D-Net

import org.apache.jena.query.ResultSet;

import org.apache.jena.rdf.model.Resource;

	@Ignore

		String sparqlUrl = "http://localhost:8890/sparql";

		final QueryEngineHTTP serviceRequest = QueryExecutionFactory.createServiceRequest(sparqlUrl, query);

	@Ignore

	public void testDescribeRemote(){

		String resURI = "http://hdl.handle.net/11858/00-203C-0000-0029-F5E8-C";

		//now query for the resource URI

		String describeQuery = "DESCRIBE <"+resURI+">";

		Query query = QueryFactory.create(describeQuery) ;

		String sparqlUrl = "https://virtuoso.parthenos.d4science.org/sparql";

		final QueryEngineHTTP serviceRequest = QueryExecutionFactory.createServiceRequest(sparqlUrl, query);

		Model resultModel = serviceRequest.execDescribe();

		serviceRequest.close();

		resultModel.write(System.out);

	}

	@Test

	public void testReadForDescribeResource() {

		String sparqlUrl = "http://localhost:8890/sparql";

		String queryForGraphs =

				"SELECT DISTINCT ?g \n"

						+ "WHERE {\n"

						+ "  { ?g <dnetcollectedFrom> <http://parthenos.d4science.org/handle/api_________::parthenos___::clarin::p_1271859438164> }\n"

						+ "}";

		Query query = QueryFactory.create(queryForGraphs);

		final QueryEngineHTTP serviceRequest = QueryExecutionFactory.createServiceRequest(sparqlUrl, query);

		ResultSet graphs = serviceRequest.execSelect();

		String queryForSubjectsTemplate = "SELECT DISTINCT ?s WHERE {GRAPH <%s> {?s ?p ?o}}";

		int countGraphs = 0;

		while (graphs.hasNext()) {

			countGraphs++;

			Resource g = graphs.next().getResource("g");

			System.out.println("*****GRAPH: "+g.getURI());

			final QueryEngineHTTP serviceRequest2 =

					QueryExecutionFactory.createServiceRequest(sparqlUrl, QueryFactory.create(String.format(queryForSubjectsTemplate, g.getURI())));

			ResultSet subjects = serviceRequest2.execSelect();

			int countSubjects = 0;

			while (subjects.hasNext()) {

				countSubjects++;

				Resource s = subjects.next().getResource("s");

				String describeQuery = "DESCRIBE <" + s.getURI() + ">";

				final QueryEngineHTTP serviceRequest3 = QueryExecutionFactory.createServiceRequest(sparqlUrl, QueryFactory.create(describeQuery));

				Model resultModel = serviceRequest3.execDescribe();

				serviceRequest3.close();

				resultModel.write(System.out);

			}

			serviceRequest2.close();

			System.out.println("Got "+countSubjects+" subjects");

		}

		serviceRequest.close();

		assertEquals("unexpected number of graphs", 4, countGraphs);

	}

	@Test

package eu.dnetlib.parthenos.virtuoso;

import java.io.OutputStream;

import java.util.Iterator;

import java.util.List;

import javax.annotation.Nullable;

import com.google.common.base.Function;

import com.google.common.collect.Iterators;

import com.google.common.collect.Lists;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.apache.jena.query.*;

import org.apache.jena.rdf.model.Model;

import org.apache.jena.sparql.engine.http.QueryEngineHTTP;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.web.bind.annotation.*;

/**

 * Created by Alessia Bardi on 31/01/2018.

 * Read-only API for virtuoso.

 *

 * //TODO: pagination

 * //TODO swagger documentation?

 *

 * @author Alessia Bardi

 */

@RestController

public class VirtuosoReadAPI {

	private static final Log log = LogFactory.getLog(VirtuosoReadAPI.class);

	@Value("${virtuoso.sparqlurl}")

	private String sparqlUrl;

	@Value("${virtuoso.pwd}")

	private String username;

	@Value("${virtuoso.pwd}")

	private String password;

	@Value("${virtuoso.uri.base.default}")

	private String defaultBaseURI;

	@RequestMapping(value = "/virtuoso/graphs", produces = { "application/json" }, method = RequestMethod.GET)

	public List<String> getGraphURLs(@RequestParam final String api) {

		String queryForGraphs =

				"SELECT DISTINCT ?g WHERE { { ?g <dnetcollectedFrom> <"+defaultBaseURI+api+"> }}";

		log.debug(queryForGraphs);

		Query query = QueryFactory.create(queryForGraphs);

		final QueryEngineHTTP serviceRequest = QueryExecutionFactory.createServiceRequest(sparqlUrl, query);

		ResultSet graphs = serviceRequest.execSelect();

		Iterator<String> s = Iterators.transform(graphs, new Function<QuerySolution, String>() {

			@Nullable

			@Override

			public String apply(@Nullable final QuerySolution qs) {

				return qs.getResource("g").getURI();

			}

		});

		List<String> res = Lists.newArrayList(s);

		serviceRequest.close();

		return res;

	}

	@RequestMapping(value = "/virtuoso/subjects", produces = { "application/json" }, method = RequestMethod.GET)

	public List<String> getSubjectsForGraph(@RequestParam final String graph) {

		String queryForSubjectsTemplate = "SELECT DISTINCT ?s WHERE {GRAPH <%s> {?s ?p ?o . FILTER regex(str(?s),'^http')}}";

		final QueryEngineHTTP serviceRequest =

				QueryExecutionFactory.createServiceRequest(sparqlUrl, QueryFactory.create(String.format(queryForSubjectsTemplate, graph)));

		ResultSet subjects = serviceRequest.execSelect();

		Iterator<String> s = Iterators.transform(subjects, new Function<QuerySolution, String>() {

			@Nullable

			@Override

			public String apply(@Nullable final QuerySolution qs) {

				return qs.getResource("s").getURI();

			}

		});

		List<String> res = Lists.newArrayList(s);

		serviceRequest.close();

		return res;

	}

	@RequestMapping(value = "/virtuoso/subjects/{subject}", produces = { "application/rdf+xml" }, method = RequestMethod.GET)

	public void getSubjectsForGraph(@PathVariable final String subject, final OutputStream responseStream) {

		String describeQuery = "DESCRIBE <" + subject + ">";

		final QueryEngineHTTP serviceRequest =

				QueryExecutionFactory.createServiceRequest(sparqlUrl, QueryFactory.create(describeQuery));

		Model resultModel = serviceRequest.execDescribe();

		resultModel.write(responseStream);

		serviceRequest.close();

	}

}