Esteban, I have created a ticket for this with
an explanation of the weird behavior.

https://issues.jboss.org/browse/DROOLS-414

The problem is in QueryElementBuilder line#343.
It's an easy fix but I don't have time for it right now,
could someone look into it?

Thanks
Davide

On 01/22/2014 06:00 PM, Esteban Aliverti wrote:

Good catch Davide. I can confirm that not using nested accessors the query works as expected.

Regards,

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Esteban Aliverti
- Blog @ http://ilesteban.wordpress.com

On Wed, Jan 22, 2014 at 6:57 PM, Davide Sottara <dsotty@gmail.com> wrote:

Indeed, the use case can be simplified further:

package org.drools.test.bc;

declare Parent
    attribute2 : String
end

declare Child
    parentId : String
end

query getChildWithName( String $parentId, Child $child )
    $child:= Child( parentId == $parentId )

end

rule "Insert Children"
when

then
    Parent p1 = new Parent( "a1" );
    Child c1p1 = new Child( "1" );

    insert( c1p1 );
    insert( p1 );

end

rule "Rule A"
when

    $p: Parent( $a2 : attribute2 )
    ?getChildWithName( $p.attribute2, $child;)
then
    System.out.println("FOUND: "+ $child + " >> " + $child.getParentId() + " == " + $p.getAttribute2() + " ??" );
end

It has nothing to do with nested objects, @PR or modifications.
It seems that the culprit is the chained property accessor.

Davide



On 01/22/2014 02:22 PM, Esteban Aliverti wrote:

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,

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Esteban Aliverti
- Blog @ http://ilesteban.wordpress.com

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