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Home » Semantic technologies » RDF Stores » Jena TDB2 » Creating, Writing and Reading Jena TDB2 Datasets

Creating, Writing and Reading Jena TDB2 Datasets

Jena TDB2 can be used as an RDF datastore. Note that TDB (version 1 of Jena TDB) and TDB2 are not compatible with each other. TDB2 is per definition transactional (while TDB is not). In this post I give a simple example that

  1. create a new Jena TDB2 dataset,
  2. create a write transaction and write data to the datastore,
  3. create a read transaction and read the data from the datastore, and
  4. release resources associated with the dataset on writing and reading is done.

Create TDB2 Dataset

To create a Jena TDB2 dataset, we use the TDB2Factory. Note that the class name is TDB2Factory and not TDBFactory. We need to specify a directory where our dataset will be created. Multiple datasets cannot be written to the same directory.

Path path = Paths.get(".").toAbsolutePath().normalize();      
String dbDir = path.toFile().getAbsolutePath() + "/db/"; 
Location location = Location.create(dbDir);      
Dataset dataset = TDB2Factory.connectDataset(location); 

Create WRITE Transaction and Write

dataset.begin(ReadWrite.WRITE);
UpdateRequest updateRequest = UpdateFactory.create(
  "INSERT DATA { " 
  + " \"Grace Hopper\" .}");
UpdateProcessor updateProcessor = 
  UpdateExecutionFactory.create(updateRequest, dataset);
updateProcessor.execute();
dataset.commit(); 

Create READ Transaction and Read

dataset.begin(ReadWrite.READ);
QueryExecution qe = QueryExecutionFactory
  .create("SELECT ?s ?p ?o WHERE {?s ?p ?o .}", dataset);
for (ResultSet results = qe.execSelect(); results.hasNext();) {
  QuerySolution qs = results.next();
  String strValue = qs.get("?o").toString();
  logger.trace("value = " + strValue);
}  

Release Dataset Resources and Run Application

The dataset resources can be release calling close() on the dataset.

dataset.close();

Running the application will cause a /db directory to be created in the directory from where you run your application, which consists of the various files that represent your dataset.

Conclusion

In this post I have given a simple example creating a TDB2 dataset and writing to and reading from it. This code can be found on github.


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