[rules-users] Error in MVEL execution (optimization?)

ronalbury ronalbury at gmail.com
Thu Jan 5 08:55:46 EST 2012


Here is a very simple test.  Note that utilMethod is called twice for the
first rule, but is never called for the other two rules.  If you convert to
Java dialect then things execute as expected.


TestRules.drl:
#created on: Jan 5, 2012
package com.sample

import com.sample.TestUtility;

rule "First Rule"
    when
    	$tf : TestFact(TestUtility.utilMethod(s, "Value1") == true
    	          && i > 0
    	)
    then
        System.out.println("First Rule Fires");
end

rule "Second Rule"
    when
    	$tf : TestFact(TestUtility.utilMethod(s, "Value2") == true
    	          && i > 0
    	)
    then
        System.out.println("Second Rule Fires");
end

rule "Third Rule"
    when
    	$tf : TestFact(TestUtility.utilMethod(s, "Value3") == true
    	          && i > 0
    	)
    then
        System.out.println("Third Rule Fires");
end



TestUtility.java:
package com.sample;

public class TestUtility {
    public static Boolean utilMethod(String s1, String s2) {
        Boolean result = null;

        if (s1 != null) {
            result = s1.equals(s2);
        }

        System.out.println("in utilMethod >" + s1 + "<  >" + s2 + "< returns
" + result);
        return result;
    }
}

TestDriver.java:
    public static final void main(String[] args) {
        try {
            // load up the knowledge base
            KnowledgeBase kbase = readKnowledgeBase();
            StatefulKnowledgeSession ksession =
kbase.newStatefulKnowledgeSession();

            // setup the debug listeners
            ksession.addEventListener(new DebugAgendaEventListener());
            ksession.addEventListener(new
DebugWorkingMemoryEventListener());
            KnowledgeRuntimeLogger logger =
KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "test");

            // go !
            TestFact fact = new TestFact();
            fact.setS("asdf");
            fact.setI(10);
            ksession.insert(fact);
            ksession.fireAllRules();
            logger.close();
        }
        catch (Throwable t) {
            t.printStackTrace();
        }
    }


Output:
in utilMethod >asdf<  >Value1< returns false
in utilMethod >asdf<  >Value1< returns false
==>[ObjectInsertedEventImpl: getFactHandle()=[fact
0:1:31556811:31556811:1:DEFAULT:com.sample.TestFact at 1e184cb],
getObject()=com.sample.TestFact at 1e184cb,
getKnowledgeRuntime()=org.drools.impl.StatefulKnowledgeSessionImpl at 70610a,
getPropagationContext()=PropagationContextImpl [activeActivations=0,
dormantActivations=0, entryPoint=EntryPoint::DEFAULT, factHandle=[fact
0:1:31556811:31556811:1:DEFAULT:com.sample.TestFact at 1e184cb],
leftTuple=null, originOffset=-1, propagationNumber=3, rule=null, type=0]]


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