Class Adapter概述

Class Adapter - 图1

玩具代码案例 - 电源插座

目标接口的调用者

Usa3PinSocket

当前插座只能使用IUsa3PinPlug接口，不支持IChina2PinPlug接口，我们的目标是让Usa3PinSocket的play方法同样能支持IChina2PinPlug接口。

  1. package online.javabook.gof.structural.patterns1.adapter.classadapter.plug.socket;
  3. import online.javabook.gof.structural.patterns1.adapter.classadapter.plug.api.IUsa3PinPlug;
  5. public class Usa3PinSocket {
  7.     public void play(IUsa3PinPlug usa3PinPlug) {
  8.         usa3PinPlug.runUsa3Pin();
  9.     }
  10. }

适配与被适配的类型

IChina2PinPlug

  1. package online.javabook.gof.structural.patterns1.adapter.classadapter.plug.api;
  3. public interface IChina2PinPlug {
  5.     public void runChina2Pin();
  6. }

China2PinPlug

  1. package online.javabook.gof.structural.patterns1.adapter.classadapter.plug.impl;
  3. import online.javabook.gof.structural.patterns1.adapter.classadapter.plug.api.IChina2PinPlug;
  5. public class China2PinPlug implements IChina2PinPlug {
  7.     @Override
  8.     public void runChina2Pin() {
  9.         System.out.println("I am china 2 pin plug, running");
  10.     }
  11. }

IUsa3PinPlug

  1. package online.javabook.gof.structural.patterns1.adapter.classadapter.plug.api;
  3. public interface IUsa3PinPlug {
  5.     public void runUsa3Pin();
  6. }

Usa3PinPlug

  1. package online.javabook.gof.structural.patterns1.adapter.classadapter.plug.impl;
  3. import online.javabook.gof.structural.patterns1.adapter.classadapter.plug.api.IUsa3PinPlug;
  5. public class Usa3PinPlug implements IUsa3PinPlug {
  7.     @Override
  8.     public void runUsa3Pin() {
  9.         System.out.println("I am usa 3 pin plug, running");
  10.     }
  11. }

类适配器类型

China2PinPlugToUsa3PinPlugAdapter

  1. package online.javabook.gof.structural.patterns1.adapter.classadapter.plug.adapter;
  3. import online.javabook.gof.structural.patterns1.adapter.classadapter.plug.api.IUsa3PinPlug;
  4. import online.javabook.gof.structural.patterns1.adapter.classadapter.plug.impl.China2PinPlug;
  6. public class China2PinPlugToUsa3PinPlugAdapter extends China2PinPlug implements IUsa3PinPlug {
  8.     @Override
  9.     public void runUsa3Pin() {
  10.         this.runChina2Pin();
  11.     }
  12. }

不基于类适配器模式的实现

重构目标接口的调用者

如果是第三方类我们可能不能修改这些代码

  1. package online.javabook.gof.structural.patterns1.adapter.classadapter.plug.app.bad;
  3. import online.javabook.gof.structural.patterns1.adapter.classadapter.plug.api.IChina2PinPlug;
  4. import online.javabook.gof.structural.patterns1.adapter.classadapter.plug.api.IUsa3PinPlug;
  6. public class RefactorUsa3PinSocket {
  8.     public void play(IUsa3PinPlug usa2PinPlug) {
  9.         usa2PinPlug.runUsa3Pin();
  10.     }
  12.     // add new api
  13.     public void play(IChina2PinPlug china2PinPlug) {
  14.         china2PinPlug.runChina2Pin();
  15.     }
  16. }

Main

  1. package org.gof.structural.patterns1.adapter.classadapter.app.bad;
  3. import org.gof.structural.patterns1.adapter.classadapter.plug.api.IChina2PinPlug;
  4. import org.gof.structural.patterns1.adapter.classadapter.plug.api.IUsa3PinPlug;
  5. import org.gof.structural.patterns1.adapter.classadapter.plug.impl.China2PinPlug;
  6. import org.gof.structural.patterns1.adapter.classadapter.plug.impl.Usa3PinPlug;
  7. import org.gof.structural.patterns1.adapter.classadapter.socket.Usa3PinSocket;
  9. public class Main {
  10.     public static void main(String[] args) {
  11.         // 当前实现需要破坏已有类型的实现，如果该类型是第三方库可能无法直接修改
  12.         RefactorUsa3PinSocket refactorUsa3PinSocket = new RefactorUsa3PinSocket();
  14.         IUsa3PinPlug usa3PinPlug = new Usa3PinPlug();
  15.         refactorUsa3PinSocket.play(usa3PinPlug);
  17.         // run on new api
  18.         IChina2PinPlug china2PinPlug = new China2PinPlug();
  19.         refactorUsa3PinSocket.play(china2PinPlug);
  20.     }
  21. }

基于类适配器模式的实现

Main

package org.gof.structural.patterns1.adapter.classadapter.app.good;

import org.gof.structural.patterns1.adapter.classadapter.plug.adapter.China2PinPlugToUsa3PinPlugAdapter;
import org.gof.structural.patterns1.adapter.classadapter.plug.api.IUsa3PinPlug;
import org.gof.structural.patterns1.adapter.classadapter.plug.impl.Usa3PinPlug;
import org.gof.structural.patterns1.adapter.classadapter.socket.Usa3PinSocket;

public class Main {
    public static void main(String[] args) {
        Usa3PinSocket usa3PinSocket = new Usa3PinSocket();

        IUsa3PinPlug usa3PinPlug = new Usa3PinPlug();
        usa3PinSocket.play(usa3PinPlug);

        // 使用类适配器
        IUsa3PinPlug adapter = new China2PinPlugToUsa3PinPlugAdapter();
        usa3PinSocket.play(adapter);
    }
}

Console

I am usa 2 pin plug, running
I am china 2 pin plug, running