[rules-users] npe in LogicalRetractCallback when using jpa persistence

[Edson Tirelli]

    Chris,

    I will look into this problem, but I am not sure how to reproduce it.
Maybe you can provide me a test case? If so, please open a JIRA, attached
your test case and ping me.

    Thanks,
        Edson


2010/8/10 Chris Raschl <c.raschl at dyless.com>

> Hi,
> Just in case someone faces the same problem, comments inline:
>
> Am 05.08.2010 13:53, schrieb Chris Raschl:
> > I'm using the latest drools and drools flow snapshot with jpa
> persistence.
> >
> > When I'm retracting a fact from the knowledge session (which causes
> > logical retraction), the session can't be persisted any more.
> >
> > During retraction a LogicalRetractCallback is instantiated using this
> > constructor:
> >
> > public LogicalRetractCallback(final TruthMaintenanceSystem tms,
> >                                 final LogicalDependency node,
> >                                 final Set set,
> >                                 final InternalFactHandle handle,
> >                                 final PropagationContext context,
> >                                 final Activation activation) {
> >       this.tms = tms;
> >       this.node = node;
> >       this.set = set;
> >       this.handle = handle;
> >       this.context = context;
> > }
> >
> > As you can see an activation object can be passed (and actually is
> > passed) to the constructor, but is never used. Retraction works though.
> >
> > The problem occurs when the knowledge session is persisted, because
> > LogicalRetractCallback.write assumes that activation is not null, which
> > leads to this npe:
> >
> > Caused by: java.lang.NullPointerException
> >
> org.drools.common.TruthMaintenanceSystem$LogicalRetractCallback.write(TruthMaintenanceSystem.java:251)
> >
> org.drools.marshalling.impl.OutputMarshaller.writeActionQueue(OutputMarshaller.java:201)
>
> Adding this.activation = activation to the constructor does not help,
> beause the npe in the write method remains. I tried it, then the whole
> expression "context.terminalTupleMap.get( this.activation.getTuple() )"
> in the write method evaluates to null...
>
> I found out persistence was triggered by an unneccessary flush in my
> code. I removed that, everything works now.
>
> That seems to be the case because the action queue is empty then and
> there's no need to persist it, thus the write method is never called. I
> guess the problem remains if someone tries to persist a session with an
> action queue containing a LogicalRetractCallback object.
>
> - chris
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>



-- 
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com
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