Axon Framework: Aggregate Autowired Bean throws NullPointerException in Test

Question

Springboot and Axon: Basically I am unit testing an aggregate that uses three different ObjectMapper instances, each with a different configuration. These are defined in config class :

    @Configuration
    public class JacksonConfiguration {

    @Bean(name="flatMapper")
    @Primary
    public ObjectMapper flatMapper(){
        return new ObjectMapper();
    }

    @Bean(name="unknownPropertiesMapper")
    public ObjectMapper unknownPropertiesMapper(){
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        return mapper;
    }

    @Bean(name="nullPropertiesMapper")
    public ObjectMapper nullPropertiesMapper(){
        ObjectMapper mapper = new ObjectMapper();
        mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        return mapper;
    }

}

They are injected and used in my aggregate as follow:

@Aggregate
@Data
@Component
public class MyAggregate {

    @Autowired
    @Qualifier("flatMapper")
    private ObjectMapper flatMapper;

    @Autowired
    @Qualifier("unknownPropertiesMapper")
    private ObjectMapper unknownPropertiesMapper;

    @Autowired
    @Qualifier("nullPropertiesMapper")
    private ObjectMapper nullPropertiesMapper;


    @AggregateIdentifier
    private String id;

  //Methods and Handlers: a method is using "unknownPropertiesMapper" is "changedKeySet" 

when I run SpringBootApplication everything is properly instanciated and working as expected, but when testing I get NullPointerException over thier instances:

@ContextConfiguration(classes = JacksonConfiguration.class)
@SpringBootTest(classes = OccurrenceAggregate.class)
@ComponentScan(basePackageClasses = MyAggregate.class)
public class AggregateTest {
    
    private FixtureConfiguration<MyAggregate> fixture;

    @BeforeEach
    public void setUp() {
        fixture = new AggregateTestFixture<>(MyAggregate.class);
    }

    @Test
    public void myTest() {

       fixture.givenNoPriorActivity().... 

    }

test console:

org.axonframework.test.AxonAssertionError: The command handler threw an unexpected exception

Expected <ANYTHING> but got <exception of type [NullPointerException]>. Stack trace follows:
java.lang.NullPointerException
    at com.example.business.aggregates.MyAggregate.changedKeySet(MyAggregate.java:185)

changedKeySet() is throwing NPE because its using unknownPropertiesMapper and it is value is null. as I mentionned it works fine when I run the Main class but not in tests (Junit5).

Answer 1

The Aggregate is not set up correctly. The correct way to inject a Spring Bean into the Aggregate is to add it to the CommandHandler method.

@CommandHandler
    public void handle(ACommand cmd, ObjectMapper flatMapper) {

In the test fixture you can inject it this way:

fixture.registerInjectableResource(flatMapper);