[rules-users] The effect of not using shadow facts

Tue Jul 17 22:24:51 EDT 2007

   Chris,

   I found and developed an intermediate solution that shall work for your
proxies.
   If it is not possible to create a shadow fact for a class that is
asserted (because the class is final or whatever), the engine goes up in the
class hierarchy, looking for a class or interface for which is possible to
create the proxy, but that still matches all ObjectTypes available in the
rule base matched by the original class. The analysis is a bit complex,
specially because new rules with new object types can be dynamically added
to the rule base, but I believe the solution will work for JDK proxies and
the most common proxy frameworks out there, that usually don't proxy
multiple unrelated interfaces at once.

   So, I ask you please to get latest snapshot from the repository and try
it out for your use case and report back to the list the results, since
seems there are a few other people using similar things.

    Thanks,
        Edson

2007/7/17, Chris West <crayzfishr at gmail.com>:
>
> Is that still true if the equals() and hashcode() methods are only based
> on the identity fields of the object (which cannot change)?
>
> -Chris West
>
> On 7/17/07, Mark Proctor <mproctor at codehaus.org> wrote:
> >
> >  you only need to use modifyRetract if the object is inserted. The
> > reason for this is if you change field values on your facts we will not be
> > able to remove them from our various internal hashmaps; thus the need to
> > remove first prior to any changes, then make the changes and then insert it
> > again. We can't allow users to just call update() as we have no idea what
> > the old values where, thus we cannot find the objects in our hashmaps.
> >
> > Mark
> > Chris West wrote:
> >
> > Mark,
> >
> > Using modifyRetract and modifyInsert seems to fix the problem (at least
> > in my test case I finally created).  I'll try this on my real code.
> >
> > My only concern here is that it puts the burden on the rule author to
> > know whether things are being shadowed or not.  For shadowing that is
> > explicitly turned off this is ok.  But for implicit non-shadowing based on a
> > class being final, this is not at all obvious to the rule auther.
> >
> > Is there any way to have this hidden such that I can still call "update"
> > but have it use "modifyRetract" and "modifyInsert" instead?
> >
> > Also, I'm curious why I have to call modifyRetract before I start
> > modifing the object, since the engine does not know about my modifications
> > anyway until I call update or modifyInsert?  By the way, I was unable to use
> > the block setter approach in the rule consequence due to not having set
> > methods for modifying my objects.
> >
> > Thanks,
> > -Chris West
> >
> > On 7/17/07, Mark Proctor <mproctor at codehaus.org > wrote:
> > >
> > > If you do not have shadow facts you cannot use the update() method, it
> > > will leave the working memory corrupted. Instead you must manage this
> > > yourself, before you change any values on the object you must call
> > > modifyRetract() and after you hvae finished your changes ot hte object call
> > > modifyInsert() - luckily if you are doing this in the consequence you can
> > > use the MVEL modify keyword combined with the block setter and it does this
> > > for you:
> > > modify ( person ) { age += 1, location = "london" }
> > >
> > > Mark
> > > Chris West wrote:
> > >
> > > Hello,
> > >
> > > With prior versions of JBoss Rules (3.0.5) I have been using JDK
> > > generated dynamic proxies as facts, and they have been working fine.
> > > However, after upgrading to JBoss Rules 4.0.0MR3, I cannot seem to get
> > > the dynamic proxies to work as facts.  It seems that even though a rule
> > > fires that changes a field on the proxy, a second rule that should not be
> > > activated after the update still fires.
> > >
> > > According to the JDK javadoc documentation, dynamic proxies are
> > > created as final.  My assumption is that JBoss Rules is not creating Shadow
> > > facts for these since they are final.  After reading the JIRA at
> > > http://jira.jboss.com/jira/browse/JBRULES-960, I now am questioning
> > > what the effect of not using shadow facts is on the engine.  The relevant
> > > part of that is:
> > >
> > > "The problem is that SpringAOP is generating a proxy whose methods
> > > equals() and hashCode() are "final". As drools must either override these
> > > methods in the shadow proxy or not shadow the fact at all, I'm disabling
> > > shadow proxy generation for this use case.
> > > It is really important to note that if you are asserting SpringAOP
> > > proxies as facts into the working memory, you will not be able to change any
> > > field value whose field is constrained in rules or you may incur in a memory
> > > leak and non-deterministic behavior by the rules engine. Unfortunately there
> > > is nothing we can do about, since when SpringAOP makes the methods equals
> > > and hashcode final, we can't override them anymore and as so, we can't
> > > shadow them."
> > >   [ Show » <http://jira.jboss.com/jira/browse/JBRULES-960> ]
> > >   Edson Tirelli<http://jira.jboss.com/jira/secure/ViewProfile.jspa?name=tirelli>
> > > [02/Jul/07 03:29 PM] The problem is that SpringAOP is generating a
> > > proxy whose methods equals() and hashCode() are "final". As drools must
> > > either override these methods in the shadow proxy or not shadow the fact at
> > > all, I'm disabling shadow proxy generation for this use case. It is really
> > > important to note that if you are asserting SpringAOP proxies as facts into
> > > the working memory, you will not be able to change any field value whose
> > > field is constrained in rules or you may incur in a memory leak and
> > > non-deterministic behavior by the rules engine. Unfortunately there is
> > > nothing we can do about, since when SpringAOP makes the methods equals and
> > > hashcode final, we can't override them anymore and as so, we can't shadow
> > > them.
> > >
> > > Although I'm not using SpringAOP, I believe my facts are not being
> > > shadowed.
> > >
> > > Is it true that not using shadow facts may lead to non-deterministic
> > > behavior?  Prior to shadow facts, the engine seemed to handle it.  Any
> > > chance of reverting back to the old style of truth maintenance in the case
> > > of not using shadow facts.
> > >
> > > I apologize if I'm not on the right track here.  My only test case for
> > > my problem is the entire application right now, so I cannot offer it for
> > > discussion.  Any advice would be greatly appreciated.
> > >
> > > Thanks,
> > > -Chris West
> > >
> > >  ------------------------------
> > >
> > > _______________________________________________
> > > rules-users mailing list
> > > rules-users at lists.jboss.org
> > >
> > > https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> > >
> > > _______________________________________________
> > > rules-users mailing list
> > > rules-users at lists.jboss.org
> > > https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> > ------------------------------
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>

-- 
  Edson Tirelli
  Software Engineer - JBoss Rules Core Developer
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
  JBoss, a division of Red Hat @ www.jboss.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-users/attachments/20070717/b687594a/attachment.html 