I am new to drools and jbpm
Just created a simple “Hello world” sample with drools version ‘8.44.0.Final’, Java 21
And it works fine:

Gradle dependencies:

implementation 'org.drools:drools-compiler:8.44.0.Final'
implementation 'org.drools:drools-core:8.44.0.Final'
implementation 'org.drools:drools-mvel:8.44.0.Final'

DRL:

rule "Hello world"
    when
    then        
            System.out.println("Hello DRL");
end

Run Class:

public class TestDRL
{
  public static void main(String[] args)
  {
    String filePath = "META-INF/rules/test.drl";
    InputStream inputStream = TestDRL.class.getClassLoader().getResourceAsStream(filePath);

    KieHelper kieHelper = new KieHelper();

    kieHelper.addResource(ResourceFactory.newInputStreamResource(inputStream), ResourceType.DRL);

    KieSession kieSession = kieHelper.build().newKieSession();
    kieSession.fireAllRules();
    kieSession.dispose();
  }
}

Then, I created a simple “Hello world” bpmn2 sample:

public class Testbpmn
{
  public static void main(String[] args)
  {
    String filePath = "META-INF/rules/test.bpmn2";
    InputStream inputStream = Testbpmn.class.getClassLoader().getResourceAsStream(filePath);

    KieHelper kieHelper = new KieHelper();

    kieHelper.addResource(ResourceFactory.newInputStreamResource(inputStream), ResourceType.BPMN2);

    KieSession kieSession = kieHelper.build().newKieSession();
    kieSession.startProcess("StartEvent_1");
    kieSession.dispose();
  }
}

But getting this exception:

Exception in thread "main" java.lang.RuntimeException: Unknown resource type: ResourceType = 'jBPM BPMN2 Language'
    at org.kie.internal.services.KieAssemblersImpl.addResourceBeforeRules(KieAssemblersImpl.java:48)
    at org.drools.compiler.builder.impl.CompositeKnowledgeBuilderImpl.buildAssemblerResourcesBeforeRules(CompositeKnowledgeBuilderImpl.java:182)
    at org.drools.compiler.builder.impl.CompositeKnowledgeBuilderImpl.build(CompositeKnowledgeBuilderImpl.java:112)
    at org.drools.compiler.builder.impl.CompositeKnowledgeBuilderImpl.build(CompositeKnowledgeBuilderImpl.java:104)
    at org.drools.compiler.kie.builder.impl.AbstractKieProject.buildKnowledgePackages(AbstractKieProject.java:270)
    at org.drools.compiler.kie.builder.impl.AbstractKieProject.buildKnowledgePackages(AbstractKieProject.java:216)
    at org.drools.compiler.kie.builder.impl.AbstractKieProject.verify(AbstractKieProject.java:80)
    at org.drools.compiler.kie.builder.impl.KieBuilderImpl.buildKieProject(KieBuilderImpl.java:282)
    at org.drools.compiler.kie.builder.impl.KieBuilderImpl.buildAll(KieBuilderImpl.java:248)
    at org.drools.compiler.kie.builder.impl.KieBuilderImpl.buildAll(KieBuilderImpl.java:195)
    at org.drools.compiler.kie.builder.impl.KieBuilderImpl.buildAll(KieBuilderImpl.java:201)
    at org.kie.internal.utils.KieHelper.getKieContainer(KieHelper.java:104)
    at org.kie.internal.utils.KieHelper.build(KieHelper.java:84)
    at org.kie.internal.utils.KieHelper.build(KieHelper.java:79)

Tried to add the jbpm dependencies of the latest version (In addition to the DRL dependencies):

implementation 'org.jbpm:jbpm-flow-builder:7.74.1.Final'
implementation 'org.jbpm:jbpm-bpmn2:7.74.1.Final'

But still getting the same issue.

I see that jbpm have dependency to drools, now if I remove my drools dependency, then the drools 7.74.1.Final seems not to be compatible with Java 21?