如何动态创建实现某些接口的新类并实例化它? [英] How to dynamically create new class implementing some interface and instantiate it?

问题描述

是否可以在运行时用Java编写新的类?

Is it possible to compose new class at runtime in Java?

这意味着什么?便餐?编译器API?

What are the means for that? Refection? Compiler API?

我能做

package tests;

public class TryReflection02 {

    interface A {

    }

    public static void main(String[] args) {

        Object o = new A() {};

        System.out.println( o.toString() );

        o = A.class.newInstance() // exception

    }

}

我可以做具有 A.class 值的东西吗?

Can I do the same having A.class value?

推荐答案

不，您不能. A 是一个接口，只能实例化类.

No, you can't. A is an interface, and only classes can be instantiated.

您可以 做的是使用一个使用一些技巧的库/帮助程序来创建一个实现接口并实例化那个的类.JDK的 Proxy 类包含用于执行此操作的静态方法.对于与测试相关的用例，还有一些可以定制的工具可以做到: mockito ，例如.

What you can do is to use a library/helper that uses some trickery to create a class that implements the interface and instantiates that. The JDK's Proxy class contains static methods to do just that. There are also tools that can do it which are custom-geared for test-related use cases: mockito, for instance.

这些工具的作用恰恰是您在该问题的标题中所暗示的内容:它们不是实例化接口，而是生成一个实现该接口的新类，然后实例化该类.

These tools do exactly what you hint at in this question's title: rather than instantiating the interface, they generate a new class that implements the interface, and then instantiate that class.

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