[英]Jena queryParseException
我是Jena和SPAQL的新手,嘗試使用下面的代碼在eclipse中運行jena,獲取查詢解析異常。 此查詢在http://dbpedia.org/sparql上執行良好
我想要的是出生地
例外
com.hp.hpl.jena.query.QueryParseException:第1行,第84列:未解析的前綴名稱:dbpedia-owl:birthPlace
詢問
PREFIX res: <http://dbpedia.org/resource/>
SELECT DISTINCT ?string
WHERE {
res:David_Cameron dbpedia-owl:birthPlace ?string .
}
Java代碼
import org.apache.jena.atlas.logging.Log;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QuerySolution;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.sparql.engine.http.QueryExceptionHTTP;
public class GetDateOfBirth {
private String service = null;
public GetDateOfBirth(String service)
{
this.service = service;
}
public void TestConnection(){
QueryExecution qe = QueryExecutionFactory.sparqlService(service, "ASK {}");
try{
if(qe.execAsk())
{
System.out.println(service + " is UP");
}
}catch(QueryExceptionHTTP e){
e.printStackTrace();
System.out.println(service + "is Down");
}
finally {
qe.close();
}
}
public ResultSet executeQuery(String queryString) throws Exception {
QueryExecution qe = QueryExecutionFactory.sparqlService(service, queryString);
return qe.execSelect();
}
public static void main(String[] args) {
Log.setCmdLogging() ;
String sparqlService = "http://dbpedia.org/sparql";
/*
* More query examples here:
* http://sparql.bioontology.org/examples
*/
String query = "PREFIX res: <http://dbpedia.org/resource/>" +
" SELECT ?dob WHERE { res:David_Cameron dbpedia-owl:birthPlace ?string .}";
try {
GetDateOfBirth con= new GetDateOfBirth(sparqlService);
ResultSet results = con.executeQuery(query);
for ( ; results.hasNext() ; ) {
QuerySolution soln = results.nextSolution() ;
System.out.println(soln.getResource("?dob").toString());
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
就像定義前綴PREFIX res: <http://dbpedia.org/resource/>
,您需要為dbpedia-owl
指定前綴。 使用DBPedia的Predefined Namespace Prefixes ,我假設更新的查詢將如下所示:
PREFIX res: <http://dbpedia.org/resource/>
PREFIX dbpedia-owl: <http://dbpedia.org/ontology/>
SELECT DISTINCT ?string
WHERE {
res:David_Cameron dbpedia-owl:birthPlace ?string .
}
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