[rules-users] Unable to access a property of a query parameter in the query constraint (Drools 4.0.7)

[Przemysław Różycki]

Hello,

I found some confusing thing while constructing queries.
Let's assume I have a simple model with 2 classes:

public static class Product {
   private BigInteger productId;

   public Product(int id) {
     productId = BigInteger.valueOf((long)id);
   }

   public void setProductId(BigInteger productId) {
     this.productId = productId;
   }

   public BigInteger getProductId() {
     return productId;
   }
}
	
public static class Relation {
   private BigInteger productAID;
   private Product productB;

   public void setProductAID(BigInteger productAID) {
     this.productAID = productAID;
   }

   public BigInteger getProductAID() {
     return productAID;
   }

   public void setProductB(Product productB) {
     this.productB = productB;
   }

   public Product getProductB() {
     return productB;
   }
}

It's not very sophisticated.

And I have a query:

query "Query_1" (Product $p)
   $r : Relation( productAID == $p.productId )
end

The problem is, that, when I want to build a DRL with the query I've got 
an error:

org.drools.rule.InvalidRulePackage: Not possible to directly access the 
property 'productId' of declaration '$p' since it is not a pattern : 
[Rule name=Query_1, agendaGroup=MAIN, salience=0, no-loop=false]
Unable to create restriction '[QualifiedIndentifierRestr: == 
$p.productId ]' for field 'productAID' in the rule 'Query_1' : [Rule 
name=Query_1, agendaGroup=MAIN, salience=0, no-loop=false]


The question is: why?
Of course, all types are imported, etc.

Moreover, when I modify the query as a following:

query "Query_1" (Product $p)
   $p1 : Product (  ) from $p
   $r : Relation( productAID == $p1.productId )
end

then everything works fine.

Is it a desirable behaviour?

I hope the description above is enough to understand the problem, but if 
anyone needed full Java source and DRLs, please, let me know.

Best regards,
-- 
Przemysław Różycki
AMG.net, A Bull Group Company
ul. Łąkowa 29
90-554 Łódź
www.amg.net.pl