[FIXED] Spring dependency injection with duplicate beans and @Order annotation

Issue

I am moderately confused about the DI injection mechanism in Spring when having multiple beans with the same name/type. According to the exam slides from the Pivotal's "Core Spring" Course, Spring's behaviour with identical beans can be boiled down to:

• One can define same bean more than once
• Spring injects the bean defined last
• Using @Order, the loading mechanism (and thus, which bean is loaded last) can be modified

However, in the following example, Spring will ignore any @Order annotations and inject the bean from the Config class last mentioned in the @Import statement. I'm therefore wondering whether the order of config classes in the @Import annotation overrides any @Order annotations. Or do I miss another important point? Any hints are highly appreciated. Thanks Stack Overflow!

Main Configuration class

@Configuration
@Import({RogueConfig.class,RewardsConfig.class})
public class TestInfrastructureConfig {
  // nothing interesting here, just importing configs
}

RewardsConfig

@Configuration
@Order(1)
public class RewardsConfig {
    @Bean
    public RewardNetwork rewardNetwork() {
        System.out.println("This Bean has been loaded from: " + this.getClass().getName());
        return new RewardNetworkImpl(null, null, null);
    }
}

RogueConfig

@Configuration
@Order(2)
public class RogueConfig {
    @Bean
    public RewardNetwork rewardNetwork() {
        System.out.println("This Bean has been loaded from: " + this.getClass().getName());
        return new RewardNetworkImpl(null, null, null);
    }
}

Test class

public class RewardNetworkTests {

    ApplicationContext applicationContext;

    @BeforeEach
    void setUp() {
        applicationContext = SpringApplication.run(TestInfrastructureConfig.class);
    }

    @Test
    void injectingRewardNetworkBeanWithOrdering() {
        RewardNetwork rewardNetwork = applicationContext.getBean(RewardNetwork.class);
        assertNotNull(rewardNetwork);
    }
}

No matter what values I assign @Order, or if I use ordering at all, the result will always be:

This Bean has been loaded from: config.RewardsConfig$$EnhancerBySpringCGLIB$$62461c55

The only way to change this is to modify the Import annotation in my TestInfrastructureConfig like so:

@Import({RewardsConfig.class,RogueConfig.class}), which yields:

This Bean has been loaded from: config.RogueConfig$$EnhancerBySpringCGLIB$$6ca7bc89

I am wondering what needs to be done to allow the values defined in @Order to take any effect.

Solution

I've been able to get Spring to use the @Order annotations by loading the configurations directly ( i.e. without the detour through a @Configuration class using @Import):

@SpringJUnitConfig({RogueConfig.class, RewardsConfig.class})
public class CdiTest {

    @Test
    public void testCdiWithIdenticalBeans(@Autowired RewardNetwork rewardNetwork) {
        assertThat(rewardNetwork).isNotNull();
    }
}

With the @Order(2) annotation on the RogueConfig class, this bean got loaded last, as shown in stdout:

This Bean has been loaded from: config.RogueConfig$$EnhancerBySpringCGLIB$$552b937f

It seems that when using @Import in config classes it will load bean definitions in the order provided in the annotation, thus making any @Order annotations on the respective config classes useless.

Answered By - Mike Floyd