Hi,

Using Rules in our workflow saves us the trouble of creating Sessions and firing rules explicitly. Everything is done automatically. Sharing an example on using rules in jbpm 4 workflow.

1) Process Definition :

<?xml version="1.0" encoding="UTF-8"?>

<process key="rules" name="TestRules" xmlns="http://jbpm.org/4.3/jpdl">

   <start g="133,0,48,48" name="start1">

      <transition to="Rule"/>

   </start>

   <rules g="60,84,193,73" name="Rule">

   <fact var="check"/>

      <transition to="exclusive1"/>

   </rules>

   <decision expr="#{check.decision}" g="132,192,75,58" name="exclusive1">

      <transition g="-30,-14" name="Yes" to="java1"/>

      <transition g="8,-12" name="No" to="java2"/>

   </decision>

   <java class="action.Print" g="36,252,85,49" method="printYes" name="java1">

      <transition to="end1"/>

   </java>

   <java class="action.Print" g="192,252,84,49" method="printNo" name="java2">

      <transition to="end1"/>

   </java>

   <end g="132,324,55,53" name="end1"/>

</process>

Process Definition here consists of a Rule node which matches the fact "check" with the rules in .drl file. Following which the value of the class variable decision is matched and accordingly a transition is taken up by the workflow.

2) Rule Resource :

import action.Customer;

rule "CheckAge1"

  when

    customer : Customer( age >= 18)

  then

      System.out.println("INSIDE RULE CHECKAGE1");

    customer.setDecision("Yes");

end

rule "CheckAge2"

  when

    customer : Customer( age < 18)

  then

      System.out.println("INSIDE RULE CHECKAGE2");

    customer.setDecision("No");

end

3) POJO :

package action;

import java.io.Serializable;

public class Customer implements Serializable {

     int age;

     String decision="Yes";

    Customer(int age)

    {

        this.age = age;

    }

    public int getAge()

    {

        return age;

    }

    public void setAge(int age)

    {

        this.age = age;

    }

    public String getDecision()

    {

        return decision;

    }

    public void setDecision(String decision)

    {

        this.decision = decision;

    }

}

4) Main Class :

package action;

import java.util.HashMap;

import java.util.Map;

import org.jbpm.api.Configuration;

import org.jbpm.api.ExecutionService;

import org.jbpm.api.ProcessEngine;

import org.jbpm.api.RepositoryService;

public class StartRulesProcess {

    public static void main(String[] args) {

        Configuration configuration = new Configuration();

        ProcessEngine processEngine = configuration.buildProcessEngine();

        RepositoryService repositoryService = processEngine.getRepositoryService();

        ExecutionService executionService = processEngine.getExecutionService();

        repositoryService.createDeployment().addResourceFromClasspath("Rule.drl").addResourceFromClasspath("TestRules.jpdl.xml").deploy();

    //    repositoryService.createDeployment().addResourceFromClasspath("TestRules.jpdl.xml").deploy();

        Map<String, Object> var = new HashMap<String, Object>();

        var.put("check", new Customer(19));

        executionService.startProcessInstanceByKey("rules", var);   

    }

}

Regards