使用空方法的默认实现的设计模式 [英] Design pattern for default implementation with empty methods

问题描述

是否有特定的设计模式描述了提供非抽象默认实现的情况，该默认实现使用空的NO-OP实现在接口上实现所有或某些方法。这样做是为了减轻子类的负担，以实现自己可能不需要/使用的方法的负担：

Is there a specific design pattern that describes the scenario where a non-abstract default implementation is provided that implements all or some of the methods on the interface with empty, NO-OP implementations. This being done with the intent of alleviating subclasses with the burden of implementing methods that they themselves may not need/use:

public interface MyInterface {
    public void doThis();
    public void doThat();
    public void done();
}

public class MyClass implements MyInterface {
    public void doThis() {
        // NO-OP
    }
    public void doThat() {
        // NO-OP
    }
    public void done() {
        // Some standard implementation
    }
}

public class MuSubClass extends MyClass {
    public void doThat() {
        // Subclass only cares about doThat()
    }
}

我已经多次使用这种模式，包括 SAX框架中Java的DefaultHandler 和 MouseAdapter 。在某些情况下，此类被命名为Adaptors，但是我给人的印象是适配器模式在两个不同的接口之间转换。

I have seen this pattern used a number of times including Java's DefaultHandler in the SAX framework, and MouseAdapter. In somes cases such classes are named as Adaptors, but I was under the impression that the adapter pattern translates between two different interfaces.

鉴于在这些情况下，只有一个声明的接口正在转换为该接口的未定义子集-我不清楚这是如何实现的

Given that in these instances there is only one declared interface that is being translated to an undefined subset of that interface - I am not clear on how this is in the spirit of the adapter pattern.

此外，我还不太清楚它如何遵循 NullObject模式，考虑到某些方法可以实现，并且NullObject传统上是单例。

Furthermore, I don't quite see how this adheres to the NullObject pattern either, given that some methods could have an implementation, and the NullObject is traditionally a singleton.

推荐答案

没有默认实现的设计模式。

我通常会附加 DoNothing 类名的前缀。根据意图，我也使用 Base 或 Default （后者被广泛使用）。 MouseAdapter 可能应称为 DefaultMouseListener 。

I usually append DoNothing prefix to the name of class. Depending on it's intent I use also Base or Default (the latter is widely used). Probably MouseAdapter should be called DefaultMouseListener.

在您需要的情况下，可以使用简单的 DynamicProxy ，则您必须仅返回 nice默认值（ null（对象）， 0（数字）等）。

In the case you care, you can stub systematically an interface with a simple DynamicProxy, you must return only a "nice" default value (null for Object, 0 for numeric, etc).

顺便说一句，这是一个很好的问题。

BTW this is a very good question.

编辑

此外，它也不是 Stub 或< a href = http://en.wikipedia.org/wiki/Mock_object rel = nofollow noreferrer>模拟：也许可以将其与存根混淆，但意图有所不同。

Furthermore this is neither a Stub or a Mock: maybe it can be confused with a Stub but the intent is different.

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