Drools5.4 Basic Example

Creating the Project

• Open Eclipse (Kepler)
• New -> Maven Project
• Simple Project
• Group Id: com.skills421.examples.drools
• Artifact Id: Drools5.4Example
• 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>Drools5.4Example</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-core</artifactId>
<version>5.4.0.CR1</version>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>knowledge-api</artifactId>
<version>5.4.0.CR1</version>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-compiler</artifactId>
<version>5.4.0.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 java.util.Collection;

import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseFactory;
import org.drools.builder.KnowledgeBuilder;
import org.drools.builder.KnowledgeBuilderFactory;
import org.drools.builder.ResourceType;
import org.drools.definition.KnowledgePackage;
import org.drools.io.ResourceFactory;
import org.drools.runtime.StatefulKnowledgeSession;

public class RuleRunner
{
public RuleRunner()
{
}

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

KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();

for (int i = 0; i < rules.length; i++)
{
String ruleFile = rules[i];
System.out.println(“Loading file: ” + ruleFile);
kbuilder.add(ResourceFactory.newClassPathResource(ruleFile, RuleRunner.class), ResourceType.DRL);
}

Collection<KnowledgePackage> pkgs = kbuilder.getKnowledgePackages();
kbase.addKnowledgePackages(pkgs);
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();

for (int i = 0; i < facts.length; i++)
{
Object fact = facts[i];
System.out.println(“Inserting fact: ” + fact);
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.drools5_4

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]
Loading file: test1.drl
Inserting fact: com.skills421.examples.drools.model.Person@5480e605
Jon Doe
[/code]