一、适配器模式定义

别名： 门面模式
类型： 结构型模式
目的： 将不兼容的接口 通过适配器 转换成可兼容的接口。

二、例子

2.1 菜鸟教程例子

2.1.1 定义两个不兼容的播放接口MediaPlayer 、AdvancedMediaPlayer

public interface MediaPlayer {
   public void play(String audioType, String fileName);
}

public interface AdvancedMediaPlayer { 
   public void playVlc(String fileName);
   public void playMp4(String fileName);
}

2.1.2 定义AdvancedMediaPlayer两个实现类VlcPlayer 、Mp4Player

VlcPlayer

public class VlcPlayer implements AdvancedMediaPlayer{
   @Override
   public void playVlc(String fileName) {
      System.out.println("Playing vlc file. Name: "+ fileName);      
   }
   @Override
   public void playMp4(String fileName) {//什么也不做}
}

Mp4Player

public class Mp4Player implements AdvancedMediaPlayer{
 
   @Override
   public void playVlc(String fileName) { //什么也不做 }
 
   @Override
   public void playMp4(String fileName) {
      System.out.println("Playing mp4 file. Name: "+ fileName);      
   }
}

2.1.3 定义适配器MediaAdapter

将AdvancedMediaPlayer 接口适配MediaPlayer 接口

public class MediaAdapter implements MediaPlayer {
 
   AdvancedMediaPlayer advancedMusicPlayer;
 
   public MediaAdapter(String audioType){
      if(audioType.equalsIgnoreCase("vlc") ){
         advancedMusicPlayer = new VlcPlayer();       
      } else if (audioType.equalsIgnoreCase("mp4")){
         advancedMusicPlayer = new Mp4Player();
      }  
   }
 
   @Override
   public void play(String audioType, String fileName) {
      if(audioType.equalsIgnoreCase("vlc")){
         advancedMusicPlayer.playVlc(fileName);
      }else if(audioType.equalsIgnoreCase("mp4")){
         advancedMusicPlayer.playMp4(fileName);
      }
   }
}

2.1.4 定义AudioPlayer 并使用MediaAdapter

public class AudioPlayer implements MediaPlayer {
   MediaAdapter mediaAdapter; 
 
   @Override
   public void play(String audioType, String fileName) {    
 
      //播放 mp3 音乐文件的内置支持
      if(audioType.equalsIgnoreCase("mp3")){
         System.out.println("Playing mp3 file. Name: "+ fileName);         
      } 
      //mediaAdapter 提供了播放其他文件格式的支持
      else if(audioType.equalsIgnoreCase("vlc")|| audioType.equalsIgnoreCase("mp4")){
         mediaAdapter = new MediaAdapter(audioType);
         mediaAdapter.play(audioType, fileName);
      }
      else{
         System.out.println("Invalid media. "+  audioType + " format not supported");
      }
   }   
}

2.1.5 使用

public class AdapterPatternDemo {
   public static void main(String[] args) {
      AudioPlayer audioPlayer = new AudioPlayer();
 
      audioPlayer.play("mp3", "beyond the horizon.mp3");
      audioPlayer.play("mp4", "alone.mp4");
      audioPlayer.play("vlc", "far far away.vlc");
      audioPlayer.play("avi", "mind me.avi");
   }
}

2.2 JDK源码——InputStreamReader

InputStream接口适配Reader接口

public abstract class Reader implements Readable, Closeable {
    public int read(CharBuffer target) throws IOException {
        if (target.isReadOnly())
            throw new ReadOnlyBufferException();

        int nread;
        if (target.hasArray()) {
            char[] cbuf = target.array();
            int pos = target.position();
            int rem = Math.max(target.limit() - pos, 0);
            int off = target.arrayOffset() + pos;
            nread = this.read(cbuf, off, rem);
            if (nread > 0)
                target.position(pos + nread);
        } else {
            int len = target.remaining();
            char[] cbuf = new char[len];
            nread = read(cbuf, 0, len);
            if (nread > 0)
                target.put(cbuf, 0, nread);
        }
        return nread;
    }

}

public class InputStreamReader extends Reader {
	private final StreamDecoder sd;
	
    public InputStreamReader(InputStream in) {
        super(in);
        Charset cs = Charset.defaultCharset();
        sd = StreamDecoder.forInputStreamReader(in, lockFor(this), cs);
    }
	public int read(CharBuffer target) throws IOException {
        return sd.read(target);
    }
}

2.3 Spring源码——AdvisorAdapter

切面适配器接口。

Advisor适配MethodInterceptor 接口

public interface AdvisorAdapter {
    boolean supportsAdvice(Advice advice);

    MethodInterceptor getInterceptor(Advisor advisor);
}

实现类MethodBeforeAdviceAdapter

class MethodBeforeAdviceAdapter implements AdvisorAdapter, Serializable {
    MethodBeforeAdviceAdapter() {
    }

    public boolean supportsAdvice(Advice advice) {
        return advice instanceof MethodBeforeAdvice;
    }

    public MethodInterceptor getInterceptor(Advisor advisor) {
        MethodBeforeAdvice advice = (MethodBeforeAdvice)advisor.getAdvice();
        return new MethodBeforeAdviceInterceptor(advice);
    }
}

---

三、其他设计模式

创建型模式
结构型模式

• 1、设计模式——装饰器模式（Decorator Pattern）+ Spring相关源码

行为型模式

• 1、设计模式——访问者模式（Visitor Pattern）+ Spring相关源码
• 2、设计模式——中介者模式（Mediator Pattern）+ JDK相关源码
• 3、设计模式——策略模式（Strategy Pattern）+ Spring相关源码
• 4、设计模式——状态模式（State Pattern）
• 5、设计模式——命令模式（Command Pattern）+ Spring相关源码
• 6、设计模式——观察者模式（Observer Pattern）+ Spring相关源码
• 7、设计模式——备忘录模式（Memento Pattern）
• 8、设计模式——模板方法模式（Template Pattern）+ Spring相关源码
• 9、设计模式——迭代器模式（Iterator Pattern）+ Spring相关源码
• 10、设计模式——责任链模式（Chain of Responsibility Pattern）+ Spring相关源码
• 11、设计模式——解释器模式（Interpreter Pattern）+ Spring相关源码