Hi there, you might see this as a follow up to a discussion named "Query by Example" a couple of days ago, see here: http://lists.jboss.org/pipermail/rules-users/2008-September/006520.html Question to the devs: Having looked through the code, adding support for a custom operator requires - changing the DRL.g - regenerating the DRLLexer and DRLParser classes from this grammar - changing the XyzEvaluator and related classes in org.drools.base.evaluators. If I skip MVEL, the BRMS and other places like decision tables for now, is this all to expand the DRL syntax? Or are any further steps required to connect the grammar with the "java logic"? Thanks! Michael _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

It depends if you are talking about Drools 4 or 5. You are right about Drools 4. Drools 5 has "quasi-pluggable" operators... hehehe :)

For more info, look at the EvaluatorDefinition interface in Drools 5 and its several implementations for examples.

BTW, most important thing that I forgot to mention: we obviously are interested in feedback and contributions on the feature, from simple ideas and suggestions to actual patches and improvements!

Drools 5 is not production ready yet, specially because we are still working in the new major features like CEP and processes, but the 4.x equivalent features all work.

Also, if your research project is not expected to be final in the next month or so, by the time you finish your project we will have Drools 5 final out.

BTW, can you talk about about the subject of your research?

It has an interface you can implement to add operators and the parser accepts a quote for custom operators. It is not yet the way I want it to be for Drools 5 final, but it works already. For more info, look at the EvaluatorDefinition interface in Drools 5 and its several implementations for examples.

Hi Edson, just spend some hours compiling the most recent drools version from svn trunk and migrating my application to this version. So far, most of the features work except - of one issue with BaseIntClassFieldReader, see JIRA ticket 1766. - and an incorrect import in SendIcal.java leading to a broken maven build proces, see JIRA ticket 1767. Edson Tirelli wrote: > It has an interface you can implement to add operators and the parser > accepts a quote for custom operators. It is not yet the way I want it to > be for Drools 5 final, but it works already. > > For more info, look at the EvaluatorDefinition interface in Drools 5 > and its several implementations for examples. Having looked at the EvaluatorDefinition the implementation of custom operators seem to be straightforward now. Nice Work! 1) One question though: In drools-core each subclass of BaseEvaluator calls the parent class as follows public MyEvaluator() super(ValueType.SOME_TYPE, Operator.MY_OPERATOR); with the operators created using the private (!) constructor Operator(id, negated) via some static variable in Operator.java. So, well, how do I hook up a custom operator to e. g. a drools package? There is a PackageBuilderConfiguration.addEvaluatorDefinition() method, yet currently the only way to define the operator symbol ("==" etc) is via a separate call to Operator.addOperatorToRegistry() first and using the return Operator instance to create my EvaluatorDefinition. Or do I get something wrong? 2) Also, I am wondering about the large number of nearly identical internal classes required for each operator.Is there a specific reason why such an operator has to be defined for each possible object type separately? Is this due to the way the InternalReadAccessor is called to map to the current datatype in an operator call? And why not just call cu, Michael PS: Some details about my project come once I find a bit of time to write them down coherently :-) _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

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(); } } _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users