Specify whether @Bean methods should get proxied in order to enforce bean lifecycle behavior, e.g. to return shared singleton bean instances even in case of direct @Bean method calls in user code. This feature requires method interception, implemented through a runtime-generated CGLIB subclass which comes with limitations such as the configuration class and its methods not being allowed to declare final.
The default is true, allowing for 'inter-bean references' via direct method calls within the configuration class as well as for external calls to this configuration's @Bean methods, e.g. from another configuration class. If this is not needed since each of this particular configuration's @Bean methods is self-contained and designed as a plain factory method for container use, switch this flag to false in order to avoid CGLIB subclass processing.
Turning off bean method interception effectively processes @Bean methods individually like when declared on non-@Configuration classes, a.k.a. "@Bean Lite Mode" (see @Bean's javadoc). It is therefore behaviorally equivalent to removing the @Configuration stereotype.

Method annotated with @Bean is called directly in a @Configuration where proxyBeanMethods set to false. Set proxyBeanMethods to true or use dependency injection.

@Configuration(proxyBeanMethods = false)
public class GenericConfiguration {
    
    @Bean
    public DogCage dogCage(){
        return new DogCage();
    }

    @Bean
    public AnimalCage animalEden(){
        AnimalCage animalCage = new AnimalCage();
        animalCage.addCage(dogCage());
        return animalCage;
    }
}

@Configuration(proxyBeanMethods = true)
public class ProxyConfiguration {

    @Bean
    public DogCage dogCage(){
        return new DogCage();
    }

    @Bean
    public AnimalCage animalEden(@Autowired List<Cage> cages){
        return new AnimalCage(cages);
    }
}

public class Tests {
    @Autowired
    private BeanFactory beanFactory;
    @Autowired
    private GenericConfiguration genericConfiguration;
    @Autowired
    private AnimalCage animalCage;
    @Autowired
    private DogCage dogCage;
    @Test
    public void runConfig() {
        log.info("configuration: {}", genericConfiguration); // 原始對象類型

        log.info("Configuration中的Bean: {}", genericConfiguration.dogCage() == genericConfiguration.dogCage()); // 兩次結果不一樣
        log.info("容器中的Bnea: {}", beanFactory.getBean(DogCage.class) == beanFactory.getBean(DogCage.class));// 從Spring容器中取值都是一樣的
        animalCage.cages.forEach(cage -> {
            if (cage instanceof DogCage) {
                log.info("dogCage : {} ", cage == dogCage); // 和上面的對象不一致，非單例
            }
        });
    }
}

public class Tests {
    @Test
    public void runConfig() {
        log.info("configuration: {}", proxyConfiguration); // 1、CGLIB代理的對象

        log.info("Configuration中的Bean: {}", proxyConfiguration.dogCage() == proxyConfiguration.dogCage()); // 2、兩次結果相同
        log.info("容器中的Bnea: {}", beanFactory.getBean(DogCage.class) == beanFactory.getBean(DogCage.class));// 3、從Spring容器中取值都是一樣的
        animalCage.cages.forEach(cage -> {
            if (cage instanceof DogCage) {
                log.info("dogCage : {} ", cage == dogCage); // 和上面的對象不一致，非單例
            }
        });
    }
}