[英]DBpedia Jena Query returning null
我只是想在 DBpedia 上運行一個小查詢,查詢本身可以工作,請在此處查看,但我不知道為什么在使用 Jena 執行此操作時它會返回,我得到了空值。
String service = "http://dbpedia.org/sparql";
String queryString = "";
queryString = "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> SELECT ?label" +
"WHERE {" +
"<http://dbpedia.org/resource/Quatre_Bornes> <http://dbpedia.org/ontology/country> ?y ."+
"?y rdfs:label ?label ."+
"FILTER (LANG(?label) = 'en')"+
"}";
Query query = QueryFactory.create(queryString);
QueryEngineHTTP qexec = QueryExecutionFactory.createServiceRequest(service, query);
ResultSet results = qexec.execSelect();
for ( ; results.hasNext() ; ) {
QuerySolution soln = results.nextSolution() ;
System.out.println(soln.getLiteral("label"));
}
有什么建議嗎?
太尷尬了,查詢中存在空間問題:
String service = "http://dbpedia.org/sparql";
String queryString = "";
queryString = "PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> SELECT ?label " +
"WHERE {" +
"<http://dbpedia.org/resource/Quatre_Bornes> <http://dbpedia.org/ontology/country> ?y ."+
"?y rdfs:label ?label ."+
"FILTER (LANG(?label) = 'en')"+
"}";
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