RE: [drools-dev] About multiple predicate constraints in drl

[Yong Ming, Chen]

Thanks for your reply, Steven and Michael, your information really help me a lot in using Drools.   From: Michael Neale [mailto:[EMAIL PROTECTED] Sent: Wednesday, October 25, 2006 5:44 PM To: dev@drools.codehaus.org Subject: Re: [drools-dev] About multiple predicate constraints in drl   Yes, Steven is correct. In the next major version, we are planning on allowing more "free form" predicates as constraints, and the parser will convert then to the equivalent of eval() in most cases (so its sugar) - of course, using simple field constraints (at least one) will *always* help performance, as it allows the alpha node network to filter as much data as possible before it hits things like "eval" which are less efficient (ie if there is less data hitting the less efficient tests, then performance won't suffer). FYI, in future, please use the user list for usage questions. On 10/25/06, Steven Williams < [EMAIL PROTECTED]> wrote: No, you cannot use a declaration from the same condition in a predicate. I think you would need to split it out into an eval.   On 10/25/06, Yong Ming, Chen <[EMAIL PROTECTED]> wrote: Hi, all,   I'm using Drools 3.0.4 drl to test some simple rules, the drl I'm using is similar to below,   Import Applicant; rule "test_applicant_rule"       when             $applicant: Applicant ($age: age, $salary : salary ->(($salary>1000) && ($age>21) && ($salary > $age)) )       then             System.out.println("approve applicant"); end   where "Applicant" is a class has int attributes "age", and "salary"   public class Applicant {             private int age;             private int salary;   … }   The drl is deployed into Drools successfully, but when I invoke the rule engine by asserting "applicant" objects into working memory, Drools will throw runtime exceptions as below:   org.drools.RuntimeDroolsException : java.lang.NullPointerException       at org.drools.rule.PredicateConstraint.isAllowed( PredicateConstraint.java:94 )       at org.drools.common.BetaNodeBinder.isAllowed( BetaNodeBinder.java:63 )       at org.drools.reteoo.LeftInputAdapterNode.assertObject( LeftInputAdapterNode.java:138 )       at org.drools.reteoo.ObjectSource.propagateAssertObject( ObjectSource.java:119 )       at org.drools.reteoo.ObjectTypeNode.assertObject( ObjectTypeNode.java:158 )       at org.drools.reteoo.Rete.assertObject( Rete.java:120 )       at org.drools.reteoo.ReteooRuleBase.assertObject( ReteooRuleBase.java:180 )       at org.drools.reteoo.ReteooWorkingMemory.doAssertObject( ReteooWorkingMemory.java:69 )       at org.drools.common.AbstractWorkingMemory.assertObject( AbstractWorkingMemory.java:538 )       at org.drools.common.AbstractWorkingMemory.assertObject( AbstractWorkingMemory.java:394 )       at prototype.DRLTest.main( DRLTest.java:80 ) Caused by: java.lang.NullPointerException       at tmp.Rule_test_applicant_rule_0Predicate0Invoker.evaluate( Rule_test_applicant_rule_0Predicate0Invoker.java:13 )       at org.drools.rule.PredicateConstraint.isAllowed( PredicateConstraint.java:88 )   After looking into it, I found it's the predicate constraint in the condition drl is causing problem, $applicant: Applicant ($age: age, $salary : salary ->(($salary>1000) && ($age>21) && ($salary > $age)) ) As shown above, in salary's predicate constraint, age declaration is used, Could anyone help to answer me, am I using the drl in correct way? Or dose Drools support using multiple declarations in one predicate constraint?   Chen Yong Ming Software Engineer, Technology Development DID: 65 – 6887 7500 Fax: 65 – 6778 5277   CrimsonLogic Pte Ltd (Regn No: 198800784N) 31 Science Park Road, The Crimson, Singapore 117611 Main Line: +65 6887 7888 Fax: +65 6778 5277 Visit us at www.crimsonlogic.com Makes better sense ======================================================== NOTICE This eMail and any attachments are intended solely for the named addressee(s) only. It contains confidential and/or privileged information which should not be copied or disclosed without the consent of the CrimsonLogic group. If you are not the intended recipient or if you have received this eMail in error, you must not copy, distribute, disclose or take any action in reliance on it (or any part of its contents). 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