[rules-users] How to design a rule using collect for filtering? Thanks.

[Anh Vuong]

Thanks for your help, Edson. 
  collect works in my simple test now, but not when I integrate with my code. Is there an easy way to debug LHS to see if collect stmt is evaluated?  I notice IllegalAccessError
 since my app will load a selected list of jars upfront, so my questions are:
  1) Can this error break collect?
  2) How can I fix this error still using our own classLoader?
   
  Here is the stack trace:
  2007 Aug 15, 09:08:13:193        Exception IllegalAccessError
java.lang.IllegalAccessError: class org.drools.reteoo.InitialFactImplShadowProxy cannot access its superclass org.drools.reteoo.Init
ialFactImpl
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at org.drools.rule.MapBackedClassLoader.fastFindClass(MapBackedClassLoader.java:60)
        at org.drools.rule.MapBackedClassLoader.loadClass(MapBackedClassLoader.java:79)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at org.drools.reteoo.Rete$ObjectTypeConf.loadOrGenerateProxy(Rete.java:379)
        at org.drools.reteoo.Rete$ObjectTypeConf.defineShadowProxyData(Rete.java:344)
        at org.drools.reteoo.Rete$ObjectTypeConf.<init>(Rete.java:320)
        at org.drools.reteoo.Rete.assertObject(Rete.java:145)
        at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:190)
        at org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction.execute(ReteooWorkingMemory.java:163)
        at org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1241)
        at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:858)
        at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:822)
        at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:623)

   
  Thanks,
  -av
   
  
Edson Tirelli <tirelli at post.com> wrote:
  
   No single simple answer here. You need to check what would better fit your use case. 
   The thing is: it is not possible to limit the number of matches to a collect statement... all matching instances WILL match it and be collected. 

   No really "clean" way I can think about, but a few possible options (haven't executed them, but shall work):

1. Simply execute the actions multiple times in the consequence:

  when 
     eventList : LinkedList( $size : size >= 5 ) from collect( Event(text matches ".*rule5.*" )) 
then
   for( int i = 0; i < $size/5; i++ )

         System.out.println("rule5 is fired " + eventList.size ()); 

end

2. Flag used facts:

  when
     eventList : LinkedList( size >= 5 ) from collect( Event(text matches ".*rule5.*", processed == false )) 
then
   System.out.println("rule5 is fired " + eventList.size()); 
   for( int i = 0; i < 5; i++ ) {
       Event e = (Event) eventList.get ( i );
       e.setProcessed( true );
       update( e ); 

     }

end

2. Retract used facts:

  when
     eventList : LinkedList( size >= 5 ) from collect( Event(text matches ".*rule5.*" )) 
then
   System.out.println("rule5 is fired " + eventList.size()); 
   for( int i = 0; i < 5; i++ ) {
       Event e = (Event) eventList.get( i ); 
       retract( e ); 

     }

end

    Hope it helps.

    Edson

  2007/8/10, Anh Vuong <anhtvuong at yahoo.com>:    Hi,
  I'd like to use keyword collect to do my filtering but its behaviour confused me, please advise. I greatly appreciate your help.
   
  Problem 1:
   
  when 
  eventList : LinkedList(size == 5)
  from collect( Event(text matches 
".*rule5.*" ))   
  
then   System.out.println(
"rule5 is fired " + eventList.size());    
  I still do not see any log msg after adding 5+ events. Is something wrong with my rule?
   
  Problem 2:
   
  when
  event: Event(text matches ".*rule5.*" ))
  eventList : LinkedList(size == 5)
  from collect( Event(text == event.text)
  
  
then   System.out.println(
"rule5 is fired " + eventList.size());    
  After adding 5 events, I see 5 log msg instead of one as I'd expect. 
  If I add more events, I will see more log. How do I tell LHS  to reset the count from 0.
  Basically, I want to take 1 event out of 5 similar events (suppressing filtering). So if there are 10 similar events, my RHS should activate 2 times, not 10 times. 
   
  Thanks,
  -av
   
  
  
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-- 
  Edson Tirelli
  Software Engineer - JBoss Rules Core Developer
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
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