[rules-users] Accessing maps (hashmaps) keys and values in rules
Anstis, Michael (M.)
manstis1 at ford.com
Fri Nov 2 05:20:38 EDT 2007
IMHO you should still think about putting the Map values into working
memory.
This would both simplify your rules and make their execution faster (eval
cannot be indexed, if I remember correctly).
You might need to adapt your data model representation into one that is more
efficient for use in a RETE network.
Can you explain your use case to help understand? Unless you have very good
reason to keep the facts in the Map your life will be more difficult than it
need be.
An "eval" returns a boolean indiciating whether the "pattern" matched and
therefore, whilst you can reference other bound LHS facts, you cannot bind
other objects to variables.
Thanks,
Mike
_____
From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of shaz
Sent: 02 November 2007 02:32
To: Rules Users List
Subject: Re: [rules-users] Accessing maps (hashmaps) keys and values in
rules
Hi,
I am placing objects in the Hashmap that were retrieved from the database.
There are currently a hundred objects that I'm storing in the HashMap. I
just made a simple example earlier :) . What works for me now is putting the
getting of the values in the eval(). However, I don't know how to assign the
values that I've taken from the Map.
eval( ( (MyClass)mapOfObj.get("keyOfObj")).getId() > 30);
How do I assign (MyClass)mapOfObj.get("keyOfObj") to a variable?
tnx,
shaz
----- Original Message ----
From: "Anstis, Michael (M.)" <manstis1 at ford.com>
To: Rules Users List <rules-users at lists.jboss.org>
Sent: Friday, November 2, 2007 12:17:51 AM
Subject: RE: [rules-users] Accessing maps (hashmaps) keys and values in
rules
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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Software Engineer - JBoss Rules Core Developer
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