[rules-users] Accessing maps (hashmaps) keys and values in rules

[Anstis, Michael (M.)]

By way of example (if you misunderstand how the rule engine should be
used):-
 
rule chkobj
when
    $o : MyClass( id == "1", name == "name" )
then
    //Do something else
    $o.doSomething();
end


  _____  

From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Edson Tirelli
Sent: 01 November 2007 15:48
To: Rules Users List
Subject: Re: [rules-users] Accessing maps (hashmaps) keys and values in
rules



   Shaz,

   We strongly advise you to move to 4.0.3, but this is not related to your
problem. 
   I think you are misunderstanding something. Why are you using the global
map to store your fact? Simply insert it into the working memory and it will
work fine. 

   []s
   Edson



2007/11/1, Shaz Tumulak <shauii at yahoo.com>: 


Hi,

I can't seem to make this syntax work in Drools 4.0.2. Pls. see my sample
code below.
________________________________________
class MyClass {
        String id;
        String name;

        MyClass(String id, String name){
                this.id = id;
                this.name = name;
        }
        :
        getter, setter methods 
        :
}

MyClass obj = new MyClass("1"", "name");

TreeMap<String, MyClass> mapOfObj = new TreeMap<String, MyClass>();
mapOfObj.put("keyOfObj", obj); 
________________________________________

DRL file
-------

global java.util.TreeMap mapOfObj;

rule chkobj
when
        obj : MyClass(mapOfObj["keyOfObj"].id == "1");
        eval(obj.getName() == "name");
________________________________________

I'm getting this error: org.drools.RuntimeDroolsException:
java.lang.NullPointerException
                            at 
org.drools.rule.EvalCondition.isAllowed(EvalCondition.java:76)

Is my syntax correct and has someone used this in 4.0.2 or should I move on
to Drools 4.0.3? Thanks in advance.

Regards,

shaz


Edson Tirelli-3 wrote:
>
>    Denis,
>
>    If you are using latest build from trunk (I'm not sure it already works
> in MR3), you can use a simplified MVEL syntax:
>
> when 
>     Person( address["business"].phone == "99999999" )
> then
>     ...
> end
>
>    Although, the above will be converted into an inline-eval. Not as bad
> as 
> a top level eval, but still more costly then using regular fields.
>
>    []s
>    Edson
>
> 2007/7/19, Ryan, Dennis (Dennis) <dennisryan at avaya.com
<mailto:dennisryan at avaya.com> >:
>>
>>  We are using Maps (HashMaps) in our rules and the only way we have found
>> to access keys and values in the Map in the "when" clauses is thru use on
>> eval() which I know is a big no-no by rules purists. Is there a better 
>> way,
>> maybe some shorthand I'm not familiar with to deal with Maps in the when
>> clause?
>>
>>
>>
>> Thanks,
>>
>> Dennis
>> 
>> _______________________________________________
>> 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
> 
>
shauii at yahoo.com
--
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-- 
  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 

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