Hi,

I have a strange behaviour on JenaTDB when i'm executing a SPARQL query
more one time.

The first execution is ok, but from the second one i have this exception

Exception in thread "main" java.lang.NullPointerException
  at
com.hp.hpl.jena.tdb.store.DatasetPrefixesTDB.readPrefixMap(DatasetPrefixesTDB.java:174)
  at
com.hp.hpl.jena.sparql.graph.GraphPrefixesProjection.getNsPrefixMap(GraphPrefixesProjection.java:62)
  at
com.hp.hpl.jena.tdb.store.DatasetPrefixesTDB.getPrefixMapping(DatasetPrefixesTDB.java:223)
  at
com.hp.hpl.jena.tdb.store.DatasetPrefixesTDB.getPrefixMapping(DatasetPrefixesTDB.java:214)
  at
com.hp.hpl.jena.tdb.store.GraphTDB.createPrefixMapping(GraphTDB.java:78)
  at
com.hp.hpl.jena.graph.impl.GraphBase.getPrefixMapping(GraphBase.java:186)
  at
com.hp.hpl.jena.rdf.model.impl.ModelCom.getPrefixMapping(ModelCom.java:980)
  at
com.hp.hpl.jena.rdf.model.impl.ModelCom.withDefaultMappings(ModelCom.java:1024)
  at com.hp.hpl.jena.rdf.model.impl.ModelCom.<init>(ModelCom.java:74)
  at com.hp.hpl.jena.rdf.model.impl.ModelCom.<init>(ModelCom.java:70)
  at
com.hp.hpl.jena.rdf.model.ModelFactory.createModelForGraph(ModelFactory.java:176)
  at
com.hp.hpl.jena.sparql.core.DatasetImpl.graph2model(DatasetImpl.java:271)
  at
com.hp.hpl.jena.sparql.core.DatasetImpl.getDefaultModel(DatasetImpl.java:103)
  at
fr.ensma.lias.qarscore.connection.implementation.JenaSession.set_model(JenaSession.java:187)
  at
fr.ensma.lias.qarscore.connection.implementation.SessionJenaTDB.<init>(SessionJenaTDB.java:56)
  at
fr.ensma.lias.qarscore.connection.implementation.SessionJenaTDB.getSessionTDB(SessionJenaTDB.java:45)
  at
fr.ensma.lias.qarscore.connection.SessionFactory.getTDBSession(SessionFactory.java:73)
  at fr.ensma.lias.qarscore.Test.<init>(Test.java:33)
  at fr.ensma.lias.qarscore.Test.main(Test.java:59)

The JenaTDB repository after the first execution was changed. Two file have
been impacted: prefix2id.dat prefixIdx.dat

Curiously, this problem was occurred on both Linux and MAC operating system
not on Windows OS platform.

Do you have an idea about this problem ?

Thanks

Mickael

-- 
Research Engineer in Computer Science at LIAS/ISAE-ENSMA
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