Drools6.0 Basic Example

This post has been updated to the very latest Drools6.x – the new post can be found here: Drools6.x Basic Example

Creating the Project

• Open Eclipse (Kepler)
• New -> Maven Project
• Simple Project
• Group Id: com.skills421.examples.drools
• Artifact Id: Drools6.0Example
• Finish

pom.xml

[code language=”xml”]
<project xmlns=”http://maven.apache.org/POM/4.0.0″ xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance” xsi:schemaLocation=”http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd”>
<modelVersion>4.0.0</modelVersion>
<groupId>com.skills421.examples.drools</groupId>
<artifactId>Drools6.0Example</artifactId>
<version>0.0.1-SNAPSHOT</version>
<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>
</project>
[/code]

Rule Runner

src/main/java
com.skills421.examples.drools.controller.RuleRunner

[code language=”java”]
package com.skills421.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 RuleRunner
{
public RuleRunner()
{
}

public void runRules(String[] rules, Object[] facts)
{

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);

// path has to start with src/main/resources
// append it with the package from the rule
kieFileSystem.write(“src/main/resources/com/skills421/examples/drools6_0/”+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 fact : facts)
{
kSession.insert(fact);
}

kSession.fireAllRules();
}
}
[/code]

Person

src/main/java
com.skills421.examples.drools.model.Person

[code language=”java”]
package com.skills421.examples.drools.model;

public class Person
{
private String name;
private int age;

public Person()
{

}

public Person(String name, int age)
{
this.name = name;
this.age = age;
}

public String getName()
{
return name;
}

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

public int getAge()
{
return age;
}

public void setAge(int age)
{
this.age = age;
}

}
[/code]

Main

src/main/java
com.skills421.examples.drools.Main

[code language=”java”]
package com.skills421.examples.drools;

import com.skills421.examples.drools.controller.RuleRunner;
import com.skills421.examples.drools.model.Person;

public class Main
{
public static void main(String[] args)
{
RuleRunner runner = new RuleRunner();

String[] rules = { “test1.drl” };
Object[] facts = { new Person(“Jon Doe”, 21) };

runner.runRules(rules,facts);
}
}
[/code]

Rules

src/main/resources
test1.drl

[code language=”java”]
package com.skills421.examples.drools6_0

import com.skills421.examples.drools.model.Person

dialect “mvel”

/*
* This rule checks that a person is >= 21
*/
rule “Person is 21”
when
$person : Person(age>=21)
then
System.out.println($person.name);
end
[/code]

Output

[code]
Jon Doe
[/code]