如何多次实例化一个Singleton? [英] How to instantiate a Singleton multiple times?

问题描述

我的代码中需要一个单例.我用Java实现了它，并且效果很好.我这样做的原因是为了确保在多种环境中只有一个此类的实例.

I need a singleton in my code. I implemented it in Java and it works well. The reason I did it, is to ensure that in a mulitple environment, there is only one instance of this class.

但是现在我想使用单元测试在本地测试我的Singleton对象.因此，我需要模拟此Singleton的另一个实例(该对象可能来自另一个设备).那么是否有可能第二次实例化Singleton以进行测试，还是我必须对其进行模拟?

But now I want to test my Singleton object locally with a Unit test. For this reason I need to simulate another instance of this Singleton (the object that would be from another device). So is there a possiblity to instantiate a Singleton a second time for testing purpose or do I have to mock it?

我不确定，但是我认为可以通过使用其他类加载器来实现?

I'm not sure, but I think it could be possible by using a different class loader?

推荐答案

您可以使用反射调用单例类的私有构造函数，以创建该类的新实例.

You can invoke the private constructor of your singleton class using reflection to create a new instance of the class.

class MySingleton {
    private MySingleton() {
    }
}

class Test {
    public void test() throws Exception {
        Constructor<MySingleton> constructor = MySingleton.class.getConstructor();
        constructor.setAccessible(true);
        MySingleton otherSingleton = constructor.newInstance();
    }
}

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