在Java中实现接口时降低可见性 [英] Reduce visibility when implementing interface in Java

问题描述

我想设计类A实现接口C并降低方法的可见性（在C中声明）以使其从外部世界安全，使得在A类中实现的接口中的一个方法成为私有的（降低了可见性） A）级。出于安全原因，我必须这样做，我该怎么做，是否有解决方法。我们知道默认情况下，界面有公共成员。但我没有选择，有人可以帮助我。提前致谢。

I would like to design class A implements interface C and reduce the visibility of a method (declared in C)to make it secure from outer world, make one of the methods in interface implemented in class A as private (reducing visibility in class A). I have to do this for security reason, how can I do this, is there a workaround. We do know that by default, the interface has public members. But there is no option for me, can someone help me. Thanks in advance.

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因此，没有办法从接口获得类实现方法并将其设为私有。并且所有实现任何接口方法的类都将始终具有公共方法？

-- So , there is no way, to have a class implement method from interface and make it private. And all classes that implement any interface's method will always have public methods?

推荐答案

不，您无法降低其可见性接口中的方法。如果有人写道，你会发生什么：

No, you can't reduce the visibility of a method in an interface. What would you expect to happen if someone wrote:

C foo = new A();
foo.methodDeclaredPrivateInA();

？就编译器而言，所有引用 C 实现的内容都有权调用其中的任何方法 - 这就是Liskov的替换原则。

? As far as the compiler is concerned, everything with a reference to an implementation of C has the right to call any methods within it - that's what Liskov's Substitution Principle is all about.

如果你不想实现整个公共接口，不要实现它 - 或者如果你绝对必须抛出异常。

If you don't want to implement the whole of a public interface, don't implement it - or throw exceptions if you absolutely must.

还值得注意的是，源代码中提供的可访问性很少是一个很好的安全性度量。如果您的类在VM中运行，而VM又可以确定自己的权限，那么任何人都可以通过反射使成员可见。

It's also worth noting that the accessibility provided in source code is rarely a good security measure. If your class is running in a VM which in turn gets to determine its own permissions, anyone can make members visible via reflection.

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