[jira] [Created] (JENA-940) SPARQL SERVICE Query against dbpedia.org doesnt work

["Robert Mercer (JIRA)" <ji...@apache.org>]

Robert Mercer created JENA-940:
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             Summary: SPARQL SERVICE Query against dbpedia.org doesnt work
                 Key: JENA-940
                 URL: https://issues.apache.org/jira/browse/JENA-940
             Project: Apache Jena
          Issue Type: Bug
    Affects Versions: Jena 2.13.0, Jena 2.11.0
            Reporter: Robert Mercer


I've specified Affects versions against the version of Jena that I've tested, although it looks like it affects all versions of Jena.

Basically it boils down to this, if you specify dbpedia.org in a SERVICE query now you receive an error message with the following stack trace:

com.hp.hpl.jena.sparql.resultset.ResultSetException: Failed when initializing the StAX parsing engine
at com.hp.hpl.jena.sparql.resultset.XMLInputStAX.<init>(XMLInputStAX.java:118)
at com.hp.hpl.jena.sparql.resultset.XMLInput.make(XMLInput.java:73)
at com.hp.hpl.jena.sparql.resultset.XMLInput.fromXML(XMLInput.java:42)
at com.hp.hpl.jena.sparql.resultset.XMLInput.fromXML(XMLInput.java:37)
at com.hp.hpl.jena.query.ResultSetFactory.fromXML(ResultSetFactory.java:321)
at com.hp.hpl.jena.sparql.engine.http.Service.exec(Service.java:117)
at com.hp.hpl.jena.sparql.engine.main.iterator.QueryIterService.nextStage(QueryIterService.java:51)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.makeNextStage(QueryIterRepeatApply.java:113)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:65)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIterConvert.hasNextBinding(QueryIterConvert.java:59)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:40)
at com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:108)
at com.hp.hpl.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:72)
at org.topbraidcomposer.sparql.view.SPARQLView$8.handleResultSet(SPARQLView.java:371)
at org.topbraidcomposer.sparql.view.SPARQLView$10.runSelectOrDescribe(SPARQLView.java:470)
at org.topbraidcomposer.sparql.view.SPARQLView$10.run(SPARQLView.java:439)
at org.topbraidcomposer.core.util.ThreadUtil$1$1.run(ThreadUtil.java:64)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at com.sun.org.apache.xerces.internal.impl.XML11NSDocumentScannerImpl.scanStartElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XML11NSDocumentScannerImpl.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLStreamReaderImpl.next(Unknown Source)
at com.hp.hpl.jena.sparql.resultset.XMLInputStAX$ResultSetStAX.processHead(XMLInputStAX.java:387)
at com.hp.hpl.jena.sparql.resultset.XMLInputStAX$ResultSetStAX.init(XMLInputStAX.java:197)
at com.hp.hpl.jena.sparql.resultset.XMLInputStAX$ResultSetStAX.<init>(XMLInputStAX.java:189)
at com.hp.hpl.jena.sparql.resultset.XMLInputStAX.worker(XMLInputStAX.java:148)
at com.hp.hpl.jena.sparql.resultset.XMLInputStAX.<init>(XMLInputStAX.java:111)
... 21 more 

This is because dbpedia.org recently upgraded to XML 1.1 from 1.0 and apparently the XercesImpl that is packaged with Jena doesnt support this, which is the core issue.

Case 1. Here's a query using SERVICE against the normal DBpedia endpoint. It fails with the StAX exception. (empty.ttl is an empty file.)

sparql --data empty.ttl "SELECT * { SERVICE <http://dbpedia.org/sparql> { ?s ?p ?o } } LIMIT 1"

Case 2. Here's a remote SPARQL query against the normal endpoint (so Jena doesn't evaluate the query at all, but sends the complete query to the endpoint, and only parses the results). It succeeds.

rsparql --service=http://dbpedia.org/sparql "SELECT * { ?s ?p ?o } LIMIT 1"

So it looks like Jena is doing something differently between cases 1 and 2 in the way it sends the query or handles the results.




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