Andy, In addition I am working in another end point, and now I am getting this output:
Endpoint returned Content-Type: text/html which is not rcognized for SELECT queries I followed this recommendation https://stackoverflow.com/questions/41926530/jena-endpoint-returned-content-type-text-html however the behavior does not change, and I continue receiving this error: Exception in thread "main" org.apache.jena.query.QueryException: Endpoint returned Content-Type: text/html which is not rcognized for SELECT queries at org.apache.jena.sparql.engine.http.QueryEngineHTTP.execResultSetInner(QueryEngineHTTP.java:377) at org.apache.jena.sparql.engine.http.QueryEngineHTTP.execSelect(QueryEngineHTTP.java:345) at ag.pst.jena.test.RDFConnectionExample4.main(RDFConnectionExample4.java:84) any recommendation? Luis El jue., 9 abr. 2020 a las 15:03, Andy Seaborne (<[email protected]>) escribió: > > "SELECT ?item1 WHERE {\n" + > > " ?item1 wdt:P31 ?item2.\n" + > > "} LIMIT 10"; > > > > qs1.getResource("s") > > The variable is called "item1" > > qs1.getResource("item1") > > Andy > > On 09/04/2020 13:47, Luis Enrique Ramos García wrote: > > dear member of jena community, > > > > I have been trying to query wikidata following the documentation [1] and > > other examples I have found, but result obtained has been null values, > > besides it is a simple query, that I have just previously tested in the > > wikidata query GUI. > > > > I followed two methods, one with QueryExecution, and another > > with RDFConnectionRemote, but however in both the output is null as well. > > > > Please, let me know if I am missing something, or if I am going in the > > wrong direction. > > > > > > Best regards > > > > > > > > Luis Ramos > > > > > > *CODE * > > > > > > > > import org.apache.jena.query.Query; > > import org.apache.jena.query.QueryExecution; > > import org.apache.jena.query.QueryExecutionFactory; > > import org.apache.jena.query.QueryFactory; > > import org.apache.jena.query.QuerySolution; > > import org.apache.jena.query.ResultSet; > > import org.apache.jena.rdf.model.Resource; > > import org.apache.jena.rdfconnection.RDFConnection; > > import org.apache.jena.rdfconnection.RDFConnectionFactory; > > import org.apache.jena.rdfconnection.RDFConnectionRemote; > > import org.apache.log4j.BasicConfigurator; > > import org.apache.log4j.Level; > > import org.apache.log4j.Logger; > > > > > > > > > > /* > > * Example of a building a remote connection. > > > > */ > > public class RDFConnectionExample4 { > > > > //testing > > static Logger log = Logger.getLogger(RDFConnectionExample4.class); > > > > > > > > > > public static void main(String ...args) { > > > > log.setLevel(Level.INFO); > > log.info("This is Luis Logger"); > > BasicConfigurator.configure(); > > > > > > > > String my_query = "PREFIX schema: <http://schema.org/>\n" + > > "PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>\n" + > > "PREFIX owl: <http://www.w3.org/2002/07/owl#>\n" + > > "PREFIX hist: <http://wikiba.se/history/ontology#>\n" + > > "PREFIX wd: <http://www.wikidata.org/entity/>\n" + > > "PREFIX wdt: <http://www.wikidata.org/prop/direct/>\n" + > > "PREFIX wikibase: <http://wikiba.se/ontology#>\n" + > > "PREFIX dct: <http://purl.org/dc/terms/>\n" + > > "\n" + > > "SELECT ?item1 WHERE {\n" + > > " ?item1 wdt:P31 ?item2.\n" + > > "} LIMIT 10"; > > > > System.out > > > > .println("The query string is"+ my_query); > > > > Query query = QueryFactory.create(my_query); > > > > //method 1 with query execution > > > > QueryExecution qe1 = QueryExecutionFactory.sparqlService(" > > https://query.wikidata.org/sparql";, query); > > > > ResultSet rs1 = qe1.execSelect() ; > > > > while(rs1.hasNext()) { > > QuerySolution qs1 = rs1.next() ; > > Resource subject1 = qs1.getResource("s") ; > > System.out.println("Subject: "+subject1) ; > > } > > > > //method 2 > > > > > > > > > > RDFConnection conn0 = RDFConnectionRemote.create() > > .destination("https://query.wikidata.org/";) > > .queryEndpoint("sparql") > > // Set a specific accept header; here, sparql-results+json > > (preferred) and text/tab-separated-values > > //The default is "application/sparql-results+json, > > application/sparql-results+xml;q=0.9, text/tab-separated-values;q=0.7, > > text/csv;q=0.5, application/json;q=0.2, application/xml;q=0.2, */*;q=0.1" > > .acceptHeaderSelectQuery("application/sparql-results+json, > > application/sparql-results+xml;q=0.9") > > .build(); > > > > > > String queryService = "https://query.wikidata.org/sparql?";; > > > > RDFConnection conn = RDFConnectionFactory.connect(queryService, > > null, null); > > > > QueryExecution qe2 = conn.query(query); > > > > ResultSet rs2 = qe2.execSelect() ; > > > > while(rs2.hasNext()) { > > QuerySolution qs2 = rs2.next() ; > > Resource subject2 = qs2.getResource("s") ; > > System.out.println("Subject: "+subject2) ; > > } > > > > > > > > // QueryExecution qExec = conn.query(query); > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > > > https://jena.apache.org/documentation/rdfconnection/ > > >
