Hi!
I make a simple program to test TDB but I don't reach the starting line.
I attach the code:
*************
Location directory = new Location("data/DB4");
Dataset dataset = TDBFactory.createDataset(directory);
OntModel model1 =
ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM_RDFS_INF,
dataset.getNamedModel(NS));
dataset.addNamedModel("hello", model1);
dataset.close();
//the ontology is loaded at model1 perfectly
And now, I try to see if the model was saved.
Dataset dataset2 = TDBFactory.createDataset(directory);
Iterator<String> listNames = dataset2.listNames();
while (listNames.hasNext()){
String name=listNames.next();
System.out.println(name);
}
I hope to find the word-model "hello" but no...
I obtain the next exception:
Exception in thread "main" java.lang.NullPointerException
at
com.hp.hpl.jena.tdb.store.DatasetGraphTDB.listGraphNodes(DatasetGraphTDB.java:258)
at
com.hp.hpl.jena.tdb.migrate.DatasetGraphTrackActive.listGraphNodes(DatasetGraphTrackActive.java:129)
at
com.hp.hpl.jena.sparql.core.DatasetImpl.listNames(DatasetImpl.java:232)
at ip.testJena.App.main(App.java:52)
What is wrong with that simple example?
Thanks
Isaac
