In fact in your case you when condition doesn’t make any sense – B will never equal the empty string as B isn’t a string.

You probable want the following:

rule “foo”

when
   $a :A(Type == "Prod" , objectB == null)
then
   B bobject = new B();

   bobject.setType(“Prod”);

   bobject.setId($a.getNumber().getId());

   modify($a) {

      setObjectB(bobject);

    };

end

 

This rule only executes when objectB  is null, this means you won’t get into the loop as once you have created objectB  the rule won’t evaluate to true again.

 

Thomas



From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Esteban Aliverti
Sent: 03 June 2010 23:43
To: Rules Users List
Subject: Re: [rules-users] Object Referencing Error

 

Yes, your rule entered in an infinite loop because when every time you insert/modify/retract a Fact, rules are reevaluated to check if the insertion/modification/retraction generates activations or not. In your case, your rule is being reevaluated every time you update your $a object, the evaluation ends firing the rule, and this starts an endless loop. 

If you only have this behavior with this rule, you can consider using the "no-loop" attribute. If your problem is multiple rules being re executed (and you don't wont that) you can use "lock-on-active" attribute. Try to read the documentation about these attributes for further information. 

It is very important for the people new in drools to understand the life cycle of a rule.

 

Best,  

On Thu, Jun 3, 2010 at 7:33 PM, Fnu Mahalakshmi <FMahalakshmi@nyx.com> wrote:

Hi,

I tried what you said but program goes into an infinite loop.
It does not break out of the when loop only.
I did exactly as you mentioned.
In the test information I put in a.type = "Prod"
And a.bObject(new B());
Any idea whats wrong??

Thanks,
M

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Subject: rules-users Digest, Vol 43, Issue 15

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Today's Topics:

  1. Re: Object Referencing error: (Esteban Aliverti)


----------------------------------------------------------------------

Message: 1
Date: Thu, 3 Jun 2010 17:51:10 -0300
From: Esteban Aliverti <esteban.aliverti@gmail.com>
Subject: Re: [rules-users] Object Referencing error:
To: Rules Users List <rules-users@lists.jboss.org>
Message-ID:
       <AANLkTimeZIJ5VfMTBESLFJIWoc_4MEZSXbKMIXAvJRiC@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

You can't modify bobject, becuase it doesn't exist inside the session. You
just created it a few lines above. Maybe you need an insert() or maybe you
need the bobject reference from the LHS. Something like this:

*rule* "prod"



     *when*

        $a :A(Type == "Prod" , objectB != "")

     *then*

  B bobject = *new* B();

        $a.getObjectB().setType( "Prod" );

        $a.getObjectB().setId($a.getNumber().getId());

        *update*($a);

*      end*

Note that you need to update $a and not B, because A is the inserted Fact in
your session.

Best,


2010/6/3 Fnu Mahalakshmi <FMahalakshmi@nyx.com>

>  Hi,
>
>
>
> I am getting the following error when I try to do complex object
> referencing in drools:
>
> My class:
>
> A{
>
> String Type;
>
> B objectb;
>
> //getters and setters for above
>
> }
>
>
>
> My rules:
>
>
>
> *rule* "prod"
>
>
>
>       *when*
>
>      $a :A(Type == "Prod" , objectB != "")
>
>       *then*
>
> B bobject = *new* B();
>
>      bobject.setType( "Prod" );
>
>      bobject.setId($a.getNumber().getId());
>
>      *update*(bobject);
>
>
>
> *end*
>
> * *
>
> *I want to basically output a file which has updated values of B (type,
> Id)
>
> *
>
> * *
>
> *Error:*
>
> *org.drools.spi.ConsequenceException*: *org.drools.FactException*: Update
> error: handle not found for object: com.org.Ip@f42ad0. Is it in the
> working memory?
>
>       at
> org.drools.base.DefaultConsequenceExceptionHandler.handleException(*
> DefaultConsequenceExceptionHandler.java:13*)
>
>       at org.drools.common.DefaultAgenda.fireActivation(*
> DefaultAgenda.java:558*)
>
>       at org.drools.common.DefaultAgenda.fireNextItem(*
> DefaultAgenda.java:518*)
>
>       at org.drools.common.AbstractWorkingMemory.fireAllRules(*
> AbstractWorkingMemory.java:475*)
>
>       at org.drools.common.AbstractWorkingMemory.fireAllRules(*
> AbstractWorkingMemory.java:439*)
>
>       at com.org.DroolsTest.main(*DroolsTest.java:30*)
>
> Caused by: *org.drools.FactException*: Update error: handle not found for
> object: com.org.Ip@f42ad0. Is it in the working memory?
>
>       at org.drools.base.DefaultKnowledgeHelper.update(*
> DefaultKnowledgeHelper.java:100*)
>
>       at com.org.Rule_Prod_Ip_0.consequence(*Rule_Prod_Ip_0.java:10*)
>
>       at com.org.Rule_Prod_Ip_0ConsequenceInvoker.evaluate(*
> Rule_Prod_Ip_0ConsequenceInvoker.java:22*)
>
>       at org.drools.common.DefaultAgenda.fireActivation(*
> DefaultAgenda.java:554*)
>
>       ... 4 more
>
>
>
> Please help! I am very new to drools! Not able to figure out why this
> error:
>
>
>
> I am using eclipse and working on Windows machine. Error above was
> generated on eclipse console.
>
>
>
> Thank you.
>
>
>
> M
>
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