Simple Drools using Maven

Lets create a simple Drools example using Maven

• Open Eclipse IDE
• File -> New maven project
• choose the simple maven project
• enter the Group Id and Artifact Id as below
• Group ID    : com.droolstutorials.examples.drools
• Artifact ID  : Drools6.2Example
• click Finish.

A pom.xml will be created in the project .
Add the below dependencies to it.

    <dependencies>

        <dependency>

            <groupId>org.drools</groupId>

            <artifactId>drools-compiler</artifactId>

            <version>6.0.0.CR1</version>

        </dependency>

        <dependency>

            <groupId>org.drools</groupId>

            <artifactId>drools-core</artifactId>

            <version>6.0.0.CR1</version>

        </dependency>

    </dependencies>

Your final pom.xml will look like this. 







Lets create a Rule Executor file 
Lets first create a package as below 

• src.main.java.com.droolstutorials.examples.drools.controller

and then create the java file as

• RulesExecutor

RulesExecutor.java

package com.droolstutorials.examples.drools.controller;

import org.kie.api.KieServices;
import org.kie.api.builder.KieBuilder;
import org.kie.api.builder.KieFileSystem;
import org.kie.api.builder.KieRepository;
import org.kie.api.builder.Message.Level;
import org.kie.api.io.KieResources;
import org.kie.api.io.Resource;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;

public class RulesExecutor {
    public void runRules(String[] rules, Object[] employees) {
        KieServices kieServices = KieServices.Factory.get();
        KieResources kieResources = kieServices.getResources();
        KieFileSystem kieFileSystem = kieServices.newKieFileSystem();
        KieRepository kieRepository = kieServices.getRepository();

        for (String ruleFile : rules) {
            Resource resource = kieResources.newClassPathResource(ruleFile);
            kieFileSystem.write(
                    "src/main/resources/com/droolstutorials/examples/drools/"
                            + ruleFile, resource);
        }

        KieBuilder kb = kieServices.newKieBuilder(kieFileSystem);
        kb.buildAll();

        if (kb.getResults().hasMessages(Level.ERROR)) {
            throw new RuntimeException("Build Errors:\n"
                    + kb.getResults().toString());
        }

        KieContainer kContainer = kieServices.newKieContainer(kieRepository
                .getDefaultReleaseId());

        KieSession kSession = kContainer.newKieSession();

        for (Object emp : employees) {
            kSession.insert(emp);
        }

        System.out.println("rules int "+kSession.fireAllRules());

    }
}
 

Lets now create a package as below 

• src.main.java.com.droolstutorials.examples.drools.model

and then create the java file (model) as

• Employee

Employee.java 

package com.droolstutorials.examples.drools.model;

public class Employee {
    private String name;
    private String type;

    public Employee(String name, String type) {
        this.name = name;
        this.type = type;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getType() {
        return type;
    }

    public void setAge(String type) {
        this.type = type;
    }

}

Lets now create a package as below 

• src.main.resources

and then create the .drl file as

• Employee.drl

import com.droolstutorials.examples.drools.model.Employee

dialect "mvel"

rule "onsite"
    when
        $employee : Employee(type.equals("onsite"))             
    then
        System.out.println("onsite :: "+$employee.name);
    end

rule "name without a"  
    when
        $employee : Employee(!name.contains("a"))  
    then
        System.out.println("name without a :: "+$employee.name);
    end

Now its time for creating the Main class to test it.

Create the main class in the below locaton

• src.main.java.com.droolstutorials.examples.drools

Main.java

package com.droolstutorials.examples.drools;

import com.droolstutorials.examples.drools.controller.RulesExecutor;
import com.droolstutorials.examples.drools.model.Employee;
 
public class Main
{
    public static void main(String[] args)
    {
        RulesExecutor runner = new RulesExecutor();
        String valStr="";
        Employee naren = new Employee("Narendar", "onsite");
        Employee karthi = new Employee("KarthiK", "offshore");
        Employee ehfaj = new Employee("Ehfaj", "onsite");
        Employee bala = new Employee("Bala", "offshore");
        Employee pintu = new Employee("Pintu", "offshore");
               
        String[] rules = { "Employee.drl" };
        Object[] employees = {naren, karthi, ehfaj, bala, pintu};

        runner.runRules(rules,employees);
    }
} 

Now run the Main as java application and you can see the drools rules getting executed. 

Happy Drooling...