@Override
public Object getBean(String name) throws BeansException {
	String beanName = BeanFactoryUtils.transformedBeanName(name);
	Object bean = this.beans.get(beanName);

	if (bean == null) {
		throw new NoSuchBeanDefinitionException(beanName,
				"Defined beans are [" + StringUtils.collectionToCommaDelimitedString(this.beans.keySet()) + "]");
	}

	// Don't let calling code try to dereference the
	// bean factory if the bean isn't a factory
	if (BeanFactoryUtils.isFactoryDereference(name) && !(bean instanceof FactoryBean)) {
		throw new BeanIsNotAFactoryException(beanName, bean.getClass());
	}

	if (bean instanceof FactoryBean && !BeanFactoryUtils.isFactoryDereference(name)) {
		try {
			Object exposedObject = ((FactoryBean<?>) bean).getObject();
			if (exposedObject == null) {
				throw new BeanCreationException(beanName, "FactoryBean exposed null object");
			}
			return exposedObject;
		}
		catch (Exception ex) {
			throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
		}
	}
	else {
		return bean;
	}
}
 

@Override
public Object getBean(String name) throws BeansException {
	String beanName = BeanFactoryUtils.transformedBeanName(name);
	Object bean = this.beans.get(beanName);

	if (bean == null) {
		throw new NoSuchBeanDefinitionException(beanName,
				"Defined beans are [" + StringUtils.collectionToCommaDelimitedString(this.beans.keySet()) + "]");
	}

	// Don't let calling code try to dereference the
	// bean factory if the bean isn't a factory
	if (BeanFactoryUtils.isFactoryDereference(name) && !(bean instanceof FactoryBean)) {
		throw new BeanIsNotAFactoryException(beanName, bean.getClass());
	}

	if (bean instanceof FactoryBean && !BeanFactoryUtils.isFactoryDereference(name)) {
		try {
			Object exposedObject = ((FactoryBean<?>) bean).getObject();
			if (exposedObject == null) {
				throw new BeanCreationException(beanName, "FactoryBean exposed null object");
			}
			return exposedObject;
		}
		catch (Exception ex) {
			throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
		}
	}
	else {
		return bean;
	}
}
 

/**
 * Get the object for the given bean instance, either the bean
 * instance itself or its created object in case of a FactoryBean.
 * @param beanInstance the shared bean instance
 * @param name name that may include factory dereference prefix
 * @param beanName the canonical bean name
 * @param mbd the merged bean definition
 * @return the object to expose for the bean
 */
protected Object getObjectForBeanInstance(
		Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {

	// Don't let calling code try to dereference the factory if the bean isn't a factory.
	if (BeanFactoryUtils.isFactoryDereference(name)) {
		if (beanInstance instanceof NullBean) {
			return beanInstance;
		}
		if (!(beanInstance instanceof FactoryBean)) {
			throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
		}
	}

	// Now we have the bean instance, which may be a normal bean or a FactoryBean.
	// If it's a FactoryBean, we use it to create a bean instance, unless the
	// caller actually wants a reference to the factory.
	if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
		return beanInstance;
	}

	Object object = null;
	if (mbd == null) {
		object = getCachedObjectForFactoryBean(beanName);
	}
	if (object == null) {
		// Return bean instance from factory.
		FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
		// Caches object obtained from FactoryBean if it is a singleton.
		if (mbd == null && containsBeanDefinition(beanName)) {
			mbd = getMergedLocalBeanDefinition(beanName);
		}
		boolean synthetic = (mbd != null && mbd.isSynthetic());
		object = getObjectFromFactoryBean(factory, beanName, !synthetic);
	}
	return object;
}
 

@Override
public Object getBean(String name) throws BeansException {
	String beanName = BeanFactoryUtils.transformedBeanName(name);
	Object bean = this.beans.get(beanName);

	if (bean == null) {
		throw new NoSuchBeanDefinitionException(beanName,
				"Defined beans are [" + StringUtils.collectionToCommaDelimitedString(this.beans.keySet()) + "]");
	}

	// Don't let calling code try to dereference the
	// bean factory if the bean isn't a factory
	if (BeanFactoryUtils.isFactoryDereference(name) && !(bean instanceof FactoryBean)) {
		throw new BeanIsNotAFactoryException(beanName, bean.getClass());
	}

	if (bean instanceof FactoryBean && !BeanFactoryUtils.isFactoryDereference(name)) {
		try {
			return ((FactoryBean<?>) bean).getObject();
		}
		catch (Exception ex) {
			throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
		}
	}
	else {
		return bean;
	}
}
 

/**
 * Get the object for the given bean instance, either the bean
 * instance itself or its created object in case of a FactoryBean.
 * @param beanInstance the shared bean instance
 * @param name name that may include factory dereference prefix
 * @param beanName the canonical bean name
 * @param mbd the merged bean definition
 * @return the object to expose for the bean
 */
protected Object getObjectForBeanInstance(
		Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {

	// Don't let calling code try to dereference the factory if the bean isn't a factory.
	if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
		throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
	}

	// Now we have the bean instance, which may be a normal bean or a FactoryBean.
	// If it's a FactoryBean, we use it to create a bean instance, unless the
	// caller actually wants a reference to the factory.
	if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
		return beanInstance;
	}

	Object object = null;
	if (mbd == null) {
		object = getCachedObjectForFactoryBean(beanName);
	}
	if (object == null) {
		// Return bean instance from factory.
		FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
		// Caches object obtained from FactoryBean if it is a singleton.
		if (mbd == null && containsBeanDefinition(beanName)) {
			mbd = getMergedLocalBeanDefinition(beanName);
		}
		boolean synthetic = (mbd != null && mbd.isSynthetic());
		object = getObjectFromFactoryBean(factory, beanName, !synthetic);
	}
	return object;
}
 

@Override
public Object getBean(String name) throws BeansException {
	String beanName = BeanFactoryUtils.transformedBeanName(name);
	Object bean = this.beans.get(beanName);

	if (bean == null) {
		throw new NoSuchBeanDefinitionException(beanName,
				"Defined beans are [" + StringUtils.collectionToCommaDelimitedString(this.beans.keySet()) + "]");
	}

	// Don't let calling code try to dereference the
	// bean factory if the bean isn't a factory
	if (BeanFactoryUtils.isFactoryDereference(name) && !(bean instanceof FactoryBean)) {
		throw new BeanIsNotAFactoryException(beanName, bean.getClass());
	}

	if (bean instanceof FactoryBean && !BeanFactoryUtils.isFactoryDereference(name)) {
		try {
			return ((FactoryBean<?>) bean).getObject();
		}
		catch (Exception ex) {
			throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
		}
	}
	else {
		return bean;
	}
}
 

/**
 * Get the object for the given bean instance, either the bean
 * instance itself or its created object in case of a FactoryBean.
 * @param beanInstance the shared bean instance
 * @param name name that may include factory dereference prefix
 * @param beanName the canonical bean name
 * @param mbd the merged bean definition
 * @return the object to expose for the bean
 */
protected Object getObjectForBeanInstance(
		Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {

	// Don't let calling code try to dereference the factory if the bean isn't a factory.
	if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
		throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
	}

	// Now we have the bean instance, which may be a normal bean or a FactoryBean.
	// If it's a FactoryBean, we use it to create a bean instance, unless the
	// caller actually wants a reference to the factory.
	if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
		return beanInstance;
	}

	Object object = null;
	if (mbd == null) {
		object = getCachedObjectForFactoryBean(beanName);
	}
	if (object == null) {
		// Return bean instance from factory.
		FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
		// Caches object obtained from FactoryBean if it is a singleton.
		if (mbd == null && containsBeanDefinition(beanName)) {
			mbd = getMergedLocalBeanDefinition(beanName);
		}
		boolean synthetic = (mbd != null && mbd.isSynthetic());
		object = getObjectFromFactoryBean(factory, beanName, !synthetic);
	}
	return object;
}
 

@Override
public Object getBean(String name) throws BeansException {
	String beanName = BeanFactoryUtils.transformedBeanName(name);
	Object bean = this.beans.get(beanName);

	if (bean == null) {
		throw new NoSuchBeanDefinitionException(beanName,
				"Defined beans are [" + StringUtils.collectionToCommaDelimitedString(this.beans.keySet()) + "]");
	}

	// Don't let calling code try to dereference the
	// bean factory if the bean isn't a factory
	if (BeanFactoryUtils.isFactoryDereference(name) && !(bean instanceof FactoryBean)) {
		throw new BeanIsNotAFactoryException(beanName, bean.getClass());
	}

	if (bean instanceof FactoryBean && !BeanFactoryUtils.isFactoryDereference(name)) {
		try {
			return ((FactoryBean<?>) bean).getObject();
		}
		catch (Exception ex) {
			throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
		}
	}
	else {
		return bean;
	}
}
 

/**
 * Get the object for the given bean instance, either the bean
 * instance itself or its created object in case of a FactoryBean.
 * @param beanInstance the shared bean instance
 * @param name name that may include factory dereference prefix
 * @param beanName the canonical bean name
 * @param mbd the merged bean definition
 * @return the object to expose for the bean
 */
protected Object getObjectForBeanInstance(
		Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {

	// Don't let calling code try to dereference the factory if the bean isn't a factory.
	if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
		throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
	}

	// Now we have the bean instance, which may be a normal bean or a FactoryBean.
	// If it's a FactoryBean, we use it to create a bean instance, unless the
	// caller actually wants a reference to the factory.
	if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
		return beanInstance;
	}

	Object object = null;
	if (mbd == null) {
		object = getCachedObjectForFactoryBean(beanName);
	}
	if (object == null) {
		// Return bean instance from factory.
		FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
		// Caches object obtained from FactoryBean if it is a singleton.
		if (mbd == null && containsBeanDefinition(beanName)) {
			mbd = getMergedLocalBeanDefinition(beanName);
		}
		boolean synthetic = (mbd != null && mbd.isSynthetic());
		object = getObjectFromFactoryBean(factory, beanName, !synthetic);
	}
	return object;
}
 

/**
 * Get the object for the given bean instance, either the bean
 * instance itself or its created object in case of a FactoryBean.
 * @param beanInstance the shared bean instance
 * @param name name that may include factory dereference prefix
 * @param beanName the canonical bean name
 * @param mbd the merged bean definition
 * @return the object to expose for the bean
 */
protected Object getObjectForBeanInstance(
		Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {

	// Don't let calling code try to dereference the factory if the bean isn't a factory.
	// 注释 4.6 如果 beanName 前缀是 & 符号
	if (BeanFactoryUtils.isFactoryDereference(name)) {
		if (beanInstance instanceof NullBean) {
			// 如果是 nullBean，第一次看到这种空的 bean =-=
			return beanInstance;
		}
		if (!(beanInstance instanceof FactoryBean)) {
			// 如果不是空 bean，又不是工厂 bean，报错
			throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
		}
	}

	// Now we have the bean instance, which may be a normal bean or a FactoryBean.
	// If it's a FactoryBean, we use it to create a bean instance, unless the
	// caller actually wants a reference to the factory.
	// 如果不是工厂 bean，或者带有 & 符号前缀，返回自己本身的类（可以返回工厂实例）
	if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
		return beanInstance;
	}
	// 加载工厂 bean
	Object object = null;
	if (mbd == null) {
		// 先从缓存中获取
		object = getCachedObjectForFactoryBean(beanName);
	}
	if (object == null) {
		// Return bean instance from factory.
		// 到了这一步，很确定是工厂 bean 类型了，通过 getObject 方法实例化 bean
		FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
		// Caches object obtained from FactoryBean if it is a singleton.
		// 尝试从单例缓存中获取
		if (mbd == null && containsBeanDefinition(beanName)) {
			mbd = getMergedLocalBeanDefinition(beanName);
		}
		// 是否是用户自定义的工厂 bean
		boolean synthetic = (mbd != null && mbd.isSynthetic());
		object = getObjectFromFactoryBean(factory, beanName, !synthetic);
	}
	return object;
}
 

/**
 * It should be illegal to dereference a normal bean as a factory.
 */
@Test(expected = BeanIsNotAFactoryException.class)
public void rejectsFactoryGetOnNormalBean() {
	getBeanFactory().getBean("&rod");
}
 

/**
 * It should be illegal to dereference a normal bean as a factory.
 */
@Test(expected = BeanIsNotAFactoryException.class)
public void rejectsFactoryGetOnNormalBean() {
	getBeanFactory().getBean("&rod");
}
 

/**
 * It should be illegal to dereference a normal bean as a factory.
 */
@Test(expected = BeanIsNotAFactoryException.class)
public void rejectsFactoryGetOnNormalBean() {
	getBeanFactory().getBean("&rod");
}