How to call a Drools Rule using Java integration tests

Question

I am writing a rule to determine the type of service that should be received based on the category of grievance.

I wrote a jUnit integration test to test the rule using a newly created java object called 'grievanceDTO'.

@Test
public class RuleTest {

    @Autowired
    private GrievanceRuleService grievanceRuleService;

    @Autowired
    public KieContainer kieContainer;

    @Test 
    public void calculateEligibility() {
        Long id = (long) 1;
        GrievanceDTO grievanceDTO = new GrievanceDTO(id,"NA", "Access/Availability", "NA", "NA", "NA", "NA", "NA");
        String serviceType = grievanceRuleService.determineGrievance(grievanceDTO);
        assertNotNull(serviceType);
    }
}

I wrote a service class to fire the rules.

@Service
public class GrievanceRuleService {

    @Autowired
    public KieContainer kieContainer;
    
    public String determineGrievance(GrievanceDTO grievanceDTO) {
        
        KieSession kieSession = kieContainer.newKieSession();
        kieSession.setGlobal("grievanceDTO", grievanceDTO);
        kieSession.insert(grievanceDTO);
        kieSession.fireAllRules();
        kieSession.dispose();

        return grievanceDTO.getServiceType();
        
    }
}

The jUnit test fails.

java.lang.NullPointerException at cm.grievance.rules.RuleTest.calculateEligibility(RuleTest.java:13)

I wrote a separate configuration class with a KieContainer bean, which I autowire to my service.

@Configuration
@EnableJpaRepositories
@ComponentScan("dm.vantage.producer.service")
public class RuleConfiguration {
    public static final String grivFile = "/src/main/resources/drools/GrievanceRules.drl";

    @Bean
    public KieContainer kieContainer() {
        KieServices kieServices = KieServices.Factory.get();
        
        KieFileSystem kieFileSystem = kieServices.newKieFileSystem();
        kieFileSystem.write(ResourceFactory.newClassPathResource(grivFile));
        KieBuilder kieBuilder = kieServices.newKieBuilder(kieFileSystem);
        kieBuilder.buildAll();
        KieModule kieModule = kieBuilder.getKieModule();
        
        return kieServices.newKieContainer(kieModule.getReleaseId());
    }

}

And finally, my rule (DRL) file, which I made as simple as possible for the purpose of testing.

package drools;
//generated from Decision Table
import cm.grievance.service.dto.GrievanceDTO;

rule "grievancesMap_10"
    when
        $grievances:GrievanceDTO($grievances.getCategory().equals("NA"))
    then
        $grievances.setServiceType("Timely Access");
end

I can add the dto, but basically it has 'category' as the fourth field and 'serviceType' as the third.

I don't know why I get a null pointer as I have tested this and it should be populating the return statement with some value.

Answer 1

I was able to figure out the issue. It was with this line of code.

 GrievanceDTO grievanceDTO = new GrievanceDTO(id,"NA", "Access/Availability", "NA", "NA", "NA", "NA", "NA");

Instead of this instantiation, I replaced the assignment of the variable using setter methods.