[rules-users] Getting hold of the Evaluator Registry

Asif Iqbal Asif.Iqbal at infor.com
Wed Jul 15 10:09:55 EDT 2009 

Thanks..

________________________________
From: rules-users-bounces at lists.jboss.org [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Edson Tirelli
Sent: 15 July 2009 14:57
To: Rules Users List
Subject: Re: [rules-users] Getting hold of the Evaluator Registry


   Yes, you are in the right track, and I understand this is a bit confusing at first. One more reason for people to go to the October Rules Fest 2009 where I will give a presentation on all the ways to extend the engine to solve specific problems. It will be interesting I hope (last year was awesome) and even Charles Forgy will be there doing a presentation on Parallel Rete. :)

    Meanwhile I will write a tutorial on this, but just to help you there, your approach is correct, except that you don't need to setup the option for each operator. It works like this:

* One EvaluatorDefinition class implements support to one or more evaluators, defined by the method public String[] getEvaluatorIds().

* All you need to do, then, is wire you class once and the engine will pick-up all the IDs supported by that class. When you have your class wired, you give it a unique string identifier, so that if you ever need to replace it, or remove it, you will use that id. Sometimes we use the operator as the ID, but usually it is something that reminds you of the kind of evaluators that class define. For instance, drools registers the ComparableEvaluatorsDefinition in this way:

drools.evaluator.comparable = org.drools.base.evaluators.ComparableEvaluatorsDefinition

  So in this case, "comparable" is the identifier. Finally, from my previous e-mail you will see that the reason that the eclipse IDE is still giving you errors is that you are using the API to configure the evaluators. Just move the configuration to the configuration file and the IDE will pick it up.

   []s
   Edson


2009/7/15 Asif Iqbal <Asif.Iqbal at infor.com<mailto:Asif.Iqbal at infor.com>>

Edson,



What I have done so far is created a CustomComparableEvaluatorsDefinition, which is exactly the same as the default ComparableEvaluatorsDefinition apart form having support for strings, which I have done by creating StringGreaterOrEqualEvaluators and added that in my custom class, using the addEvaluatorFunction :-



            addEvaluator( ValueType.SHORT_TYPE,         Operator.GREATER,             ShortGreaterEvaluator.INSTANCE );

            addEvaluator( ValueType.SHORT_TYPE,         Operator.GREATER_OR_EQUAL,    ShortGreaterOrEqualEvaluator.INSTANCE );

            addEvaluator( ValueType.PSHORT_TYPE,        Operator.LESS,                ShortLessEvaluator.INSTANCE );

            addEvaluator( ValueType.PSHORT_TYPE,        Operator.LESS_OR_EQUAL,       ShortLessOrEqualEvaluator.INSTANCE );

            addEvaluator( ValueType.PSHORT_TYPE,        Operator.GREATER,             ShortGreaterEvaluator.INSTANCE );

            addEvaluator( ValueType.PSHORT_TYPE,        Operator.GREATER_OR_EQUAL,    ShortGreaterOrEqualEvaluator.INSTANCE );

            //Custom additions

            addEvaluator( ValueType.STRING_TYPE,        Operator.LESS,                StringLessEvaluator.INSTANCE );

            addEvaluator( ValueType.STRING_TYPE,        Operator.LESS_OR_EQUAL,       StringLessOrEqualEvaluator.INSTANCE );

            addEvaluator( ValueType.STRING_TYPE,        Operator.GREATER,             StringGreaterEvaluator.INSTANCE );

            addEvaluator( ValueType.STRING_TYPE,        Operator.GREATER_OR_EQUAL,    StringGreaterOrEqualEvaluator.INSTANCE );



Now Im am trying to wire it, with the following..



                        CustomComparableEvaluatorsDefinition MyCustomComparable custom = new CustomComparableEvaluatorsDefinition();

                        KnowledgeBuilderConfiguration config = KnowledgeBuilderFactory.newKnowledgeBuilderConfiguration();

                        EvaluatorOption option = EvaluatorOption.get(Operator.LESS.toString(), custom);

                        EvaluatorOption option2 = EvaluatorOption.get(Operator.LESS_OR_EQUAL.toString(), custom);

                        EvaluatorOption option3 = EvaluatorOption.get(Operator.GREATER.toString(), custom);

                        EvaluatorOption option4 = EvaluatorOption.get(Operator.GREATER_OR_EQUAL.toString(), custom);



                        config.setOption(option);

                        config.setOption(option2);

                        config.setOption(option3);

                        config.setOption(option4);



Firstly is this the correct approach?....



The problem im having is that in my drl files still flag errors, when I do "test" > "test2" , am I missing something?



Regards



________________________________

From: rules-users-bounces at lists.jboss.org<mailto:rules-users-bounces at lists.jboss.org> [mailto:rules-users-bounces at lists.jboss.org<mailto:rules-users-bounces at lists.jboss.org>] On Behalf Of Asif Iqbal
Sent: 15 July 2009 08:20
To: Rules Users List
Subject: RE: [rules-users] Getting hold of the Evaluator Registry



Edson,



Thanks for your replies they have really helped.



1)       I am still not sure about creating a new operator, since the '>=' operator already exists it just does not cater for strings, which I want to add. So would creating a new operator cause the existing one to be overrriden when added to the registry?



2)       Having looked at the examples and tests you emailed, I am still unsure how to actually wire in the changes, say for example I have replaced the existing '>=' evaluator or created a new evaluator so that '>='  now handles strings. When writing rules will the engine pick this up?.. or do I need to create a new jar by building?.. or do I need to update a configuration file?... im just not sure...



3)       Wouldn't the following also add the evaluator definition by replacing the existing one..



                  PackageBuilderConfiguration pkgb = new PackageBuilderConfiguration();

                  pkgb.getEvaluatorRegistry().addEvaluatorDefinition(new ComparableEvaluatorsDefinition());

                  PackageBuilder builder = new PackageBuilder(pkgb);



                  builder.addPackageFromDrl(source);

                  Package pkg = builder.getPackage();

                  // Add the package to a rulebase (deploy the rule package).

                  rules = RuleBaseFactory.newRuleBase();

                  rules.addPackage(pkg);



Thanks for your help...



________________________________

From: rules-users-bounces at lists.jboss.org<mailto:rules-users-bounces at lists.jboss.org> [mailto:rules-users-bounces at lists.jboss.org<mailto:rules-users-bounces at lists.jboss.org>] On Behalf Of Edson Tirelli
Sent: 14 July 2009 23:05
To: Rules Users List
Subject: Re: [rules-users] Getting hold of the Evaluator Registry



   I am working in one example of drools features where I implement a custom evaluator here:

http://anonsvn.jboss.org/repos/labs/labs/jbossrules/contrib/lotrc/src/main/java/org/drools/examples/lotrc/evaluators/IsAdjacentToEvaluatorDefinition.java

   I use the configuration file instead of API in the example:

http://anonsvn.jboss.org/repos/labs/labs/jbossrules/contrib/lotrc/src/main/resources/META-INF/drools.packagebuilder.conf

   []s
   Edson

2009/7/14 Edson Tirelli <tirelli at post.com<mailto:tirelli at post.com>>

   Asif,

   My recommendation is create a new operator for you instead of overriding existing ones. Although if you really want to replace the existing ones, setting the property or calling the API to register a new operator will override the default.

   See:

http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-compiler/src/test/java/org/drools/builder/KnowledgeBuilderConfigurationTest.java

   Test method:

testEvaluatorConfiguration()

   []s
   Edson

2009/7/14 Asif Iqbal <Asif.Iqbal at infor.com<mailto:Asif.Iqbal at infor.com>>

Hi,



What I need to do is modify one of the evaluator classes specifically '<=', so that it can handle strings. Now I know I need to create a class similar to ComparableEvaluatorDefinition. But what I want to do is replace the existing one in the evaluator registry with my implementation which will include the additional String capability.



>From my understanding that should be all that is required. Unless im missing something... now all I need to know is how do I get hold of the evaluator registry?



Cheers



I



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--
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com<http://www.jboss.com>



--
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com<http://www.jboss.com>

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--
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com<http://www.jboss.com>
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