如何在Java中实现可插拔适配器设计模式

问题描述

我知道如何实现基本的适配器设计模式，也知道C＃如何使用委托来实现可插拔适配器设计。但是我找不到用Java实现的任何东西。

I know how to implement basic Adapter design pattern and also knows how C# using delegation to implement Pluggable Adapter design. But I could not find anything implemented in Java. Would you mind pointing out an example code.

预先感谢。

推荐答案

可插拔适配器模式是一种用于创建适配器的技术，不需要为需要支持的每个适配器接口创建新类。

The pluggable adapter pattern is a technique for creating adapters that doesn't require making a new class for each adaptee interface you need to support.

在Java中，事情超级简单，但实际上并没有涉及您可能在C＃中使用的可插入适配器对象的对象。

In Java, this sort of thing is super easy, but there isn't any object involved that would actually correspond to the pluggable adapter object you might use in C#.

许多适配器目标接口都是功能接口-仅包含一种方法的接口。

Many adapter target interfaces are Functional Interfaces -- interfaces that contain just one method.

当您需要将此类接口的实例传递给客户端时，可以使用lambda函数或方法参考轻松地指定适配器。例如：

When you need to pass an instance of such an interface to a client, you can easily specify an adapter using a lambda function or method reference. For example:

interface IRequired
{
   String doWhatClientNeeds(int x);
}

class Client
{
   public void doTheThing(IRequired target);
}

class Adaptee
{
    public String adapteeMethod(int x);
}

class ClassThatNeedsAdapter
{
    private final Adaptee m_whatIHave;

    public String doThingWithClient(Client client)
    {
       // super easy lambda adapter implements IRequired.doWhatClientNeeds
       client.doTheThing(x -> m_whatIHave.adapteeMethod(x));
    }

    public String doOtherThingWithClient(Client client)
    {
       // method reference implements IRequired.doWhatClientNeeds
       client.doTheThing(this::_complexAdapterMethod);
    }

    private String _complexAdapterMethod(int x)
    {
        ...
    }
}

当目标接口具有多个方法时，我们使用匿名内部类：

When the target interface has more than one method, we use an anonymous inner class:

interface IRequired
{
   String clientNeed1(int x);
   int clientNeed2(String x);
}

class Client
{
   public void doTheThing(IRequired target);
}


class ClassThatNeedsAdapter
{
    private final Adaptee m_whatIHave;

    public String doThingWithClient(Client client)
    {
       IRequired adapter = new IRequired() {
           public String clientNeed1(int x) {
               return m_whatIHave.whatever(x);
           }
           public int clientNeed2(String x) {
               return m_whatIHave.whateverElse(x);
           }
       };
       return client.doTheThing(adapter);
    }
}

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