这是什么样的Singleton？ [英] Which kind of Singleton is this?

问题描述

public class ConnectionManager {

    private static Map <String, ConnectionManager> managerInstances = new HashMap<String, ConnectionManager>();

    private String dsKey;
    private ConnectionManager(String dsKey){
        this.dsKey = dsKey;
    }

    public static ConnectionManager getInstance(String dsKey){
        ConnectionManager managerInstance = managerInstances.get(dsKey);

        if (managerInstance == null) {
            synchronized (ConnectionManager.class) {
                managerInstance = managerInstances.get(dsKey);
                if (managerInstance == null) {
                    managerInstance = new ConnectionManager(dsKey);
                    managerInstances.put(dsKey, managerInstance);
                }
            }
        }
        return managerInstance;
    }
}

我最近看到这个代码在Singleton模式是不按照GoF的书定义使用。 Singleton正在存储自己的实例的 Map 。

I recently saw this code somewhere where the Singleton pattern was not used as per book definition from GoF. Singleton is storing a Map of its own instances.

可以调用什么样的单例？或者这是Singleton的有效使用吗？

What kind of singleton can this be called? Or is this a valid use of Singleton?

推荐答案

这不是一个单身人士。它被称为 multiton pattern 。

It's not a singleton. It's called multiton pattern.

而不是每个应用程序使用单个实例 ，所以多重模式可以确保每个密钥的单个实例 。

Rather than have a single instance per application, the multiton pattern instead ensures a single instance per key.

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