指定在命令行参数中使用的Java接口实现 [英] Specify which implementation of Java interface to use in command line argument

问题描述

假设我有一个Java接口 Blender.java ，包含各种实现 Cuisinart.java ， Oster.java ， Blendtec.java 等等。现在我想写一个这样的程序：

Say I have a Java interface Blender.java with various implementations Cuisinart.java, Oster.java, Blendtec.java, etc. Now I want to write a program like so:

public class Blendifier {
    // ...
    public static void main(String... args) {
        Blender blender = new Cuisinart();
        blender.blend();
    }
}

但现在如果我想使用 Blendtec 而不是 Cuisinart ，我必须打开源代码，更改代码并重新编译。

But now if I want to use the Blendtec instead of the Cuisinart, I have to open up the source, change the code, and recompile.

相反，我希望能够通过编写课程来指定在运行程序时动态使用哪个 Blender 我希望将name作为命令行参数。

Instead, I'd like to be able to specify which Blender to use on the fly when I run the program, by writing the class name I want as a command line argument.

但是如何从包含类的 name 的String转到构建实际的那个类的实例？

But how can I go from a String containing the name of a class, to constructing an actual instance of that class?

推荐答案

如果你不想经历麻烦那就是Java反射，你可以编写一个简单的静态工厂方法，它接受一个String并返回相应的对象。

If you don't want to go through the trouble that is Java reflection, you can write a simple static factory method that takes a String and returns the appropriate object.

public static Blender createBlender(String type){
    switch(type){
    case "Cuisinart": return new Cuisinart();
    case "Oster": return new Oster();
    //etc
    }
}

然后你就过去了在你的命令行参数中，你将拥有你需要的任何Blender。

Then you just pass in your command line argument into it and you'll have whatever Blender you need.

唯一可能的设计问题是你必须为每个类输入一行它实现了Blender，因此如果稍后添加更多类型，则必须更新该方法。

The only possible design issue is that you would have to type out a line for every class that implements Blender, so you'd have to update the method if you added more types later.

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