@Configuration
public class JavaConfig01 {
}
@Component
public class JavaConfig02 {
}

<context:component-scan 
base-package="org.javaboy.demo.p6"/>

public class Demo {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans_demo.xml");
        JavaConfig01 config01 = ctx.getBean(JavaConfig01.class);
        JavaConfig02 config02 = ctx.getBean(JavaConfig02.class);
        System.out.println("config01.getClass() = " + config01.getClass());
        System.out.println("config02.getClass() = " + config02.getClass());
    }
}

@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
	int registryId = System.identityHashCode(registry);
	if (this.registriesPostProcessed.contains(registryId)) {
		throw new IllegalStateException(
				"postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
	}
	if (this.factoriesPostProcessed.contains(registryId)) {
		throw new IllegalStateException(
				"postProcessBeanFactory already called on this post-processor against " + registry);
	}
	this.registriesPostProcessed.add(registryId);
	processConfigBeanDefinitions(registry);
}

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
	List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
	String[] candidateNames = registry.getBeanDefinitionNames();
	for (String beanName : candidateNames) {
		BeanDefinition beanDef = registry.getBeanDefinition(beanName);
		if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
			if (logger.isDebugEnabled()) {
				logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
			}
		}
		else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
			configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
		}
	}
	//省略。。。
}

static boolean checkConfigurationClassCandidate(
		BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
        //省略。。。
	Map<String, Object> config = metadata.getAnnotationAttributes(Configuration.class.getName());
	if (config != null && !Boolean.FALSE.equals(config.get("proxyBeanMethods"))) {
		beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
	}
	else if (config != null || isConfigurationCandidate(metadata)) {
		beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
	}
	else {
		return false;
	}
    //省略
}

static boolean isConfigurationCandidate(AnnotationMetadata metadata) {
	// Do not consider an interface or an annotation...
	if (metadata.isInterface()) {
		return false;
	}
	// Any of the typical annotations found?
	for (String indicator : candidateIndicators) {
		if (metadata.isAnnotated(indicator)) {
			return true;
		}
	}
	// Finally, let's look for @Bean methods...
	return hasBeanMethods(metadata);
}

/**
 * Prepare the Configuration classes for servicing bean requests at runtime
 * by replacing them with CGLIB-enhanced subclasses.
 */
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
	int factoryId = System.identityHashCode(beanFactory);
	if (this.factoriesPostProcessed.contains(factoryId)) {
		throw new IllegalStateException(
				"postProcessBeanFactory already called on this post-processor against " + beanFactory);
	}
	this.factoriesPostProcessed.add(factoryId);
	if (!this.registriesPostProcessed.contains(factoryId)) {
		// BeanDefinitionRegistryPostProcessor hook apparently not supported...
		// Simply call processConfigurationClasses lazily at this point then.
		processConfigBeanDefinitions((BeanDefinitionRegistry) beanFactory);
	}
	enhanceConfigurationClasses(beanFactory);
	beanFactory.addBeanPostProcessor(new ImportAwareBeanPostProcessor(beanFactory));
}

public void enhanceConfigurationClasses(ConfigurableListableBeanFactory beanFactory) {
	StartupStep enhanceConfigClasses = this.applicationStartup.start("spring.context.config-classes.enhance");
	Map<String, AbstractBeanDefinition> configBeanDefs = new LinkedHashMap<>();
	for (String beanName : beanFactory.getBeanDefinitionNames()) {
		BeanDefinition beanDef = beanFactory.getBeanDefinition(beanName);
		Object configClassAttr = beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE);
		if ((configClassAttr != null || methodMetadata != null) &&
				(beanDef instanceof AbstractBeanDefinition abd) && !abd.hasBeanClass()) {
			// Configuration class (full or lite) or a configuration-derived @Bean method
			// -> eagerly resolve bean class at this point, unless it's a 'lite' configuration
			// or component class without @Bean methods.
			boolean liteConfigurationCandidateWithoutBeanMethods =
					(ConfigurationClassUtils.CONFIGURATION_CLASS_LITE.equals(configClassAttr) &&
						annotationMetadata != null && !ConfigurationClassUtils.hasBeanMethods(annotationMetadata));
			if (!liteConfigurationCandidateWithoutBeanMethods) {
				try {
					abd.resolveBeanClass(this.beanClassLoader);
				}
			}
		}
		if (ConfigurationClassUtils.CONFIGURATION_CLASS_FULL.equals(configClassAttr)) {
			configBeanDefs.put(beanName, abd);
		}
	}
	ConfigurationClassEnhancer enhancer = new ConfigurationClassEnhancer();
	for (Map.Entry<String, AbstractBeanDefinition> entry : configBeanDefs.entrySet()) {
		AbstractBeanDefinition beanDef = entry.getValue();
		// If a @Configuration class gets proxied, always proxy the target class
		beanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
		// Set enhanced subclass of the user-specified bean class
		Class<?> configClass = beanDef.getBeanClass();
		Class<?> enhancedClass = enhancer.enhance(configClass, this.beanClassLoader);
		if (configClass != enhancedClass) {
			beanDef.setBeanClass(enhancedClass);
		}
	}
	enhanceConfigClasses.tag("classCount", () -> String.valueOf(configBeanDefs.keySet().size())).end();
}

public Class<?> enhance(Class<?> configClass, @Nullable ClassLoader classLoader) {
	if (EnhancedConfiguration.class.isAssignableFrom(configClass)) {
		return configClass;
	}
	Class<?> enhancedClass = createClass(newEnhancer(configClass, classLoader));
	return enhancedClass;
}
private Enhancer newEnhancer(Class<?> configSuperClass, @Nullable ClassLoader classLoader) {
	Enhancer enhancer = new Enhancer();
	enhancer.setSuperclass(configSuperClass);
	enhancer.setInterfaces(new Class<?>[] {EnhancedConfiguration.class});
	enhancer.setUseFactory(false);
	enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
	enhancer.setAttemptLoad(true);
	enhancer.setStrategy(new BeanFactoryAwareGeneratorStrategy(classLoader));
	enhancer.setCallbackFilter(CALLBACK_FILTER);
	enhancer.setCallbackTypes(CALLBACK_FILTER.getCallbackTypes());
	return enhancer;
}

private static class BeanMethodInterceptor implements MethodInterceptor, ConditionalCallback {
	@Override
	@Nullable
	public Object intercept(Object enhancedConfigInstance, Method beanMethod, Object[] beanMethodArgs,
				MethodProxy cglibMethodProxy) throws Throwable {
		ConfigurableBeanFactory beanFactory = getBeanFactory(enhancedConfigInstance);
		String beanName = BeanAnnotationHelper.determineBeanNameFor(beanMethod);
		// Determine whether this bean is a scoped-proxy
		if (BeanAnnotationHelper.isScopedProxy(beanMethod)) {
			String scopedBeanName = ScopedProxyCreator.getTargetBeanName(beanName);
			if (beanFactory.isCurrentlyInCreation(scopedBeanName)) {
				beanName = scopedBeanName;
			}
		}
		// To handle the case of an inter-bean method reference, we must explicitly check the
		// container for already cached instances.
		// First, check to see if the requested bean is a FactoryBean. If so, create a subclass
		// proxy that intercepts calls to getObject() and returns any cached bean instance.
		// This ensures that the semantics of calling a FactoryBean from within @Bean methods
		// is the same as that of referring to a FactoryBean within XML. See SPR-6602.
		if (factoryContainsBean(beanFactory, BeanFactory.FACTORY_BEAN_PREFIX + beanName) &&
				factoryContainsBean(beanFactory, beanName)) {
			Object factoryBean = beanFactory.getBean(BeanFactory.FACTORY_BEAN_PREFIX + beanName);
			if (factoryBean instanceof ScopedProxyFactoryBean) {
				// Scoped proxy factory beans are a special case and should not be further proxied
			}
			else {
				// It is a candidate FactoryBean - go ahead with enhancement
				return enhanceFactoryBean(factoryBean, beanMethod.getReturnType(), beanFactory, beanName);
			}
		}
		if (isCurrentlyInvokedFactoryMethod(beanMethod)) {
			return cglibMethodProxy.invokeSuper(enhancedConfigInstance, beanMethodArgs);
		}
		return resolveBeanReference(beanMethod, beanMethodArgs, beanFactory, beanName);
	}
}

@Configuration
public class JavaConfig {
    @Bean
    User user() {
        User user = new User();
        user.setDog(dog());
        return user;
    }
    @Bean
    Dog dog() {
        return new Dog();
    }
}