Exception when creating/closing/creating a dataset (jena 2.7.4, was OK with TDB-0.8.10)

[François-Paul Servant]

Dear Jena users,

here is a test case that worked with TDB-0.8.10 but throws an exception with 
jena 2.7.4. In short, you cannot anymore create a TDB dataset from a dir, close 
it, and then create it again.

package ex;
import java.io.File;
import org.junit.Before;
import org.junit.Test;
import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.StmtIterator;
import com.hp.hpl.jena.tdb.TDBFactory;

public class TDBProblem {
        File tdbDir;
        Dataset ds;

        @Before
        public void setUp() throws Exception {
                tdbDir = new File("/Users/fps/Desktop/TDBTest");
        }

        @Test
        public final void test1() {
                openAndClose();
        }

        @Test
        public final void test2() {
                open();
        }

        @Test
        public final void test3() {
                openAndClose();
                open();
        }

        void openAndClose() {
                Dataset ds = TDBFactory.createDataset(tdbDir.getAbsolutePath());
                Model m = ds.getDefaultModel();
                m.add(m.createResource("http://foo.com/s";),
                                m.createProperty("http://foo.com/p";),
                                m.createResource("http://foo.com/o";));
                m.commit();
                ds.close();
        }

        void open() {
                Dataset ds = TDBFactory.createDataset(tdbDir.getAbsolutePath());
                // EXCEPTION HERE WITH JENA 2.7.4:
                Model m = ds.getDefaultModel();
                StmtIterator it = m.listStatements();
                for(;it.hasNext();) {
                        System.out.println(it.next());
                }
        }
}

The exception you get (on ds.getDefaultModel()) is: 
java.lang.NullPointerException
        at 
com.hp.hpl.jena.tdb.store.GraphTriplesTDB.createPrefixMapping(GraphTriplesTDB.java:92)
        at 
com.hp.hpl.jena.sparql.graph.GraphBase2.getPrefixMapping(GraphBase2.java:194)
        at 
com.hp.hpl.jena.rdf.model.impl.ModelCom.getPrefixMapping(ModelCom.java:908)
        at 
com.hp.hpl.jena.rdf.model.impl.ModelCom.withDefaultMappings(ModelCom.java:952)
        at com.hp.hpl.jena.rdf.model.impl.ModelCom.<init>(ModelCom.java:66)
        at com.hp.hpl.jena.rdf.model.impl.ModelCom.<init>(ModelCom.java:62)
        at 
com.hp.hpl.jena.rdf.model.ModelFactory.createModelForGraph(ModelFactory.java:166)
        at 
com.hp.hpl.jena.sparql.core.DatasetImpl.graph2model(DatasetImpl.java:266)
        at 
com.hp.hpl.jena.sparql.core.DatasetImpl.getDefaultModel(DatasetImpl.java:102)
        at ex.TDBProblem.open(TDBProblem.java:48)

Best,

fps