Hi guys,
I was writing some rules using backward chaining and found
a strange behavior.
I managed to isolate the error in the test project I'm
attaching.
In the project I have 2 classes: Parent and Child
Parent:
* String id
* String attribute1
* String attribute2
* List<Child> children
Child:
* String parentId;
* String name;
* String value;
In the test I'm creating 1 Parent object with just 1 child
and then inserting the Parent object into a drools session:
Parent p1 = new Parent();
p1.setId("1");
p1.setAttribute1("a1");
p1.setAttribute2(null);
Child c1p1 = new Child();
c1p1.setName("n1");
c1p1.setParentId(p1.getId());
c1p1.setValue("v1.1");
p1.addChild(c1p1);
kSession.insert(p1);
kSession.fireAllRules();
So far so good.
The rules I have in my session are the following:
declare Parent
@propertyReactive
end
query getChildWithName(String $parentId, String $name,
Child $child)
$child:= Child(parentId == $parentId, name == $name)
end
rule "Insert Children"
when
$p: Parent() @watch(!*)
$c: Child() from $p.children
then
System.out.println("Inserting child "+$c);
insert($c);
end
rule "Rule A"
when
$p: Parent(attribute2 != null)
?getChildWithName($p.attribute2, "n1", $child;)
then
System.out.println("FOUND: "+$child+". The attribute
'parentId' of this object must have the value
'"+$p.getAttribute2()+"'. Does it? "+$child.getParentId()+"
== "+$p.getAttribute2()+" ??");
globalList.add($child);
end
rule "Copy Attribute1 into Attribute2"
when
$p: Parent(attribute1 != null, attribute2 == null)
then
modify($p){
setAttribute2($p.getAttribute1())
}
end
The important part here is 'Rule A' and 'Copy Attribute1
into Attribute2'. The latter copies the value of attribute1 to
attribute2 for any Parent object present in the session. (Note
that the parent I'm inserting has attribute2 = null). 'Rule A'
is then using a query to get a Child object that has a parent
with id = $p.attribute2 (where $p is a previously matched
Parent).
Given that I only have 1 Parent in my session and that its
id is '1' I don't expect 'Rule A' to be activated/executed.
When I modify parent.attribute2 in 'Copy Attribute1 into
Attribute2' I'm setting its value to 'a1'. 'Rule A' (via the
query) should then look for a Child with parentid = 'a1' and
It shouldn't find anything.
Funny thing is that 'Rule A' activates and fires. The child
object that is 'returned' by the query has a parentId of '1'
so I don't know how this behavior is possible. If you take a
look at the System.out output you will see that the activation
makes no sense at all.
Am I doing something wrong in my project? Is this a bug? Is
this the expected behavior?
Regards,