[JAVA] A memorandum when you want to see the data acquired by Jena & SPARQL for each variable.

When I googled with Jena & SPARQL ...

I usually write like this.

JenaSample.java

String queryString = "(SPARQL)";
Query query = QueryFactory.create(queryString);
QueryExecution qe = QueryExecutionFactory.sparqlService(service, query);
ResultSet results = qe.execSelect();
ResultSetFormatter.out(System.out,results, query);

The results are displayed in a list, and I'm happy. I'd like to say ... What should I do if I want to get the value for each variable?

Resource and Literal classes

For example, when requesting a food ingredient LOD SPARQL endpoint. Food Ingredients LOD

SPARQL looks like this.

SPARQL

PREFIX schema: <http://schema.org/>
PREFIX rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX cc:     <http://creativecommons.org/ns#>
PREFIX dc:     <http://purl.org/dc/elements/1.1/>
PREFIX xsd:    <http://www.w3.org/2001/XMLSchema#>
SELECT DISTINCT ?name ?calories ?sodiumContent ?nutritionType ?title
WHERE {
	?s schema:category "seafood";
	   schema:name ?name;
	   schema:nutrition ?nutrition;
	   cc:attributionName ?attributionName.
	?nutrition schema:calories ?calories;
	           schema:sodiumContent ?sodiumContent;
	           rdf:type  ?nutritionType.
	?attributionName dc:title ?title.
}
LIMIT 10

In Java, try taking it out like this.

JenaSample2.java

Query query = QueryFactory.create(queryString);
QueryExecution qe = QueryExecutionFactory.sparqlService(service, query);
ResultSet results = qe.execSelect();
while (results.hasNext()) {
	QuerySolution qs = results.next();

	RDFNode node = qs.get("s");
	Resource resource = node.asResource();
	System.out.println(resource.getURI());

	RDFNode node2 = qs.get("calories");
	Literal literal = node2.asLiteral();
	System.out.println(literal.getInt());
}

Explaining the source ...

1. It is possible to loop with hasNext () like ResultSet in SQL.
2. Get one result as a QuerySolution object
3. Get the value of each variable with an RDFNode object
4. Get data with asResource () for resources and asLiteral () for literals
5. The value can be obtained with the getter of the Resource or Literal object.

As far as I can tell, it seems like this. If you use it incorrectly, please point it out. m (_ "_ m)