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https://issues.apache.org/jira/browse/JENA-824?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14235382#comment-14235382
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Kristian Rosenvold commented on JENA-824:
-----------------------------------------
Yup, I was thinking about something like that. I have tested calling
setResultVars manually after creation here on my project and it fixes the
problem.
The second part of the patch I was looking at was basically to set a "sealed"
flag on the Query once this is done and actually fail all the setters if they
are called after the object has been sealed. I'm still trying to find out if
that will work.
I'll see if I can get some hours on this in the weekend.
> Concurrent usage of query causes NPE
> ------------------------------------
>
> Key: JENA-824
> URL: https://issues.apache.org/jira/browse/JENA-824
> Project: Apache Jena
> Issue Type: Bug
> Reporter: Kristian Rosenvold
>
> Callin gQueryFactory.parse and then handling the Query off to multiple
> threads can/will cause the error show in the stacktrace.
> As long as setResultVars is called on the Query before handing off to
> threads, it seems to be safe.
> Pull request is coming on this.
> java.lang.NullPointerException
> at com.hp.hpl.jena.sparql.core.Var.varNames(Var.java:193)
> at com.hp.hpl.jena.query.Query.getResultVars(Query.java:369)
> at
> com.hp.hpl.jena.sparql.engine.QueryExecutionBase.asResultSet(QueryExecutionBase.java:470)
> at
> com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execResultSet(QueryExecutionBase.java:533)
> at com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execSelect
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