[rules-users] How to limit results from a collect statement
pentarious
cristiano.giuffrida at gmail.com
Wed Aug 22 12:49:56 EDT 2007
I hope you can help me find a solution. In the meantime I've tried your
workaround, adding an addOption() method with no success. When I use that
method in the rule I get the following exception (and I can't understand
why):
java.lang.ClassNotFoundException: org.test.ItemShadowProxy
org.test.Item is the full qualified name of the bean Item. Any idea?
Regards,
CG
Edson Tirelli-3 wrote:
>
> I think I know what is happening. The getOptions() method is returning
> the shadowed options collections, i.e., when you are adding the option,
> you
> are adding to the shadow instead of the real object.
>
> Now, I'm not sure how we should handle such thing, since we do need to
> shadow the options collection.
>
> Mark, any idea?
>
> A workaround is: create an addOption() method to the Item class to add
> options, instead of doing getOptions().add(). This way the shadow proxy
> will
> delegate the call to your real class, instead of adding it to the shadow.
>
> []s
> Edson
>
> 2007/8/22, pentarious <cristiano.giuffrida at gmail.com>:
>>
>>
>> Actually, before opening a JIRA I would like to show you my actual
>> code...
>> Here it is:
>>
>> rule "My Rule"
>> no-loop true
>> when
>> $list : ArrayList() from collect( Item( type == "MY TYPE" ) )
>> then
>> Item item = (Item) $list.get(0);
>> ItemOption option = new ItemOption( item, "MY OPTION" );
>> item.setType("MY NEW TYPE");
>> item.getOptions().add( option );
>> insert(option);
>> update(item);
>> end
>>
>> Basically we have some items (Item) and we need to take into
>> considerations
>> just items of type "MY TYPE", adding a new option "MY OPTION" to the list
>> of
>> the options of the first item in $list. Item is a bean with a field as
>> follows:
>> private Collection<ItemOption > options = new
>> ArrayList<ItemOption>();
>> I thought it was worth writing again before opening a JIRA, as I've
>> looked
>> further into the problem and I found out another interesting thing. As
>> you
>> may have noticed I put two lines in my code:
>> item.setType("MY NEW TYPE");
>> item.getOptions().add( option );
>> It's interesting to notice that the first line works as expected (i.e.
>> after
>> executing the rule the item has a new type called "MY NEW TYPE"), while
>> the
>> second line doesn't (i.e. after executing the rule the item doesn't have
>> a
>> new option in its option list). So, do you think I should definitively
>> open
>> a JIRA (I've never opened one before, can you give a link just in case?)
>> or
>> I'm just missing something and there is a trivial solution to this issue?
>>
>> Regards,
>>
>> CG
>>
>>
>> Edson Tirelli-3 wrote:
>> >
>> > Well, it must work. Can you open a JIRA with a self contained test
>> > case
>> > please? I will investigate.
>> >
>> > []s
>> > Edson
>> >
>> > 2007/8/22, pentarious <cristiano.giuffrida at gmail.com>:
>> >>
>> >>
>> >> I know. Actually I didn't put any update or insert statement in the
>> code
>> >> just
>> >> to make it simpler. The actual code looks like:
>> >> when
>> >> $itemList : ArrayList() from collect( Item( category == "VIDEO"
>> )
>> )
>> >> then
>> >> ItemDiscount disc = new ItemDiscount(10);
>> >> insert(disc);
>> >> $myFirstItem = (Item)$itemList.get(0);
>> >> $mySecondItem = (Item)$itemList.get(1);
>> >> $myFirstItem.addDiscount(disc);
>> >> $mySecondItem.addDiscount(disc);
>> >> update($myFirstItem);
>> >> update($mySecondItem);
>> >> Now, why this doesn't work at all? It does work if I write a rule for
>> >> each
>> >> item using in the when clause $item : Item from $itemList, but as I
>> said
>> >> I
>> >> need to write a list-oriented rule.
>> >>
>> >> Regards,
>> >>
>> >> CG
>> >>
>> >>
>> >> Edson Tirelli-3 wrote:
>> >> >
>> >> > If you want the "engine to see" your changes, in a way you affect
>> >> other
>> >> > rules, you must call update( object ) for the object you are
>> changing.
>> >> > Otherwise, the change will happen to the original object, but not to
>> >> the
>> >> > shadow proxy that the engine uses to ensure consistency.
>> >> >
>> >> > []s
>> >> > Edson
>> >> >
>> >> > 2007/8/22, pentarious <cristiano.giuffrida at gmail.com>:
>> >> >>
>> >> >>
>> >> >> Ok, I'm still working on that, I'll publish my solution asap. In
>> the
>> >> >> meantime
>> >> >> it turns out our requirements need something more than that. We
>> have
>> >> an
>> >> >> ordered list of beans (items) and we have to be able to modify a
>> >> specific
>> >> >> subset of the list (adding a discount). Now I tried to solve this
>> >> problem
>> >> >> by
>> >> >> working directly on the list of items. But I can't understand why
>> this
>> >> >> doesn't work:
>> >> >> when
>> >> >> $itemList : ArrayList() from collect( Item( category ==
>> "VIDEO"
>> )
>> >> )
>> >> >> then
>> >> >> ItemDiscount disc = new ItemDiscount(10);
>> >> >> $myFirstItem = (Item)$itemList.get(0);
>> >> >> $mySecondItem = (Item)$itemList.get(1);
>> >> >> $myFirstItem.addDiscount(disc);
>> >> >> $mySecondItem.addDiscount(disc);
>> >> >>
>> >> >> After executing this rule it's like nothing happened! I mean no
>> >> discount
>> >> >> has
>> >> >> been added to the two items! The problem seems to be related to
>> >> >> extracting
>> >> >> items from the list. Apparently, every time we get an item from the
>> >> list,
>> >> >> it
>> >> >> looses its link with the original item (I don't know if it's a copy
>> of
>> >> >> the
>> >> >> original item or whatever), so that every update doesn't affect the
>> >> >> original
>> >> >> item any more. But of course that's what we're interested in! We
>> want
>> >> to
>> >> >> modify original items in the rule session. Am I missing something?
>> Or
>> >> Is
>> >> >> it
>> >> >> a bug?
>> >> >>
>> >> >> Regards,
>> >> >>
>> >> >> CG
>> >> >>
>> >> >>
>> >> >>
>> >> >> Edson Tirelli-3 wrote:
>> >> >> >
>> >> >> > Please, share with us! Send to the list!
>> >> >> >
>> >> >> > Edson
>> >> >> >
>> >> >> > 2007/8/21, pentarious <cristiano.giuffrida at gmail.com>:
>> >> >> >>
>> >> >> >>
>> >> >> >> I found an interesting implementation to do that. If anyone is
>> >> >> interested
>> >> >> >> I
>> >> >> >> could share my solution.
>> >> >> >>
>> >> >> >> Regards,
>> >> >> >>
>> >> >> >> CG
>> >> >> >>
>> >> >> >>
>> >> >> >> Mark Proctor wrote:
>> >> >> >> >
>> >> >> >> > There is no supported way to do this. You could use an
>> >> inline-eval
>> >> >> >> > against a global, but that is very clunkey. However it does
>> seem
>> >> >> like
>> >> >> a
>> >> >> >> > good feature idea for a future release, open a jira and I'll
>> look
>> >> >> into
>> >> >> >> > getting it included.
>> >> >> >> >
>> >> >> >> > Mark
>> >> >> >> > pentarious wrote:
>> >> >> >> >> Does anyone know a method to limit the number of results from
>> a
>> >> >> >> collect
>> >> >> >> >> statement? I was just wondering how to do something like
>> this:
>> >> >> >> >> $myList : List() from collect( MyObject(myField ==
>> "something")
>> >> )
>> >> >> >> limit
>> >> >> >> 3
>> >> >> >> >> //it should put in $myList just the first 3 objects retrieved
>> >> >> >> >> I'm quite sure there is nothing in Drools which can natively
>> >> >> support
>> >> >> >> >> something like that. So, how to do that, if needed? I tried
>> >> this,
>> >> >> but
>> >> >> >> it
>> >> >> >> >> seems not to be working (I can't understand why, though):
>> >> >> >> >> $myList : List() from collect( MyObject(myField ==
>> "something")
>> >> )
>> >> >> >> >> $myObject : MyObject() from $myList
>> >> >> >> >> eval( $myList.indexOf($myObject) < 3 )
>> >> >> >> >> Indeed, it doesn't work because the link beetween $myList and
>> >> >> >> $myObject
>> >> >> >> >> seems to be released during any execution of the rule (In
>> fact
>> >> >> >> >> $myList.contains($myObject) returns false! Again, I can't
>> >> >> understand
>> >> >> >> >> why...)
>> >> >> >> >>
>> >> >> >> >> Any advice would be really appreciated!
>> >> >> >> >>
>> >> >> >> >> Regards,
>> >> >> >> >>
>> >> >> >> >> CG
>> >> >> >> >>
>> >> >> >> >
>> >> >> >> > _______________________________________________
>> >> >> >> > rules-users mailing list
>> >> >> >> > rules-users at lists.jboss.org
>> >> >> >> > https://lists.jboss.org/mailman/listinfo/rules-users
>> >> >> >> >
>> >> >> >> >
>> >> >> >>
>> >> >> >> --
>> >> >> >> View this message in context:
>> >> >> >>
>> >> >>
>> >>
>> http://www.nabble.com/How-to-limit-results-from-a-collect-statement-tf4235669.html#a12249025
>> >> >> >> Sent from the drools - user mailing list archive at Nabble.com.
>> >> >> >>
>> >> >> >> _______________________________________________
>> >> >> >> rules-users mailing list
>> >> >> >> rules-users at lists.jboss.org
>> >> >> >> https://lists.jboss.org/mailman/listinfo/rules-users
>> >> >> >>
>> >> >> >
>> >> >> >
>> >> >> >
>> >> >> > --
>> >> >> > Edson Tirelli
>> >> >> > Software Engineer - JBoss Rules Core Developer
>> >> >> > Office: +55 11 3529-6000
>> >> >> > Mobile: +55 11 9287-5646
>> >> >> > JBoss, a division of Red Hat @ www.jboss.com
>> >> >> >
>> >> >> > _______________________________________________
>> >> >> > rules-users mailing list
>> >> >> > rules-users at lists.jboss.org
>> >> >> > https://lists.jboss.org/mailman/listinfo/rules-users
>> >> >> >
>> >> >> >
>> >> >>
>> >> >> --
>> >> >> View this message in context:
>> >> >>
>> >>
>> http://www.nabble.com/How-to-limit-results-from-a-collect-statement-tf4235669.html#a12270505
>> >> >> Sent from the drools - user mailing list archive at Nabble.com.
>> >> >>
>> >> >> _______________________________________________
>> >> >> rules-users mailing list
>> >> >> rules-users at lists.jboss.org
>> >> >> https://lists.jboss.org/mailman/listinfo/rules-users
>> >> >>
>> >> >
>> >> >
>> >> >
>> >> > --
>> >> > Edson Tirelli
>> >> > Software Engineer - JBoss Rules Core Developer
>> >> > Office: +55 11 3529-6000
>> >> > Mobile: +55 11 9287-5646
>> >> > JBoss, a division of Red Hat @ www.jboss.com
>> >> >
>> >> > _______________________________________________
>> >> > rules-users mailing list
>> >> > rules-users at lists.jboss.org
>> >> > https://lists.jboss.org/mailman/listinfo/rules-users
>> >> >
>> >> >
>> >>
>> >> --
>> >> View this message in context:
>> >>
>> http://www.nabble.com/How-to-limit-results-from-a-collect-statement-tf4235669.html#a12272536
>> >> Sent from the drools - user mailing list archive at Nabble.com.
>> >>
>> >> _______________________________________________
>> >> rules-users mailing list
>> >> rules-users at lists.jboss.org
>> >> https://lists.jboss.org/mailman/listinfo/rules-users
>> >>
>> >
>> >
>> >
>> > --
>> > Edson Tirelli
>> > Software Engineer - JBoss Rules Core Developer
>> > Office: +55 11 3529-6000
>> > Mobile: +55 11 9287-5646
>> > JBoss, a division of Red Hat @ www.jboss.com
>> >
>> > _______________________________________________
>> > rules-users mailing list
>> > rules-users at lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/rules-users
>> >
>> >
>>
>> --
>> View this message in context:
>> http://www.nabble.com/How-to-limit-results-from-a-collect-statement-tf4235669.html#a12274411
>> Sent from the drools - user mailing list archive at Nabble.com.
>>
>> _______________________________________________
>> rules-users mailing list
>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>
>
>
> --
> Edson Tirelli
> Software Engineer - JBoss Rules Core Developer
> Office: +55 11 3529-6000
> Mobile: +55 11 9287-5646
> JBoss, a division of Red Hat @ www.jboss.com
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
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