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

[Mark Proctor]

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
>
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