Lazy load spring bean

Question

If a bean is lazily loaded, Will all the beans defined inside the lazily loaded beans will be lazily loaded? (even though they are not defined @Lazy)

Here is the test project: https://github.com/madhur/conditional-property-test/blob/master/src/main/java/com/example/demo/EventPublishService.java

I have these beans:

@Service
@ConditionalOnProperty(
        name = {"publish.feed.events"},
        havingValue = "true"
)
public class EventPublishService {
 
     @Autowired
     private KafkaPublisher kafkaPublisher;

}

////////////////////

@Service
public class EventService {

    @Autowired
    @Lazy
    private EventPublishService eventPublishService;

    @Value("${publish.feed.events:false}")
    private boolean isPublishEvents;
}

/////////////////////////

@Component
public class KafkaPublisher {

    @Value("${kafka.producer.financial_feed.topic}")
    private String financeFeedTopic;
}

Any my application.properties has just one property,

publish.feed.events=false

Since , I am not loading EventPublishService beans(because the property is false), I expect the dependency bean KafkaPublisher should not be loaded as well. However, I get the error upon startup, which means the KafkaPublisher bean is getting loaded, even though EventPublishService bean is not getting loaded.

How can I ensure that KafkaPublisher bean should not be loaded? And thus property should not be mandatory required for anyone not requiring EventPublishService bean?

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'kafkaPublisher': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'kafka.producer.financial_feed.topic' in value "${kafka.producer.financial_feed.topic}"
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:379) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1344) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:578) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:501) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:760) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) [spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:395) [spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:327) [spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1255) [spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1243) [spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
        at com.example.demo.DemoApplication.main(DemoApplication.java:17) [main/:na] Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'kafka.producer.financial_feed.topic' in value "${kafka.producer.financial_feed.topic}"
        at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:172) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:124) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:237) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:211) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.lambda$processProperties$0(PropertySourcesPlaceholderConfigurer.java:175) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.resolveEmbeddedValue(AbstractBeanFactory.java:839) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1086) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1065) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:584) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:91) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:373) ~[spring-beans-5.0.5.RELEASE.jar:5.0.5.RELEASE]
        ... 16 common frames omitted

Answer 1

As stated in the doc,

Beans that are singleton-scoped and set to be pre-instantiated (the default) are created when the container is created

thus it doesn't matter if you put @Lazy on @Autowired, the bean will be created at startup as long as the bean itself is not defined lazy:

@Component
public class KafkaPublisher {
    ...
}

If you want this bean to be lazily initialized, put @Lazy on it. If you want the process of bean injection to be lazy, put @Lazy on @Autowired, as simple as that.

Lazily initializing a set of related beans could be achieved by declaring them inside a @Configuration class and marking configuration @Lazy. However, note that ALL of the declared beans will be initialized as soon as @Configuration class is initialized.

@Lazy
@Configuration
@ComponentScan(...) // will be lazily initialized with config
public class LazyConfiguration {

    @Bean
    public SomeBean beanName() { // will be lazily initialized with config
        return new SomeBean();
    } 

    @Bean
    public OtherBean beanName() { // will be lazily initialized with config
        return new OtherBean();
    }     
}

However, when using @ComponentScan, make sure the beans (i.e @Service, @Component, etc) you want to initialize lazily are not already scanned by some other context. If they are, add them as exclusions to scanning for that context.

---

Outdated answer down below, for historical purposes (before OP completely changed the question):

Declaring beans inside beans is not considered to be a good practice, but if you mark a @Configuration as lazy, then indeed all the beans inside of it will be lazily initialized, as stated in @Lazy's javadoc:

If Lazy is present on a @Configuration class, this indicates that all @Bean methods within that @Configuration should be lazily initialized.

If by "beans defined inside" you actually mean injection points, such as @Autowired, javadoc has the answer for that as well:

Lazy annotation may also be placed on injection points marked with Autowired or Inject: In that context, it leads to the creation of a lazy-resolution proxy for all affected dependencies, as an alternative to using ObjectFactory or Provider.

However, the actual autowired bean will be initialized eagerly (if not marked as @Lazy as well). It's the injection itself that will be lazy in this case.

Otherwise, please clarify what you mean.