Java类成员变量

Question

I'm developing a research framework that needs to allow users to override core functionality.

I have a core class, called TorSocket, that has a method called createCircuit() which returns a TorCircuit class. I want users of the framework to be able to override TorCircuit functions without modifying the source but because the only way to create such a class is through TorSocket.createCircuit() I'm not sure how to.

I've tried as follows, in TorSocket, creating a member variable:

 public Class circuitClass;

and then users could do:

 sock.circuitClass = class MyCircuitClass extends TorCircuit { ...

and the TorSocket class would use circuitClass to instantiate.

However, I'm getting a syntax error using the above code, at "class." What is the correct syntax for this? I cant find much online although welcome pointers.

Finally, how to I then use TorSocket.circuitClass to instantiate?

Many thanks Gareth

Answer 1

Use

class MyCircuitClass extends TorCircuit {...}
sock.circuitClass = MyCircuitClass.class;

Answer 2

您不能让用户扩展您的基类，但仍然想自己控制对象的创建（您将如何精确地执行此操作？用户可以简单地调用new MyCircuitClass() ）-如果您想将对象的创建集中在内部我建议创建一个基类正在使用的接口集，用户必须提供具体的实现以通过工厂创建对象。

Answer 3

It seems a better way to do this is to use Generic methods like so:

public <T extends TorCircuit> T createCircuit(Class<T> torCircClass, boolean blocking) {
    T circ;
    try {
        circ = torCircClass.getDeclaredConstructor(TorSocket.class).newInstance(this);
    } catch (InstantiationException  | IllegalAccessException | NoSuchMethodException | InvocationTargetException e) {
        throw new RuntimeException(e);
    }
    circ. ...
    return circ;
}