://rdf.freebase.com/ns/m.05h40xf>  <http://rdf.freebase.com/key/wikipedia.en_id>   "21557390"  .
<http://rdf.freebase.com/ns/m.05h4251>  <http://rdf.freebase.com/key/wikipedia.en_id>   "21550418"  .
<http://rdf.freebase.com/ns/m.05h4__1>  <http://rdf.freebase.com/key/wikipedia.en_id>   "21495513"  .

I now only have the object(the id) but I want to get the subject. Is there a way? This is my code.

  public static void main(String[] args) throws FileNotFoundException {
      Model model=ModelFactory.createDefaultModel();
        model.read(new FileInputStream("RDFTest.ttl"),null,"TTL");
        Resource topic = model.getResource("http://rdf.freebase.com/ns/" + "m.05h4251");
          Property labelProperty = model.getProperty("http://rdf.freebase.com/key/wikipedia.en_id");
          System.out.println(topic.getProperty(labelProperty));
  }

Ands the result is :

[http://rdf.freebase.com/ns/m.05h4251, http://rdf.freebase.com/key/wikipedia.en_id, "21550418"]

If I do the reverse I will get null.

Answer 1

You can use Model#listResourcesWithProperty(Property p, RDFNode o). If you don't care what the property is, just pass null as the property to act as a wildcard. This gives you a ResIterator over the subjects, because there could be more than one (just like there could be more than one object for a property for a given subject; the method you're using getProperty, just returns an arbitrary one).