Question

i m just learning java, and i meet some problems. Here we have simple factory pattern:

public class SomeFactory {
    ...
     public static void registerProduct(String name, Class<? extends IProduct > f)
}

public SomeProduct implements IProduct {
   static {
       SomeFactory.register("some product", SomeProduct.class);
   }
   ...
}

All products should register themselves at factory.

But before using this code, all Products classes should be loaded. I can put Class.forName() somewhere, for example in main function. But i want to avoid such sort of manual classes loading. I want just add new IProduct implementations, without updating other parts(such as SomeFactory or Main methods, etc.). But i wonder, is it possible to automatically load some classes(marked with annotation, for example)?

P.S 我想指出,在运行时间,所有<代码>不会增加其他班级。汇编之前,先了解《电子格式实施情况。

UPD#1 Thank for your answering! But is it possible to make auto-generated property-file with IProduct instances? I mean is it possible to make some build-time script(for maven for example) that generates property-file or loader code? Are there such solutions or frameworks?

UPD#2 I finished with using Reflections library that provides run-time information, by scanning classpath at startup.

Answer 1

这是可能的,但并非易事。需要扫描所有班级,看它们是否有通知或执行<代码>。 IProduct接口。见。如何在 Java找到特定类别的所有子类别?

我确实会把它简单地保留下来,而且只是有一个装上工厂本身或外部档案(例如,Properties文档)的班级清单。

Answer 2

Have each product register itself, using a static block like this:

 class MyProduct1{

     static{
         SomeFactory.register(MyProduct1.getClass());
     }
     ..
     ..
 }

外部财产档案可以追踪所有产品。
您的主要方法可以把这一产品清单归为一等。

这样,你就迫切需要制定任何具体产品,而财产档案却在不断变化。 Ah! 是否增加安全登记也将是一个加点。

注:我只是提出一个想法,我发明试图自己:

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