[rules-users] How to check if a property IS null ?

[Wolfgang Laun]

Using a Java condition like "this == null" is a slip of the keyboard.
-W



On 15/08/2012, Hendy Irawan <hendy at soluvas.com> wrote:
> Thank you.
>
> Here's a very simple use case : https://github.com/ceefour/droolsnull
>
> Running this on Drools 5.4.0 will output:
>
> 00:29:34.122 [main] INFO  c.h.droolsnull.BookingService - getNullQty()
> called!
> 00:29:34.125 [main] INFO  c.h.droolsnull.BookingService - getFilledQty()
> called!
> 00:29:34.139 [main] INFO  c.hendyirawan.droolsnull.DroolsNull - Notify has
> filled sentTime: Thu Aug 16 00:29:34 WIT 2012
> 00:29:34.139 [main] INFO  c.hendyirawan.droolsnull.DroolsNull - Notify has
> NULL sentTime
> 00:29:34.140 [main] INFO  c.hendyirawan.droolsnull.DroolsNull - You've got
> a
> filled booking with qty 5.0
> 00:29:34.140 [main] INFO  c.hendyirawan.droolsnull.DroolsNull - You've got
> a
> NULL booking
> 00:29:34.140 [main] INFO  c.hendyirawan.droolsnull.DroolsNull -
> BookingService can return filled qty: 10.0
>
> Expected is one more:
>
> BookingService can return NULL qty
>
> BookingService.getNullQty() is called by the Drools rule but then ignored.
> How to capture this?
>
> The rules :
>
> package com.hendyirawan.droolsnull
> dialect "mvel"
>
> import org.slf4j.*;
>
> import com.hendyirawan.droolsnull.*;
>
> global Logger log;
> global BookingService bookingService;
>
> rule "Booking data with not null qty exists"
> 	when
> 		$booking      : Booking( $qty : qty != null )
> 	then
> 		log.info("You've got a filled booking with qty {}", {$qty});
> end
>
> rule "Booking data with null qty exists"
> 	when
> 		$booking      : Booking( qty == null )
> 	then
> 		log.info("You've got a NULL booking");
> end
>
> rule "BookingService can return null qty"
> 	when
> 		Double( this == null ) from bookingService.getNullQty()
> 	then
> 		log.info("BookingService can return NULL qty");
> end
>
> rule "BookingService can return filled qty"
> 	when
> 		$qty      : Double() from bookingService.getFilledQty()
> 	then
> 		log.info("BookingService can return filled qty: {}", {$qty});
> end
>
> rule "Notify has null sentTime"
> 	when
> 		$notify		: Notify( sentTime == null )
> 	then
> 		log.info("Notify has NULL sentTime");
> end
>
> rule "Notify has filled sentTime"
> 	when
> 		$notify		: Notify( $sentTime : sentTime != null )
> 	then
> 		log.info("Notify has filled sentTime: {}", {$sentTime});
> end
>
> The rule that isn't working :
>
> rule "BookingService can return null qty"
> 	when
> 		Double( this == null ) from bookingService.getNullQty()
> 	then
> 		log.info("BookingService can return NULL qty");
> end
>
> Thank you.
>
> Hendy
>
>
> (I also once had a criteria like " $notify		: Notify( sentTime == null ) "
> not working but can't reproduce it again yet. if I can find it I'll post
> again)
>
>
>
> --
> View this message in context:
> http://drools.46999.n3.nabble.com/How-to-check-if-a-property-IS-null-tp4019014p4019150.html
> Sent from the Drools: User forum mailing list archive at Nabble.com.
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