[rules-users] Adding a custom operator to drools?

[Edson Tirelli]

   Hi Michael,

   All good suggestions. I will create a JIRA with them and apply as soon as
possible.

   Regarding the tutorial, it would be great. We can add it to the Drools
documentation with proper credits to you!

   Thanks,
       Edson

2008/9/17 Michael Zimmermann <list at incunabulum.de>

> Hi Edson,
>
> I think I got it working :-)
>
> Edson Tirelli wrote:
> > For an example, look at the file SetEvaluatorsDefinition and look at
> > the BaseMemberOf inner class. So, all the logic is in there, but we
> > still used subclasses just to set the constructor attributes and
> > override the toString() method, but you could still implement
> > everything in a single class I guess.
>
> Yes, this approach makes sense as long as you don't need to use the
> different VariableContextEntry subclasses for handling double, char etc.
> Yet, this can be handled, too.
>
> toString():
> You can avoid subclassing from your BaseMyEvaluatorClass to override
> toString() by using a string method like:
>
> public String toString() {
>  return getValueType().getName() + " " +
>         getOperator().getOperatorString();
> }
>
> Regarding the evaluator API:
> If you only need one evaluator class (subclassed from BaseEvaluator),
> personally I don't like the > 10 static calls to
>    addEvaluator(type, operator, myEvaluatorInstance)
> in the EvaluatorDefinition class.
>
> So, how about adding the method addDefaultEvaluator(operator,
> evaluatorClass) to EvaluatorCache, see attachment?
> This would allow you to register a evaluator as default and only overide
> the special cases...
>
>
> PS: If you are interested I will write some small tutorial about custom
> evaluators / operators in drools trunk. This might take a week or two,
> though. Any preferences regarding the format?
>
> Thanks for the help....
>
> cu, Michael
>
>
> @SuppressWarnings("unchecked")
> public void addDefaultEvaluator(final Operator operator, Class
> evaluatorClass) {
> // define the constructor
> Class[] evaluatorParameters = new Class[2];
> evaluatorParameters[0] = ValueType.class;
> evaluatorParameters[1] = Operator.class;
>
> // get the constructor
>        try {
>        Constructor<BaseEvaluator> constructor;
>                constructor = evaluatorClass.getConstructor(
> evaluatorParameters );
>
>                // add feault operators
>        addEvaluator(ValueType.ARRAY_TYPE, operator,
> constructor.newInstance(ValueType.ARRAY_TYPE, operator));
>        addEvaluator(ValueType.BIG_DECIMAL_TYPE, operator,
> constructor.newInstance(ValueType.BIG_DECIMAL_TYPE, operator));
>        addEvaluator(ValueType.BIG_INTEGER_TYPE, operator,
> constructor.newInstance(ValueType.BIG_INTEGER_TYPE, operator));
>        addEvaluator(ValueType.BOOLEAN_TYPE, operator,
> constructor.newInstance(ValueType.BOOLEAN_TYPE, operator));
>        addEvaluator(ValueType.PBOOLEAN_TYPE, operator,
> constructor.newInstance(ValueType.PBOOLEAN_TYPE, operator));
>        addEvaluator(ValueType.BYTE_TYPE, operator,
> constructor.newInstance(ValueType.BYTE_TYPE, operator));
>        addEvaluator(ValueType.PBYTE_TYPE, operator,
> constructor.newInstance(ValueType.PBYTE_TYPE, operator));
>        addEvaluator(ValueType.CHAR_TYPE, operator,
> constructor.newInstance(ValueType.CHAR_TYPE, operator));
>        addEvaluator(ValueType.PCHAR_TYPE, operator,
> constructor.newInstance(ValueType.PCHAR_TYPE, operator));
>        addEvaluator(ValueType.DATE_TYPE, operator,
> constructor.newInstance(ValueType.DATE_TYPE, operator));
>        addEvaluator(ValueType.DOUBLE_TYPE, operator,
> constructor.newInstance(ValueType.DOUBLE_TYPE, operator));
>        addEvaluator(ValueType.PDOUBLE_TYPE, operator,
> constructor.newInstance(ValueType.PDOUBLE_TYPE, operator));
>        addEvaluator(ValueType.FLOAT_TYPE, operator,
> constructor.newInstance(ValueType.FLOAT_TYPE , operator));
>        addEvaluator(ValueType.PFLOAT_TYPE, operator,
> constructor.newInstance(ValueType.PFLOAT_TYPE, operator));
>        addEvaluator(ValueType.INTEGER_TYPE, operator,
> constructor.newInstance(ValueType.INTEGER_TYPE, operator));
>        addEvaluator(ValueType.PINTEGER_TYPE, operator,
> constructor.newInstance(ValueType.PINTEGER_TYPE, operator));
>        addEvaluator(ValueType.LONG_TYPE, operator,
> constructor.newInstance(ValueType.LONG_TYPE, operator));
>        addEvaluator(ValueType.PLONG_TYPE, operator,
> constructor.newInstance(ValueType.PLONG_TYPE, operator));
>        addEvaluator(ValueType.OBJECT_TYPE, operator,
> constructor.newInstance(ValueType.OBJECT_TYPE, operator));
>        addEvaluator(ValueType.SHORT_TYPE, operator,
> constructor.newInstance(ValueType.SHORT_TYPE, operator));
>        addEvaluator(ValueType.PSHORT_TYPE, operator,
> constructor.newInstance(ValueType.PSHORT_TYPE, operator));
>        addEvaluator(ValueType.STRING_TYPE, operator,
> constructor.newInstance(ValueType.STRING_TYPE, operator));
>        } catch (SecurityException e) {
>                // TODO Auto-generated catch block
>                e.printStackTrace();
>        } catch (NoSuchMethodException e) {
>                // TODO Auto-generated catch block
>                e.printStackTrace();
>        } catch (IllegalArgumentException e) {
>                // TODO Auto-generated catch block
>                e.printStackTrace();
>        } catch (InstantiationException e) {
>                // TODO Auto-generated catch block
>                e.printStackTrace();
>        } catch (IllegalAccessException e) {
>                // TODO Auto-generated catch block
>                e.printStackTrace();
>        } catch (InvocationTargetException e) {
>                // TODO Auto-generated catch block
>                e.printStackTrace();
>        }
> }
>
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>


-- 
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
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