Question

也许这是一个简单的问题，但我仍然没有为它提供解决方案。我有这种类的配置：

abstract class SuperA {
   Resource a;
   Resource b;

   public SuperA() {
   }

   public SuperA(Resource a, Resource b) {
      this.a = a;
      this.b = b;
   }

   protected Resource getResourceA() {
       return a;
   }

   protected Resource getResourceB() {
       return b;
   }

}

class BaseA extends SuperA {
   public method1() {
       Resource myResource = getResourceA();
   }
}

class Manager {
   public Manager() {
      // I want to instantiate BaseA and inject some resources, but can't do
      // it through the constructor
      BaseA baseA = new BaseA(/*can't place parameters*/);
      // I could use Setters, but this would expose the Setters to BaseA too...
      baseA.setResourceA(new Resource());
      baseA.setResourceB(new Resource());
   }
}

在这种情况下，我想将资源注入Super类而不将任何Setter暴露给它的Base类而不继承构造函数，有没有办法做到这一点？

更新 - 澄清

BaseA类是API的扩展，我不希望其他用户有权修改实例化BaseA的核心引擎注入的资源。我希望BaseA 使用资源 NOT 来修改它们。

Answer 1

一个选项就是像这样的设定者，它是“包装可见的＆＃39;并且＆＃39; final＆＃39;

您在方法声明中使用final关键字来表示方法不能被子类覆盖。来自javadoc

然后你用＆＃39;包私人＆＃39;访问级别修饰符（不是精确的引用，但要解释）

（没有＆＃39;公共＆＃39;，＆＃39;私人＆＃39;，或＆＃39;受保护＆＃39;陈述）这意味着类本身可以在同一个包中看到/使用方法，类可以看到/使用该方法，但子类和世界不能看到/使用方法From javadoc

＆＃39;包私人＆＃39;单独可能会解决你的问题，但我会把＃final;＃39;只是为了使所需的行为更加明显，以便有助于未来的代码工作等。

例如：

abstract class SuperA {
   // making these private also helps
   // because it limits child classes to ONLY use getters
   // they can't even 'fiddle with' the raw values
   private Resource a;
   private Resource b;

   // would you want this public? perhaps also no 'access-modifier' 
   // the 'exact' specifics of a lot of this class would depend on your
   // specific use case (But I'd think you would want this package-only too most likely)
   public SuperA() {
   }

   // note no 'access-modifier', means package use only.
   SuperA(Resource a, Resource b) {
      this.a = a;
      this.b = b;
   }


   // can also have the same with setters
   // again no 'access-modifier' 
   final setResourceA(Resource a){ this.a = a;}
   final setResourceB(Resource b){ this.b = b;}

   public final Resource getResourceA() {
       return a;
   }


   public final Resource getResourceB() {
       return b;
   }

}

这将允许您的图书馆访问这些方法，但不允许子类或世界＆＃39;

Java - 在超类中注入资源而不暴露基类中的Setter

1 个答案: