Export SPARQL query results into json file in sesame

Question

I need to export SPARQL query results into JSON using Sesame. Should I use the class SPARQLResultsJSONWriter? How would this be implemented (in Java)?

Answer 1

This is actually explained in the Sesame Repository API user documentation, with code examples to demonstrate.

However, to reiterate: once you have prepared a query by using RepositoryConnection.prepareTupleQuery, you can evaluate the returned TupleQuery object in two ways: one is by calling evaluate(), in which case the evaluation method will return a TupleQueryResult object. The other is by calling evaluate(TupleQueryResultHandler) and passing it a TupleQueryResultHandler instance, of which SPARQLResultJSONWriter is a subclass. So all you need to is bring the pieces together, like so:

RepositoryConnection conn = rep.getConnection();
try {
   // prepare the query
   String queryString = "SELECT * WHERE {?s ?p ?o . }";
   TupleQuery query = conn.prepareTupleQuery(QueryLanguage.SPARQL, queryString);

   // open a file to write the result to it in JSON format
   OutputStream out = new FileOutputStream("/path/to/output.json");
   TupleQueryResultHandler writer = new SPARQLResultJSONWriter(out);

   // execute the query and write the result directly to file
   query.evaluate(writer);  
}
finally {
   conn.close();
}