I've a an n-triple file that i need to store it in a database through Jena SDB Model. I've write the following code to do that. But i struggle with a java.lang.NullPointerException that I don't really have any clue about what made it to happen and how to fix it. Here is the code :
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import com.hp.hpl.jena.db.DBConnection;
import com.hp.hpl.jena.ontology.OntModel;
import com.hp.hpl.jena.ontology.ProfileRegistry;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.ModelFactory;
import com.hp.hpl.jena.rdf.model.ModelMaker;
public class JenaRepositoryManagement {
private MySQLAccess mysql = null;
private String dbname = null;
private String xmlbase = "http://www.test.org/test.owl#";
private OntModel domainModel = null;
public JenaRepositoryManagement (String databaseName) {
dbname = "sdb_" + databaseName;
mysql = new MySQLAccess();
mysql.createDatabase(dbname);
impotring();
}
public void importing() {
// Instantiate the MySQL driver
try {
Class.forName("com.mysql.jdbc.Driver");
// Create a database connection object
DBConnection connection = new DBConnection("jdbc:mysql://localhost/"+dbname, "root", "", "MySQL");
// Get a ModelMaker for database-backed models
ModelMaker maker = ModelFactory.createModelRDBMaker(connection);
Model traceModel = maker.createModel("testModel");
// Start a database transaction. Without one, each statement will be auto-committed
traceModel.begin();
InputStream in = this.getClass().getClassLoader().getResourceAsStream("data/nts/100.nt");
traceModel.read(in, xmlbase, "N-TRIPLE");
traceModel.write(System.out);
// Commit the database transaction
traceModel.commit();
} catch (ClassNotFoundException | FileNotFoundException e) {
e.printStackTrace();
}
}
}
Here is the output during the execution
CREATE DATABASE IF NOT EXISTS sdb_100_n;
java.lang.NullPointerException
at java.io.Reader.<init>(Reader.java:78)
at java.io.InputStreamReader.<init>(InputStreamReader.java:129)
at com.hp.hpl.jena.util.FileUtils.asUTF8(FileUtils.java:51)
at com.hp.hpl.jena.rdf.model.impl.NTripleReader.read(NTripleReader.java:72)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.read(ModelCom.java:226)
at soctrace.JenaRepositoryManagement.importing(JenaRepositoryManagement.java:70)
at soctrace.views.Main$1.run(Main.java:165)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:727)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:688)
at java.awt.EventQueue$3.run(EventQueue.java:686)
at java.security.AccessController.doPrivileged(Native Method)
at java .security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:697)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
And finally Here is a sample of the n-triple file
<http://www.test.org/test.owl#trace0> <http://www.test.org/test.owl#traceContainsEvent> <http://www.test.org/test.owl#event0> .
<http://www.test.org/test.owl#event0> <http://www.test.org/test.owl#hasTime> <http://www.test.org/test.owl#interval0> .
<http://www.test.org/test.owl#event0> <http://www.test.org/test.owl#hasActiveTime> <http://www.test.org/test.owl#aduration0> .
<http://www.test.org/test.owl#interval0> <http://www.test.org/test.owl#hasStartTime> <http://www.test.org/test.owl#stime0> .
<http://www.test.org/test.owl#interval0> <http://www.test.org/test.owl#hasEndTime> <http://www.test.org/test.owl#etime0> .
<http://www.test.org/test.owl#interval0> <http://www.test.org/test.owl#hasDuration> <http://www.test.org/test.owl#duration0> .
<http://www.test.org/test.owl#stime0> <http://www.test.org/test.owl#hasValue> "525255"^^<http://www.w3.org/2001/XMLSchema#float> .
<http://www.test.org/test.owl#etime0> <http://www.test.org/test.owl#hasValue> "0"^^<http://www.w3.org/2001/XMLSchema#float> .
<http://www.test.org/test.owl#duration0> <http://www.test.org/test.owl#hasValue> "0"^^<http://www.w3.org/2001/XMLSchema#float> .
<http://www.test.org/test.owl#aduration0> <http://www.test.org/test.owl#hasValue> "0"^^<http://www.w3.org/2001/XMLSchema#float> .
<http://www.test.org/test.owl#event0> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.test.org/test.owl#ContextSwitch> .
<http://www.test.org/test.owl#event0> <http://www.test.org/test.owl#switchFrom> <http://www.test.org/test.owl#mttd0> .
<http://www.test.org/test.owl#event0> <http://www.test.org/test.owl#switchTo> <http://www.test.org/test.owl#kptrace0> .
<http://www.test.org/test.owl#trace0> <http://www.test.org/test.owl#traceContainsEvent> <http://www.test.org/test.owl#event1> .
<http://www.test.org/test.owl#event1> <http://www.test.org/test.owl#hasTime> <http://www.test.org/test.owl#interval1> .
<http://www.test.org/test.owl#event1> <http://www.test.org/test.owl#hasActiveTime> <http://www.test.org/test.owl#aduration1> .
<http://www.test.org/test.owl#interval1> <http://www.test.org/test.owl#hasStartTime> <http://www.test.org/test.owl#stime1> .
<http://www.test.org/test.owl#interval1> <http://www.test.org/test.owl#hasEndTime> <http://www.test.org/test.owl#etime1> .
<http://www.test.org/test.owl#interval1> <http://www.test.org/test.owl#hasDuration> <http://www.test.org/test.owl#duration1> .
<http://www.test.org/test.owl#stime1> <http://www.test.org/test.owl#hasValue> "525292"^^<http://www.w3.org/2001/XMLSchema#float> .
<http://www.test.org/test.owl#etime1> <http://www.test.org/test.owl#hasValue> "525306"^^<http://www.w3.org/2001/XMLSchema#float> .
<http://www.test.org/test.owl#duration1> <http://www.test.org/test.owl#hasValue> "14"^^<http://www.w3.org/2001/XMLSchema#float> .
<http://www.test.org/test.owl#aduration1> <http://www.test.org/test.owl#hasValue> "14"^^<http://www.w3.org/2001/XMLSchema#float> .
<http://www.test.org/test.owl#event1> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.test.org/test.owl#TaskRunning> .
<http://www.test.org/test.owl#event1> <http://www.test.org/test.owl#runningTask> <http://www.test.org/test.owl#kptrace0> .
thanks in advance.
Based on this code (I'm guessing on the line numbers, but I'm pretty sure I'm right):
/* 69 */ InputStream in = this.getClass().getClassLoader().getResourceAsStream("data/nts/100.nt");
/* 70 */ traceModel.read(in, xmlbase, "N-TRIPLE");
and the beginning of the stacktrace:
java.lang.NullPointerException
at java.io.Reader.<init>(Reader.java:78)
at java.io.InputStreamReader.<init>(InputStreamReader.java:129)
at com.hp.hpl.jena.util.FileUtils.asUTF8(FileUtils.java:51)
at com.hp.hpl.jena.rdf.model.impl.NTripleReader.read(NTripleReader.java:72)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.read(ModelCom.java:226)
…
I'd guess that in is null. Maybe that pathname needs to be "/data/nts/100.nt" (note the / at the beginning).
The stacktrace contains line numbers, and I'm pretty sure they point you to the problematic line. This is something that shouldn't be too hard to run in a debugger. Even if you can't run it in a debugger, if you're getting a null pointer exception, and you have a reference to a particular line, it's typically a good idea to check which values are used on that line and check whether they're null or not. In this case, you could just do:
InputStream in = this.getClass().getClassLoader().getResourceAsStream("data/nts/100.nt");
Objects.requireNonNull( in, "InputStream for resource data/nts/100.nt should not be null." );
traceModel.read(in, xmlbase, "N-TRIPLE");