[rules-users] ClassCastException

[Christoph Kramer]

Hi Shannon,
yes all eventtypes inherit from a base class, but the superclass doesn't 
include all the attributes I want to acces in the rules. Unfortunately I 
can't modify the classes since they're part of a  library that i'm using.
Here is my intention:
I get a bunch of different events and have to extract some data.
Every event has a field with EPC's to which all the rest of the data 
belongs. I want to extract all the single EPC's with its related data.
With pure Java the solution would be somethin like that:

void handleObjectEvent(ObjectEventType p_objEvent){
    List<EPC> epcs = p_objEvent.getEPC();
    if(epc!=null){
       for(EPC e : epcs){
            if(p_objEvent.getBizLocation() !=null){
                doSomething(e, p_objEvent.getBizLocation());
            }
            
            if(p_objEvent.getBizStep() !=null){
                doSomething(e, p_objEvent.getBizStep());
            }

            if(p_objEvent.getDisposition() !=null){
                doSomething(e, p_objEvent.getDisposition());
            }

           ...
           ...
       }
    }
}

For the other types of Events there would similar functions. Since there 
are a lot of if-statements in the functions I thougt that it would be 
nice to use rule engine instead.

Greetings,
Christoph


Shannon Lal wrote:
> Christoph,
> I am not sure that this is a rules problem as it seems to be more of a 
> Java problem.  Do you Event types all inherit from a base class?  
> Could you not just check to see on the base class is present?  Also, 
> you might want to add in SMALL example of what you are trying to do in 
> pure Java code (outside of Rules) as it might be easy to translate.
>
> Shannon
>
> On Thu, May 14, 2009 at 6:35 AM, Christoph Kramer <amrod at gmx.de 
> <mailto:amrod at gmx.de>> wrote:
>
>     Hi all,
>     i've some problems with a ClassCastException when using the
>     "or"-conditional element.
>     I have different Java-Beans which all have some string-values. Now
>     I want to create one rule which is able to handle every type of my
>     classes because it would be a lot of work to create one rule for
>     every class.
>     Depending on the type of beans in the working memory the programm
>     is crashing with an ClassCastException.
>
>     Here is a snippet of my drl-file with the "crashing-rule":
>
>     rule "BizLocation"
>       when
>           $epc : EPC()
>           QuantityEventType(epcClass == $epc.value ,$bizLoc:
>     bizLocation !=null ) or AggregationEventType(childEPCs.epc
>     contains $epc, $bizLoc : bizLocation != null) or
>     ObjectEventType(epcList.epc  contains $epc, $bizLoc : bizLocation
>     != null)
>       then
>           System.out.println("BizLocation: " +$bizLoc.getId());
>     end
>
>
>     There are some EPC's in the working memory and some Events (which
>     might be of type QuantityEventType, AggregationEventType or
>     ObjectEventType). When there are only ObjectEventType in the
>     working memory, everything works fine, but wenn there is an
>     QuantityEventType this rule crashes with
>     "org.fosstrak.epcis.model.QuantityEventType cannot be cast to
>     org.fosstrak.epcis.model.ObjectEventType".
>     I've lot of other, similar rules some of them crashing, others don't.
>
>
>     Can anyone give me a hint where is the error?
>
>     Thanks,
>     Christoph
>
>     PS: Sorry for the bad english :(
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