[rules-users] Question about Drools accessing a global HashMap and comparing it to an object value

[Greg Barton]

You really shouldn't be matching an entire collection of objects like that.

Think of each rule as capturing one "example" of an object in a given state, and doing something when that object is found.  So think of your first rule like this:

rule "Check for null State"
    when
        obj : MyObj(state == null || state == "") 
    then
        obj.addError("State must have a value");
end

Where all MyObj instances are inserted into working memory.

If you also insert all entries in the state2CodeMap into working memory, that rule becomes equally simple.  Let's say a State2Code object has String state and ArrayList<String>> codes properties, then the rule would look like this:

rule "Check for valid code"
    when
        obj : MyObj(objState : state, objCode : code)
        codes : State2Code(state == objState, objCode not memberOf codes)
    then
        obj.addError("Code is not valid for the State");
end

Make sense?

--- On Tue, 1/25/11, mviens <mike at viens.com> wrote:

> From: mviens <mike at viens.com>
> Subject: [rules-users] Question about Drools accessing a global HashMap and comparing it to an object value
> To: rules-users at lists.jboss.org
> Date: Tuesday, January 25, 2011, 3:37 PM
> 
> MyObj is a Java object that contains:
> 
>     String state;
>     String code;
>     public void addError(String message);
> 
> myObjList is an ArrayList<MyObj> containing from 2 to
> 20,000 objects
> 
> state2CodeMap is a HashMap<String,
> ArrayList<String>> containing an entry
> for each US state. The associated ArrayList contains a
> minimum of 1 entry,
> up to 200 entries.
> 
> I need to create a rule that checks all of the MyObj
> objects in myObjList,
> gets the appropriate ArrayList from state2CodeMap based on
> myObj.state and
> then if myObj.code not memberOf $codeList, run the "then"
> portion of the
> rule.
> 
> I have created about 60 fairly simple rules, that are
> working just fine, but
> this one is a little too complex for me to userstand how to
> write it in
> Drools. Looking at this page (
> http://blog.athico.com/2007/06/chained-from-accumulate-collect.html
> http://blog.athico.com/2007/06/chained-from-accumulate-collect.html
> ), I can
> see that nested "from" seems to be supported, but the page
> seems to be for
> Drools 4. Plus, I have had to teach myself Drools in the
> past week. I could
> really use some help with this. Any assistance is greatly
> appreciated!
> 
> Mike V.
> 
>     global List myObjList;
>     global HashMap state2CodeMap;
> 
>     # this rule is working just fine!
>     rule "Check for null State"
>         when
>             $objs :
> ArrayList() from collect(MyObj(state == null || state ==
> "") from myObjList)
>         then
>             for (MyObj myObj
> : (ArrayList<MyObj>)$objs)
>             {
>                
> myObj.addError("State must have a value");
>             }
>     end
> 
>     # I really have no idea how to write this
> rule
>     rule "Check for valid code"
>         when
>             $objs :
> ArrayList() from collect(MyObj())
>         then
>             for (MyObj myObj
> : (ArrayList<MyObj>)$objs)
>             {
>                
> myObj.addError("Code is not valid for the State");
>             }
>     end
> 
> -- 
> View this message in context: http://drools-java-rules-engine.46999.n3.nabble.com/Question-about-Drools-accessing-a-global-HashMap-and-comparing-it-to-an-object-value-tp2334346p2334346.html
> Sent from the Drools - User mailing list archive at
> Nabble.com.
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