最后的回调

// bean 创建后的回调
// Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
    Object singletonInstance = getSingleton(beanName);
    if (singletonInstance instanceof SmartInitializingSingleton) {
        SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
        if (System.getSecurityManager() != null) {
            AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
                smartSingleton.afterSingletonsInstantiated();
                return null;
            }, getAccessControlContext());
        }
        else {
            smartSingleton.afterSingletonsInstantiated();
        }
    }
}