I'm wondering how familiar you are with Java, SPARQL and the like. You
are quite often posting errors which are solvable if looking more
carefully on the code and query:
In your query there is no ?abstract variable. Moreover, it's better to
use just the variable name without the question mark, i.e., in your
example just abstract instead of ?abstract.
As a sidenote, your query is looking for the English labels of countries
of the resource http://dbpedia.org/resource/Quatre_Bornes.
On 29.02.2016 19:23, kumar rohit wrote:
I am sorry Lorenz sir, here is the code.
String service = "http://dbpedia.org/sparql";;
String query = "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')"+
"}";
QueryExecution qe = QueryExecutionFactory.sparqlService(service, query);
try {
ResultSet results = qe.execSelect();
for (; results.hasNext();) {
QuerySolution sol = (QuerySolution) results.next();
System.out.println(sol.get("?abstract"));
}
}catch(Exception e){
e.printStackTrace();
}
finally {
qe.close();
}
}
On Mon, Feb 29, 2016 at 3:19 PM, Lorenz B. <
[email protected]> wrote:
And how can somebody help you without seeing the code? And where NULL is
returned.
I think it was the problem of not including the right prefix. I included
it, the error goes away but it just ouput "null". I do not know why, but
it
gives me the result at SPARQL endpoint, but in Jena, it shows null as
output.
On Mon, Feb 29, 2016 at 12:30 PM, Andy Seaborne <[email protected]> wrote:
What have you tried?
Before firing off questions, try to solve basic java issues using google,
stackoverflow etc.
Caused by: java.net.UnknownHostException: dbpedia.org
so it's a networking issue in your environment.
Firewall, misconfigured DNS etc.
Study the output of
nslookup dbpedia.org
Andy
On 29/02/16 11:29, Lorenz B. wrote:
It has to be http://dbpedia.org/sparql
Hello I am getting this exception when I run jena against dbpedia.
What is
the problem?
++++++++++++++++++++++++++++++++++
:WARN No appenders could be found for logger
(org.apache.jena.riot.system.stream.JenaIOEnvironment).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig
for
more info.
HttpException: java.net.UnknownHostException: dbpedia.org: Unexpected
error
making the query: java.net.UnknownHostException: dbpedia.org
at
com.hp.hpl.jena.sparql.engine.http.HttpQuery.rewrap(HttpQuery.java:417)
at
com.hp.hpl.jena.sparql.engine.http.HttpQuery.execGet(HttpQuery.java:358)
at
com.hp.hpl.jena.sparql.engine.http.HttpQuery.exec(HttpQuery.java:295)
at
com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP.execResultSetInner(QueryEngineHTTP.java:346)
at
com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP.execSelect(QueryEngineHTTP.java:338)
at jenaclass.main(jenaclass.java:24)
Caused by: java.net.UnknownHostException: dbpedia.org
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(Unknown Source)
at java.net.InetAddress.getAddressesFromNameService(Unknown Source)
at java.net.InetAddress.getAllByName0(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at
org.apache.http.impl.conn.SystemDefaultDnsResolver.resolve(SystemDefaultDnsResolver.java:45)
at
org.apache.http.impl.conn.DefaultClientConnectionOperator.resolveHostname(DefaultClientConnectionOperator.java:278)
at
org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:162)
at
org.apache.http.impl.conn.ManagedClientConnectionImpl.open(ManagedClientConnectionImpl.java:294)
at
org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:643)
at
org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:479)
at
org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:906)
at
org.apache.http.impl.client.DecompressingHttpClient.execute(DecompressingHttpClient.java:137)
at
org.apache.http.impl.client.DecompressingHttpClient.execute(DecompressingHttpClient.java:118)
at org.apache.jena.riot.web.HttpOp.exec(HttpOp.java:1108)
--
Lorenz Bühmann
AKSW group, University of Leipzig
Group: http://aksw.org - semantic web research center
