【spring三级缓存】spring二级缓存put问题

问题遇到的现象和发生背景

【spring三级缓存】spring二级缓存只有一个put的地方，而且是在get才去put，那get一定是get不到的，那get存在的意义是什么？

问题相关代码，请勿粘贴截图

@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
    Object singletonObject = this.singletonObjects.get(beanName);
    if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
        synchronized (this.singletonObjects) {
            singletonObject = this.earlySingletonObjects.get(beanName);
            if (singletonObject == null && allowEarlyReference) {
                ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
                if (singletonFactory != null) {
                    singletonObject = singletonFactory.getObject();
                    this.earlySingletonObjects.put(beanName, singletonObject);
                    this.singletonFactories.remove(beanName);
                }
            }
        }
    }
    return singletonObject;
}

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

执行getSingleton，去单例缓存池中获取bean。

Object singletonObject = this.singletonObjects.get(beanName);

然后判断是否获取到，没获取到就去二级缓存中获取

if (singletonObject == null && isSingletonCurrentlyInCreation(beanName))
            singletonObject = this.earlySingletonObjects.get(beanName);

二级缓存中也没有获取到，就去三级缓存，实例工厂缓存中获取，allowEarlyReference是是否允许从实例工厂缓存中获取实例，默认true

if (singletonObject == null && allowEarlyReference) 
                ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);