CODEWITHSUNDEEP
javaeclipsedrools
Srik
Srik

Reputation: 2381

functions library in drools

I have below two files in the same folder.RuleFile.drl is the rules library and Sample.drl is the functions library. I am getting error mentioned below when I try to execute the rules.

I am not sure what am I missing and how to resolve this error. Any help is greatly appreciated.

File: RuleFile.drl

package com.sample
rule "A stand alone rule"
    when
        //conditions
    then
        myFunction(5);
end

File: Sample.drl

package com.sample
function int myFunction(int val){
    return val;
}

I am getting the below error message in the eclipse and also when I run the code.

The method myFunction(int) is undefined for the type Rule_A_stand_alone_rule_3e142aa079ee4a37b0fb21f9e9d9c0da

Java Code:

public class DroolsTest {
    private static final String RULES_CHANGE_SET = "RuleConfig.xml";
    public static final void main(String[] args) {
        try {
            // load up the knowledge base
            KnowledgeBase kbase = readKnowledgeBase();
            StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
            KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test");
        } catch (Throwable t) {
            t.printStackTrace();
        }
    }

    private static KnowledgeBase readKnowledgeBase() throws Exception {
        KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
        kbuilder.add(ResourceFactory.newClassPathResource(RULES_CHANGE_SET), ResourceType.CHANGE_SET);
        KnowledgeBuilderErrors errors = kbuilder.getErrors();
        if (errors.size() > 0) {
            for (KnowledgeBuilderError error: errors) {
                System.err.println(error);
            }
            throw new IllegalArgumentException("Could not parse knowledge.");
        }
        KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
        kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());
        return kbase;
    } 
}

RuleConfig.xml

 <change-set xmlns='http://drools.org/drools-5.0/change-set'
             xmlns:xs='http://www.w3.org/2001/XMLSchema-instance'
             xs:schemaLocation='http://drools.org/drools-5.0/change-set http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-api/src/main/resources/change-set-1.0.0.xsd' >
  <add>
       <resource source='classpath:RuleFile.drl' type='DRL' />
       <resource source='classpath:Sample.drl' type='DRL' />
   </add>
 </change-set>

Upvotes: 1

Views: 2857

Answers (1)

zenbeni
zenbeni

Reputation: 7223

Drools need that rules are ordered: so in your xml file change the order, your function myFunction() is not actually read yet by drools when it starts parsing RuleFile.drl: I think this is why you get the error. Sample.drl must be parsed before RuleFile.drl and the order in your XML file is important.

Upvotes: 1

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