Spring三级缓存

public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {
        //1级缓存 用于存放 已经属性赋值 初始化后的 单列BEAN
        private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
        //2级缓存 用于存在已经实例化，还未做代理属性赋值操作的 单例
        private final Map<String, Object> earlySingletonObjects = new HashMap<>(16);
        //3级缓存 存储单例BEAN的工厂
        private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);
        //已经注册的单例池里的beanName
        private final Set<String> registeredSingletons = new LinkedHashSet<>(256);
        //正在创建中的beanName
        private final Set<String> singletonsCurrentlyInCreation =
                Collections.newSetFromMap(new ConcurrentHashMap<>(16));
        //缓存查找bean  如果1级没有，从2级获取,也没有,从3级创建放入2级
        protected Object getSingleton(String beanName, boolean allowEarlyReference) {
            Object singletonObject = this.singletonObjects.get(beanName); //1级
            if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
                synchronized (this.singletonObjects) {
                    singletonObject = this.earlySingletonObjects.get(beanName); //2级
                    if (singletonObject == null && allowEarlyReference) {
                        //3级缓存  在doCreateBean中创建了bean的实例后，封装ObjectFactory放入缓存的
                        ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
                        if (singletonFactory != null) {
                            //创建未赋值的bean
                            singletonObject = singletonFactory.getObject();
                            //放入到二级缓存
                            this.earlySingletonObjects.put(beanName, singletonObject);
                            //从三级缓存删除
                            this.singletonFactories.remove(beanName);
                        }
                    }
                }
            }
            return singletonObject;
        }   
    }

protected void addSingleton(String beanName, Object singletonObject) {
            synchronized (this.singletonObjects) {
                //放入一级缓存
                this.singletonObjects.put(beanName, singletonObject);
                //从三级缓存删除
                this.singletonFactories.remove(beanName);
                //从二级缓存删除
                this.earlySingletonObjects.remove(beanName);
                this.registeredSingletons.add(beanName);
            }
        }

protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
            synchronized (this.singletonObjects) {
                if (!this.singletonObjects.containsKey(beanName)) {
                    //一级缓存没有，放入三级缓存
                    this.singletonFactories.put(beanName, singletonFactory);
                    //从二级缓存删除，确保二级缓存没有该bean
                    this.earlySingletonObjects.remove(beanName);
                    this.registeredSingletons.add(beanName);
                }
            }
        }

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
    BeanWrapper instanceWrapper = null;
    
    if (instanceWrapper == null) {
        //实例化对象
        instanceWrapper = this.createBeanInstance(beanName, mbd, args);
    }

    final Object bean = instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null;
    Class<?> beanType = instanceWrapper != null ? instanceWrapper.getWrappedClass() : null;
   
    //判断是否允许提前暴露对象，如果允许，则直接添加一个 ObjectFactory 到三级缓存
    boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
                isSingletonCurrentlyInCreation(beanName));
    if (earlySingletonExposure) {
        //添加三级缓存
        addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
    }

    //填充属性
    this.populateBean(beanName, mbd, instanceWrapper);
    //执行初始化方法，并创建代理
    exposedObject = initializeBean(beanName, exposedObject, mbd);
    return exposedObject;
}

protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) {
    Object exposedObject = bean;
    if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
        for (BeanPostProcessor bp : getBeanPostProcessors()) {
            if (bp instanceof SmartInstantiationAwareBeanPostProcessor) {
                SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp;
                // 如果需要代理，这里会返回代理对象；否则返回原始对象
                exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);
            }
        }
    }
    return exposedObject;
}

public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport
        implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {
    @Override
    public Object getEarlyBeanReference(Object bean, String beanName) {
        Object cacheKey = getCacheKey(bean.getClass(), beanName);
        // 记录已被代理的对象
        this.earlyProxyReferences.put(cacheKey, bean);
        return wrapIfNecessary(bean, beanName, cacheKey);
    }
}

//缓存查找bean  如果1级没有，从2级获取,也没有,从3级创建放入2级
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
    Object singletonObject = this.singletonObjects.get(beanName); //1级
    if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
        synchronized (this.singletonObjects) {
            singletonObject = this.earlySingletonObjects.get(beanName); //2级
            if (singletonObject == null && allowEarlyReference) {
                //3级缓存  在doCreateBean中创建了bean的实例后，封装ObjectFactory放入缓存的
                ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
                if (singletonFactory != null) {
                    //创建未赋值的bean
                    singletonObject = singletonFactory.getObject();
                    //放入到二级缓存
                    this.earlySingletonObjects.put(beanName, singletonObject);
                    //从三级缓存删除
                    this.singletonFactories.remove(beanName);
                }
            }
        }
    }
    return singletonObject;
}