适配器模式

适配器模式

核心

1. 是有一个第三方的实现类，不能修改
2. 需要外部包一层，起名Adapter结尾，并实现相关的特定业务接口
3. 内部通过不能修改的第三方实现类去执行某些动作，完成业务功能
4. 相当于是面向对象思想里封装的应用实现

2个接口，普通播放器，高级播放器

普通播放器 MediaPlayer

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

高级播放器 AdvancedMediaPlayer

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

vlc播放器实现

public class VlcPlayer implements AdvancedMediaPlayer {
	public void playVlc(String fileName){
		System.out.println("vlc play :" + fileName);
	}
	public void playMp4(String fileName){
	
	}
}

mp4播放器实现

public class Mp4Player implements AdvancedMediaPlayer {
	public void playVlc(String fileName){
	
	}
	public void playMp4(String fileName){
		System.out.println("mp4 play:" + fileName);
	}
}

创建适配器，实现MediaPlayer

public MediaAdapter implements MediaPlayer {

	AdvancedMediaPlayer advancedMediaPlayer;
	public MediaAdapter(String audioType){
		switch(audioType){
			case "vlc":
				advancedMediaPlayer =  new VlcPlayer();
				break;
			case "mp4":
				advancedMediaPlayer =  new Mp4Player();
				break;
		}
	}
	
	public void play(String audioType, String fileName){
		switch(audioType){
			case "vlc":
				advancedMediaPlayer.playVlc(fileName);
				break;
			case "mp4":
				advancedMediaPlayer.playMp4(fileName);
				break;
		}
	}
}

引用适配器，进行定义开发

public AudioPlayer implements MediaPlayer {
	MediaAdapter mediaAdapter;
	public void play(String audioType, String fileName){
		switch(audioType){
			case "mp3":
				System.out.println("mp3 play:" + fileName);
				break;
			case "vlc":
				mediaAdapter = new  MediaAdapter("vlc");
				mediaAdapter.play(audioType,fileName);
				break;
			case "mp4":
				mediaAdapter = new  MediaAdapter("mp4");
				mediaAdapter.play(audioType,fileName);
				break;
		}
	}
}

main函数测试

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");
   }
}

适配器模式的代码样例

成员属性method和object对象，实例对象加方法，通过反射来进行执行

package com.jd.jmq.client.springboot.adaptor;

import com.jd.jmq.client.consumer.MessageListener;
import com.jd.jmq.common.message.Message;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;

public class MessageListenerReflectAdapter implements MessageListener {

    private final Method method;
    private final Object instance;

    public MessageListenerReflectAdapter(Object instance, Method method) {
        this.instance = instance;
        this.method = method;
        this.method.setAccessible(true);
    }

    @Override
    public void onMessage(List<Message> messages) {
        try {
            method.invoke(instance, messages);
        } catch (InvocationTargetException e) {
            if (e.getMessage() == null) {
                throw new RuntimeException(e.getCause());
            } else {
                throw new RuntimeException(e);
            }
        } catch (Exception e) {
            throw new RuntimeException("consume error", e);
        }
    }
}