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

[Chris West]

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
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