包装对静态方法/变量的访问的模式名称是什么？

Question

Following on from the question How do the Proxy, Decorator, Adapter, and Bridge Patterns differ? , how would you describe the following pattern which I've needed to implement on several occasions?

The scenario is that I'm referencing a static method or variable from a third-party class, but I want to hide it behind an interface so that I can mock it for testing.

For example, in Java the commons-lang library has a SystemUtils class with constants IS_OS_WINDOWS etc. I want to run tests which are independent of the underlying OS and mimic various OSs, so I wrap access to the constant as follows:

interface ISystemUtils {
    boolean isOsWindows();
}

class SystemUtilsImpl implements ISystemUtils {
    @Override
    public boolean isOsWindows() {
        return SystemUtils.IS_OS_WINDOWS;
    }
}

Is this a Proxy, a generic "wrapper", or something else?

Answer 1

This is called a Facade :

A facade is an object that provides a simplified interface to a larger body of code, such as a class library. A facade can:

• make a software library easier to use, understand and test, since the facade has convenient methods for common tasks;
• make the library more readable, for the same reason
• reduce dependencies of outside code on the inner workings of a library, since most code uses the facade, thus allowing more flexibility in developing the system
• wrap a poorly designed collection of APIs with a single well-designed API.

Answer 2

The Facade pattern is a good answer, although I do agree that it normally (in my experience at least) expose a number of different operations/classes. With that said, a number of other patterns can also serve the same purpose - Proxy would likely be my first choice, but Adaptor or Mediator could also be a good fit. Another term for this that you may also come across is a " delegate ".