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https://issues.apache.org/jira/browse/JENA-1260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17556931#comment-17556931
 ] 

Andy Seaborne commented on JENA-1260:
-------------------------------------

Apache Jena 3.1.0 was released 2016-05-10. The current version is 4.5.0.

The project does not have the capacity to maintain backports.

Note that several CVEs in Jena and in Jena dependences have been addressed 
since 3.1.0.

Jena is open source and the release includes the complete repository at the 
point of release including the build setup. Anyone can download and build it 
with modifications. For trademark reasons, if you then redistribute it, you 
must rename it so as not to associate with the Apache Software Foundation.

https://git-wip-us.apache.org/repos/asf?p=jena.git;h=921853c
and test case fix:
https://github.com/apache/jena/pull/193

A modified version of 3.1.0 has no different standing from using a later 
version.


> NullPointerException when using an inferencing model under multithreaded load 
> with query and delete
> ---------------------------------------------------------------------------------------------------
>
>                 Key: JENA-1260
>                 URL: https://issues.apache.org/jira/browse/JENA-1260
>             Project: Apache Jena
>          Issue Type: Bug
>          Components: Jena
>    Affects Versions: Jena 3.0.0
>            Reporter: Stephen Owens
>            Assignee: Dave Reynolds
>            Priority: Major
>             Fix For: Jena 3.2.0
>
>         Attachments: TransitiveEngineFailureTest.java
>
>
> {noformat}
> java.lang.NullPointerException
>       at java.util.HashSet.contains(HashSet.java:203)
>       at 
> org.apache.jena.reasoner.transitiveReasoner.TransitiveEngine.triage(TransitiveEngine.java:194)
>       at 
> org.apache.jena.reasoner.transitiveReasoner.TransitiveEngine.add(TransitiveEngine.java:234)
>       at 
> org.apache.jena.reasoner.rulesys.FBRuleInfGraph.prepare(FBRuleInfGraph.java:431)
>       at 
> org.apache.jena.reasoner.BaseInfGraph.requirePrepared(BaseInfGraph.java:530)
>       at 
> org.apache.jena.reasoner.rulesys.FBRuleInfGraph.findWithContinuation(FBRuleInfGraph.java:557)
>       at 
> org.apache.jena.reasoner.rulesys.FBRuleInfGraph.graphBaseFind(FBRuleInfGraph.java:587)
>       at org.apache.jena.graph.impl.GraphBase.find(GraphBase.java:255)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIterTriplePattern$TripleMapper.<init>(QueryIterTriplePattern.java:75)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIterTriplePattern.nextStage(QueryIterTriplePattern.java:49)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIterRepeatApply.makeNextStage(QueryIterRepeatApply.java:108)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:65)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:111)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIterBlockTriples.hasNextBinding(QueryIterBlockTriples.java:63)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:111)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:39)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:111)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:39)
>       at 
> org.apache.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:111)
>       at org.apache.jena.atlas.iterator.Iter$4.hasNext(Iter.java:264)
>       at 
> org.apache.jena.ext.com.google.common.collect.Iterators$5.hasNext(Iterators.java:547)
>       at 
> org.apache.jena.test.TransitiveEngineFailureTest$FailureTask.execQuery(TransitiveEngineFailureTest.java:109)
>       at 
> org.apache.jena.test.TransitiveEngineFailureTest$FailureTask.call(TransitiveEngineFailureTest.java:75)
>       at 
> org.apache.jena.test.TransitiveEngineFailureTest$FailureTask.call(TransitiveEngineFailureTest.java:1)
>       at java.util.concurrent.FutureTask.run(FutureTask.java:266)
>       at 
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
>       at 
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
>       at java.lang.Thread.run(Thread.java:745)
> {noformat}
> This failure is due to the 
> {{org.apache.jena.reasoner.transitiveReasoner.TransitiveEngine}} class 
> declaring the {{subClassAliases}}
> member variable (of type HashSet<Node>) as static. The prepare method 
> re-creates this shared variable whenever {{isPrepared}}
> is false:
> {noformat}
>     private void prepare() {
>         if (isPrepared) return;
>         subClassAliases = new HashSet<>();
>         . . .
>         isPrepared = true;
>     }
> {noformat}
> In particular, the static {{subClassAliases}} variable will be re-created 
> whenever a {{TransitiveEngine}} object is created
> ({{isPrepared}} is false at creation time). Note that HashSet is neither 
> thread-safe nor being accessed in a thread-safe manner.
> The combination of attempting to remove triples from the model and attempting 
> to execute queries on the model leads
> to unsafe accesses to {{subClassAliases}}, which eventually leads to a null 
> pointer exception.



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