[rules-users] Rule does not fire after 'Modify/Update' of a fact - Drools 5.1.1 !
Hello all,
For some reason I have a rule that does not fire after a Modify/Update.
I have 2 facts - Product and Option. The relationship between them is that a
'Product' can have 0 - N 'Option'(s).
Based on that, I added a 'product' field to the 'Option' object. I'm
creating and inserting my facts
using the following code :
Product prod = new Product ("001","002", "A");
prod.setPrice(new BigDecimal("300.00"));
Option opt = new Option ("H1","",prod);
ksession.insert(prod);
ksession.insert(opt);
Now in my .DLR, I have the following rule :
rule "Set Options price"
salience 50
when
$prod : Product ( price != null )
$option : Option ( product == $prod )
then
System.out.println( "Getting Options " + $prod );
end
This gives me the correct output in the console :
Getting Options Product [category=001, grade=A, price=300.00, style=002]
The rule fired successfully.
I start running into problems when I try to update the 'price' field using a
rule, instead of through code.
So for example, if I have the following rule also defined in the same drl
file :
rule "Set price"
salience 500
when
$prod : Product ( category == "001", price == null )
then
$prod.setPrice ( new BigDecimal ( "300.00" ) );
update( $prod );
System.out.println( $prod );
end
And then change my code as follows (remove the setPrice call) :
Product prod = new Product ("001","002", "A");
Option opt = new Option ("H1","",prod);
ksession.insert(prod);
ksession.insert(opt);
I only get the following output :
Product [category=001, grade=A, price=300.00, style=002]
What am I missing here ? I thought the rule 'Set Price' should update the
product fact with
the new price and the rules would get re-evaluated. After the re-evaluation,
the LHS of 'Set Options Price' should now be true and it should have fired.
But it does not.
Am I mis-understanding something about activation here ? If I am, can
someone please help explain what the gap is and how to re-write the rules so
that I can achieve the above objective ?
Any help will be appreciated. I've spend several hours trying different
permutations and combinations and got no where.
Thanks
Gurvinder
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