Initialising Apache Jena TDB Dataset - jena

Question

I am using Apache Jena from within Tomcat 8 under Windows 10 (Eclipse IDE) and am not able to initialise the TDB Dataset. The initialisation code is put in the static initialiser inside a try-catch block but no exception is being thrown and the finally clause is getting invoked. I tried with relative directory names, absolute path names, as well as empty path (in memory dataset). The
dataset remains null and so triples cannot be written. What do I need to change in the code
to initialise the dataset?
Here is the code:
package knowledgegraph;
import org.apache.jena.tdb.TDBFactory;
import org.apache.jena.rdf.model.*;
import org.apache.jena.shared.JenaException;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import org.apache.jena.query.Dataset;
import org.apache.jena.query.ReadWrite;
public class JenaProcessor {
static Dataset dataset = null;
static String ns = "http://www.lke.com/lke.owl#";
static {
try {
// dataset = TDBFactory.createDataset("lke");
// dataset = TDBFactory.createDataset("C:\\Users\\Diptendu\\Desktop\\lke");
dataset = TDBFactory.createDataset();
System.out.println("TDB initialised");
}
// catch(Exception ex) {
catch(JenaException ex) {
ex.printStackTrace();
}
finally {
System.out.println("Finally clause");
}
}
static public void writeTriple(String corpus_file_id, String subject, String predicate, String object) {
dataset.begin(ReadWrite.WRITE) ;
Model model = null;
try {
model = dataset.getNamedModel(corpus_file_id);
// model.enterCriticalSection(Lock.WRITE);
// write triples to model
Resource subjectResource = model.createResource(ns.concat(subject));
Property property = model.createProperty(ns.concat(predicate));
Resource objectResource = model.createResource(ns.concat(object));
// model.add(subjectResource, property, objectResource);
Statement statement = model.createStatement(subjectResource, property, objectResource);
model.add(statement);
dataset.commit();
// TDB.sync(model);
} finally {
// model.leaveCriticalSection();
model.close();
dataset.end();
}
}
}

Answer 1

sked and responded to on users#jena:
https://lists.apache.org/thread.html/r9f788bf21ceb3991329ab0ba3c649d94f2983f92aa3c0a76af788e52%40%3Cusers.jena.apache.org%3E
It's because you are trying to close the model after you've committed
the transaction so the error message is quite correct in that you are
no longer in a transaction at that point
Put the dataset.commit() after the model.close() line and it will work
Rob