A encoded query is sent via curl GET request to https://query.wikidata.org/bigdata/namespace/wdq/sparql
The resulting error message is given below. (The endpoint referenced in the service clause is Jena Fuseki 2. I've tested an analogous query against http://zbw.eu/beta/sparql/gnd/query, where it executes correctly.)
```
SPARQL-QUERY: queryStr=PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX schema: <http://schema.org/>
construct {
?gnd schema:about ?sitelink .
}
where {
service <http://zbw.eu/beta/sparql/econ_pers/query> {
?gnd skos:prefLabel [] ;
skos:exactMatch ?wd .
filter(contains(str(?wd), 'wikidata'))
}
?sitelink schema:about ?wd ;
schema:inLanguage ?language .
filter (contains(str(?sitelink), 'wikipedia'))
filter (lang(?wdLabel) = ?language && ?language in ('en', 'de'))
}
java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:188)
at com.bigdata.rdf.sail.webapp.BigdataServlet.submitApiTask(BigdataServlet.java:281)
at com.bigdata.rdf.sail.webapp.QueryServlet.doSparqlQuery(QueryServlet.java:636)
at com.bigdata.rdf.sail.webapp.QueryServlet.doGet(QueryServlet.java:278)
at com.bigdata.rdf.sail.webapp.RESTServlet.doGet(RESTServlet.java:219)
at com.bigdata.rdf.sail.webapp.MultiTenancyServlet.doGet(MultiTenancyServlet.java:214)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:808)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:577)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)
at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:110)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
at org.eclipse.jetty.server.Server.handle(Server.java:497)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:188)
at com.bigdata.rdf.sail.webapp.QueryServlet$SparqlQueryTask.call(QueryServlet.java:834)
at com.bigdata.rdf.sail.webapp.QueryServlet$SparqlQueryTask.call(QueryServlet.java:653)
at com.bigdata.rdf.task.ApiTaskForIndexManager.call(ApiTaskForIndexManager.java:68)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
... 1 more
Caused by: java.lang.NullPointerException
at com.bigdata.rdf.sparql.ast.optimizers.TypeBasedASTJoinGroupPartitionReorderer.reorderNodes(TypeBasedASTJoinGroupPartitionReorderer.java:84)
at com.bigdata.rdf.sparql.ast.optimizers.ASTJoinGroupOrderOptimizer.optimizeWithinPartition(ASTJoinGroupOrderOptimizer.java:455)
at com.bigdata.rdf.sparql.ast.optimizers.ASTJoinGroupOrderOptimizer.optimizeWithinPartitions(ASTJoinGroupOrderOptimizer.java:333)
at com.bigdata.rdf.sparql.ast.optimizers.ASTJoinGroupOrderOptimizer.optimizeJoinGroup(ASTJoinGroupOrderOptimizer.java:144)
at com.bigdata.rdf.sparql.ast.optimizers.AbstractJoinGroupOptimizer.optimize(AbstractJoinGroupOptimizer.java:161)
at com.bigdata.rdf.sparql.ast.optimizers.AbstractJoinGroupOptimizer.optimize(AbstractJoinGroupOptimizer.java:101)
at com.bigdata.rdf.sparql.ast.optimizers.ASTOptimizerList.optimize(ASTOptimizerList.java:117)
at com.bigdata.rdf.sparql.ast.eval.AST2BOpUtility.convert(AST2BOpUtility.java:262)
at com.bigdata.rdf.sparql.ast.eval.ASTEvalHelper.evaluateGraphQuery(ASTEvalHelper.java:525)
at com.bigdata.rdf.sail.BigdataSailGraphQuery.evaluate(BigdataSailGraphQuery.java:115)
at com.bigdata.rdf.sail.BigdataSailGraphQuery.evaluate(BigdataSailGraphQuery.java:97)
at org.openrdf.repository.sail.SailGraphQuery.evaluate(SailGraphQuery.java:113)
at com.bigdata.rdf.sail.webapp.BigdataRDFContext$GraphQueryTask.doQuery(BigdataRDFContext.java:1774)
at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.innerCall(BigdataRDFContext.java:1567)
at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.call(BigdataRDFContext.java:1532)
at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.call(BigdataRDFContext.java:704)
... 4 more
```