java - 流口水中的功能库

我在同一个文件夹中有下面两个文件.RuleFile.drl是规则库，Sample.drl是函数库。当我尝试执行规则时，出现以下错误。

我不确定我缺少什么以及如何解决此错误。任何帮助是极大的赞赏。

文件：RuleFile.drl

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

文件：Sample.drl

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

我在Eclipse中以及在运行代码时收到以下错误消息。

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

Java代码：

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>

最佳答案

Drools需要对规则进行排序：因此在您的xml文件中更改顺序，开始解析RuleFile.drl时，Drools尚未真正读取您的函数myFunction（）：我想这就是您收到错误的原因。必须在RuleFile.drl之前分析Sample.drl，并且XML文件中的顺序很重要。