How to get Drools (Kie Session) running in a Netbeans Web-Project (No Maven)?

Question

For several days I'm trying to run Drools in Netbeans but it just doesn't work like I want it to. I even tried to get it working as a maven project but that didn't work as well. I describe what I do to create the project, hopefully someone can give me a hint.

First of i need it to work without maven because I'm restricted to not use it. But before I put it in the real project I want to test it.

So first I create a new project

1. File>New Project.. Wizard
2. Chose "Java Web" Categorie and use Projecttype "Webapplication"
3. Selection a tomcat 8 webserver and Java EE 7 Web
4. No Frameworks for now (later hibernate)

5. Create lib folder in project and putting following jars in it:

   • drools-compiler-6.4.0.Final.jar
   • drools-core-6.4.0.Final.jar
   • drools-decisiontables-6.4.0.Final.jar
   • drools-jsr94-6.4.0.Final.jar
   • drools-reteoo-6.4.0.Final.jar
   • knowledge-api-6.4.0.Final.jar
   • kie-api-6.4.0.Final.jar
   • kie-internal-6.4.0.Final.jar
   • kie-ci-6.4.0.Final.jar
   • mvel2-2.2.6.Final.jar
   • antlr-runtime-3.5.Final.jar

With this Setup I create classes (both in package: Drools) DroolsMain (test without webserver and gui for faster debugging)

public class DroolsMain {

    private static KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
    private static Collection<KnowledgePackage> pkgs;
    private static KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
    private static StatefulKnowledgeSession ksession;

    public static void main(final String[] args) {
        init();
        initMessageObject();
        fireRules();
    }

    private static void init() {
        String myRule = "import Drools.Message rule \"Hello World 2\" when message:Message (type==\"Test\") then System.out.println(\"Test, Drools!\"); end";       
        Resource myResource = ResourceFactory.newReaderResource((Reader) new StringReader(myRule));
        kbuilder.add(myResource, ResourceType.DRL);

        if(kbuilder.hasErrors()) {
            System.out.println(kbuilder.getErrors().toString());
            throw new RuntimeException("unable to compile dlr");
        }

        pkgs = kbuilder.getKnowledgePackages();

        kbase.addKnowledgePackages(pkgs);

        ksession = kbase.newStatefulKnowledgeSession();
    }

    private static void fireRules() {
        ksession.fireAllRules();
    }

    private static void initMessageObject() {
        Message msg = new Message();
        msg.setType("Test");
        ksession.insert(msg);
    }   
}

and the above used Message class

public class Message {
    private String type;
    private String message;

    public String getType() {
        return type;
    }

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

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }


}

I now can run that code and have a the message returned.

Now i wanted to try it with Kie...

i just comment the methods in DroolsMain main() method. and put a Kie method in like current Drools documentation p. 172-174 there:

private static void kieTest() {
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kContainer = kieServices.getKieClasspathContainer();

        StatelessKieSession kSession = kContainer.newStatelessKieSession();
        Applicant bob = new Applicant("Mr. Bob", 16);
        //assertTrue(bob.isValid());
        kSession.execute(bob);
        //assertFalse(bob.isValid());            
    }

I didn't put the Applicant.class in here becaus its just a bean with 3 attributes. Also I create DRL applicant.drl file:

package Drools "Is of valid age"
import Drools.Applicant

when
    $a : Applicant(age < 18)
then
    $a.setValid(false);
end;

So this obviously does not work because Kie has maven dependencies so i tried this: 1. Add directories: - DroolsTest/resources/ - DroolsTest/resources/META-INF - DroolsTest/resources/META-INF/maven - DroolsTest/resources/Drools 2. Create DroolsTest/resources/META-INFkmodule.xml

Content:

<?xml version="1.0" encoding="UTF-8"?>
<kmodule xmlns="http://www.drools.org/xsd/kmodule">
    <kbase name="Drools" packages="Drools">
        <ksession name="ksession-drools" />
    </kbase>
</kmodule>

3. Create DroolsTest/resources/META-INF/maven/pom.properties Content: (groupId my package name), (artifactId my project name)

   groupId=Drools artifactId=DroolsTest version=1

4. put drl file here: DroolsTest/resources/Drools/applicant.drl

Compiling this throws a RuntimeException:

Exception in thread "main" java.lang.RuntimeException: Cannot find a default KieSession
    at org.drools.compiler.kie.builder.impl.KieContainerImpl.findKieSessionModel(KieContainerImpl.java:555)
    at org.drools.compiler.kie.builder.impl.KieContainerImpl.newKieSession(KieContainerImpl.java:548)
    at org.drools.compiler.kie.builder.impl.KieContainerImpl.newKieSession(KieContainerImpl.java:531)
    at Drools.DroolsMain.kieTest(DroolsMain.java:43)
    at Drools.DroolsMain.main(DroolsMain.java:52)
C:\Users\...\AppData\Local\NetBeans\Cache\8.1\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 3 seconds)

Is there a solution to get Kiew working without maven or can I read in a file without it?

---

UPDATE:

I tried launes solution:

import java.io.File;
import org.kie.api.KieBase;
import org.kie.api.KieServices;
import org.kie.api.builder.KieBuilder;
import org.kie.api.builder.KieFileSystem;
import org.kie.api.builder.Results;
import org.kie.api.io.Resource;
import org.kie.api.runtime.KieContainer;
import org.kie.api.runtime.KieSession;

public class DroolsMain {
private void ntry() {
        KieServices kieServices = KieServices.Factory.get();
        KieFileSystem kfs = kieServices.newKieFileSystem();

        File rule = new File("src/main/resources/Drools/applicant.drl");
        Resource res = kieServices.getResources().newFileSystemResource(rule);
        kfs.write(res);
        KieBuilder kieBuilder = kieServices.newKieBuilder(kfs).buildAll();
        Results results = kieBuilder.getResults();

        System.out.println("---Messages---");
        System.out.println(results.getMessages());

        KieContainer kieContainer = kieServices.newKieContainer(kieServices.getRepository().getDefaultReleaseId());
        KieBase kieBase = kieContainer.getKieBase();
        KieSession kieSession = kieBase.newKieSession();
    }

public static void main(final String[] args) {
        DroolsMain dm = new DroolsMain();
        dm.ntry();
    }
}

I also added all jars from the drools distribution. Now it compiles and has no errors

Answer 1

That's how I do it, no maven, no XML:

public void build() throws Exception {
    KieServices kieServices = KieServices.Factory.get();
    KieFileSystem kfs = kieServices.newKieFileSystem();
    //...
    Resource res = ...; 
    kfs.write( "src/main/resources/simple.drl", res );
    KieBuilder kieBuilder = kieServices.newKieBuilder( kfs ).buildAll();
    Results results = kieBuilder.getResults();
    if( results.hasMessages( Message.Level.ERROR ) ){
        System.out.println( results.getMessages() );
        throw new IllegalStateException( "### errors ###" );
    }

    KieContainer kieContainer =
        kieServices.newKieContainer( kieServices.getRepository().getDefaultReleaseId() );

    KieBase kieBase = kieContainer.getKieBase();
    kieSession = kieBase.newKieSession();
}

I usually use a Resource such as

kieServices.getResources().newInputStreamResource( fis )

since reading from a file is more flexible.