Drools KieSession example

Drools KieSession example

Drools 6.0 onwards a new approach is designed to create a Knowledge Base and a Knowledge Session compared to previous versions.

The below example will explain on how to create a Default KieSession

The Drools 6.0 project consists of a single meta data file META-INF/kmodule.xml. The file is located under the source folder as shown in below snapshot.


If the file is not located at the location

KieSession ksession = 

kc.newKieSession();

// will return null

By default, kc.newKieSession() returns the object of org.drools.core.impl.StatefulKnowledgeSessionImpl class.

Below are the files that are required to fire the rules using KieSession

kmodule.xml file - Since we are creating a default KieSession, no need to define any kbase

<?xml version="1.0" encoding="UTF-8"?>
<kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://jboss.org/kie/6.0.0/kmodule">
</kmodule>

DRL File

package com.sample
 
import com.pojo.*;
 
rule "Check Circuit Limit"
when
 $stock : Stock()
then
 $stock.setHaltTrading(true);
 System.out.println("Rule Fired using KIE Default Session");
end

Client File

package com.sample;

import org.kie.api.KieServices;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;
import org.kie.internal.KnowledgeBase;

import com.pojo.Stock;

/**
 * This is a sample class to launch a rule.
 */
public class DroolsTest {

 public static final void main(String[] args) {
  try {
   KieServices ks = KieServices.Factory.get();

   KieContainer kc = ks.getKieClasspathContainer();

   KieSession ksession = kc.newKieSession();
   System.out.println("KieSession - " +ksession);
   final Stock a = new Stock();

   ksession.insert(a);

   ksession.fireAllRules();

   ksession.dispose(); // Stateful rule session must always be disposed
   // when finished
  } catch (Throwable t) {
   t.printStackTrace();
  }
 }

}

Output:

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
KieSession - org.drools.core.impl.StatefulKnowledgeSessionImpl@cab854
Rule Fired using KIE Default Session