Re: Problem of querying dbpedia endpoint

[Andy Seaborne]

On 09/07/11 00:06, 朱曼 wrote:
Dear list,

hi~~

I encounter "HttpException: java.net.SocketException: Connection reset:
java.net.SocketException: Connection reset" exception when I run the
following code, could you help me?

Usually a timeout at DBpedia.


         try {
             Model dbpedia_model = ModelFactory.createDefaultModel();
             String queryStr = "SELECT distinct ?c WHERE { ?c a owl:Class }";
             Query query = QueryFactory.create(queryStr);

This is not the code you are running - that would lead to a parse error 
at this point.  owl: is not defined.

             query.addGraphURI("http://dbpedia.org/";);

This is the same as adding FROM to the query. You do not use it for 
DBpedia.  Remove this.

             QueryExecution qexec = QueryExecutionFactory.sparqlService("
http://dbpedia.org/sparql";, query);
             ResultSet rs = qexec.execSelect();
             ResultSetFormatter.out(System.out, rs, query);
             qexec.close();
         } catch (Exception e) {
             e.printStackTrace();
         }

all the best

June


Works for me:

try {
    Model dbpedia_model = ModelFactory.createDefaultModel();
    String queryStr = "select distinct ?Concept where {[] a ?Concept} 
LIMIT 10";
    Query query = QueryFactory.create(queryStr);
    QueryExecution qexec = 
QueryExecutionFactory.sparqlService("http://dbpedia.org/sparql";, query);
    // Set the DBpedia specific timeout.
    ((QueryEngineHTTP)qexec).addParam("timeout", "10000") ;
    ResultSet rs = qexec.execSelect();
    ResultSetFormatter.out(System.out, rs, query);
    qexec.close();
   } catch (Exception e) {
      e.printStackTrace();
        }

        Andy