//类定义
public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {

/** Cache of singleton objects: bean name --> bean instance */

//生成的bean将存储在这个属性中。初始容量为256的Map对象。

private final Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(256);

/**

* Add the given singleton object to the singleton cache of this factory.

* <p>To be called for eager registration of singletons.

* @param beanName the name of the bean //

* @param singletonObject the singleton object

*/

protected void addSingleton(String beanName, Object singletonObject) {

        synchronized (this.singletonObjects) {

　　　　　　　//singletonObjects 是DefaultSingletonBeanRegistry类的一个Map类型的字段。把bean实例都添加到了Map对象中。

            this.singletonObjects.put(beanName, (singletonObject != null ? singletonObject : NULL_OBJECT));

            this.singletonFactories.remove(beanName);

            this.earlySingletonObjects.remove(beanName);

            this.registeredSingletons.add(beanName);

        }

    }