07.适配器模式设计思想

// 类适配器: 基于继承
public interface ITarget {
    void f1();
    void f2();
    void f3();
}

public class Adaptee {
    public void fa() {
        //...
    }

    public void fb() {
        //...
    }

    public void fc() {
        //...
    }
}

public class Adaptor extends Adaptee implements ITarget {
    public void f1() {
        super.fa();
        System.out.println("调用适配器中方法");
    }

    public void f2() {
        //...重新实现f2()...
        super.fb();
        System.out.println("重新实现f2");
    }

    // 这里fc()不需要实现，直接继承自Adaptee，这是跟对象适配器最大的不同点
    @Override
    public void f3() {

    }
}

// 对象适配器：基于组合
public interface ITarget {
    void f1();

    void f2();

    void fc();
}

public class Adaptee {
    public void fa() { 
        //... 
    }

    public void fb() { 
        //...
    }

    public void fc() { 
        //... 
    }
}

public class Adaptor implements ITarget {

    private final Adaptee adaptee;

    public Adaptor(Adaptee adaptee) {
        this.adaptee = adaptee;
    }

    public void f1() {
        adaptee.fa(); //委托给Adaptee
    }

    public void f2() {
        //...重新实现f2()...
    }

    public void fc() {
        adaptee.fc();
    }
}

public interface SDCard {
    //从SD卡中读取数据
    String readSD();

    //往SD卡中写数据
    void writeSD(String msg);
}

//具体的SD卡
public class SDCardImpl implements SDCard {
    @Override
    public String readSD() {
        String msg = "SDCard read msg : SD";
        System.out.println(msg);
        return msg;
    }

    @Override
    public void writeSD(String msg) {
        System.out.println("SDCard write msg : " + msg);
    }
}

//计算机类
public class Computer {

    //从SD卡中读取数据
    public String readSD(SDCard sdCard) {
        if (sdCard == null) {
            throw new NullPointerException("sd card is null");
        }
        return sdCard.readSD();
    }
}

private void test1() {
    //计算机读SD卡
    Computer computer = new Computer();
    SDCardImpl sdCard = new SDCardImpl();
    computer.readSD(sdCard);
}

//输出结果是：
//SDCard read msg : SD

//适配者类的接口
public interface TFCard {
    //从TF卡中读取数据
    String readTF();
    //往TF卡中写数据
    void writeTF(String msg);
}

//适配者类
public class TFCardImpl implements TFCard {

    @Override
    public String readTF() {
        String msg = "TFCard read msg : TF";
        System.out.println(msg);
        return msg;
    }

    @Override
    public void writeTF(String msg) {
        System.out.println("TFCard write msg : " + msg);
    }
}

//适配器类
public class SDAdapterTF extends TFCardImpl implements SDCard {

    @Override
    public String readSD() {
        System.out.println("adapter read tf card");
        return readTF();
    }

    @Override
    public void writeSD(String msg) {
        System.out.println("adapter wrete tf card");
        writeTF(msg);
    }
}

private void test2() {
    //计算器适配，读卡器，去读TF卡中的内容
    Computer computer = new Computer();
    //创建适配器对象，完全没有影响之前计算机读SD卡的逻辑
    SDAdapterTF sdAdapterTF = new SDAdapterTF();
    computer.readSD(sdAdapterTF);
}

private void test1() {
    MediaPlayer mp3Player = new Mp3Player();
    mp3Player.play("mp3","file.mp3");
}

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

// Mp3Player.java
public class Mp3Player implements MediaPlayer {
    @Override
    public void play(String audioType, String fileName) {
        if (audioType.equalsIgnoreCase("mp3")) {
            System.out.println("Playing mp3 file. Name: " + fileName);
        } else {
            System.out.println("Invalid media. " + audioType + " format not supported");
        }
    }
}

private void test2() {
    AdvancedMediaPlayer vlcPlayer = new VlcPlayer();
    vlcPlayer.playVlc("vlc");
    AdvancedMediaPlayer mp4Player = new Mp4Player();
    mp4Player.playMp4("mp4");
}

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

// VlcPlayer.java
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) {
        // Do nothing
    }
}

// Mp4Player.java
public class Mp4Player implements AdvancedMediaPlayer {
    @Override
    public void playVlc(String fileName) {
        // Do nothing
    }

    @Override
    public void playMp4(String fileName) {
        System.out.println("Playing mp4 file. Name: " + fileName);
    }
}

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);
        }
    }
}

public class AudioPlayer implements MediaPlayer {
    MediaAdapter mediaAdapter;

    @Override
    public void play(String audioType, String fileName) {
        if (audioType.equalsIgnoreCase("mp3")) {
            System.out.println("Playing mp3 file. Name: " + fileName);
        } 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");
        }
    }
}

private void test3() {
    AudioPlayer audioPlayer = new AudioPlayer();
    audioPlayer.play("mp3", "mySong.mp3");
    audioPlayer.play("mp4", "video.mp4");
    audioPlayer.play("vlc", "movie.vlc");
    audioPlayer.play("avi", "doubi.avi");  // Not supported
}

public class CD { //这个类来自外部sdk，我们无权修改它的代码
  //...
  public static void staticFunction1() { //... }
  
  public void uglyNamingFunction2() { //... }

  public void tooManyParamsFunction3(int paramA, int paramB, ...) { //... }
  
   public void lowPerformanceFunction4() { //... }
}

// 使用适配器模式进行重构
public class ITarget {
  void function1();
  void function2();
  void fucntion3(ParamsWrapperDefinition paramsWrapper);
  void function4();
  //...
}
// 注意：适配器类的命名不一定非得末尾带Adaptor
public class CDAdaptor extends CD implements ITarget {
  //...
  public void function1() {
     super.staticFunction1();
  }
  
  public void function2() {
    super.uglyNamingFucntion2();
  }
  
  public void function3(ParamsWrapperDefinition paramsWrapper) {
     super.tooManyParamsFunction3(paramsWrapper.getParamA(), ...);
  }
  
  public void function4() {
    //...reimplement it...
  }
}

public class ASensitiveWordsFilter { // A敏感词过滤系统提供的接口
  //text是原始文本，函数输出用***替换敏感词之后的文本
  public String filterSexyWords(String text) {
    // ...
  }
  
  public String filterPoliticalWords(String text) {
    // ...
  } 
}

public class BSensitiveWordsFilter  { // B敏感词过滤系统提供的接口
  public String filter(String text) {
    //...
  }
}

public class CSensitiveWordsFilter { // C敏感词过滤系统提供的接口
  public String filter(String text, String mask) {
    //...
  }
}

// 未使用适配器模式之前的代码：代码的可测试性、扩展性不好
public class RiskManagement {
  private ASensitiveWordsFilter aFilter = new ASensitiveWordsFilter();
  private BSensitiveWordsFilter bFilter = new BSensitiveWordsFilter();
  private CSensitiveWordsFilter cFilter = new CSensitiveWordsFilter();
  
  public String filterSensitiveWords(String text) {
    String maskedText = aFilter.filterSexyWords(text);
    maskedText = aFilter.filterPoliticalWords(maskedText);
    maskedText = bFilter.filter(maskedText);
    maskedText = cFilter.filter(maskedText, "***");
    return maskedText;
  }
}

// 使用适配器模式进行改造
public interface ISensitiveWordsFilter { // 统一接口定义
  String filter(String text);
}

public class ASensitiveWordsFilterAdaptor implements ISensitiveWordsFilter {
  private ASensitiveWordsFilter aFilter;
  public String filter(String text) {
    String maskedText = aFilter.filterSexyWords(text);
    maskedText = aFilter.filterPoliticalWords(maskedText);
    return maskedText;
  }
}
//...省略BSensitiveWordsFilterAdaptor、CSensitiveWordsFilterAdaptor...

// 扩展性更好，更加符合开闭原则，如果添加一个新的敏感词过滤系统，
// 这个类完全不需要改动；而且基于接口而非实现编程，代码的可测试性更好。
public class RiskManagement { 
  private List<ISensitiveWordsFilter> filters = new ArrayList<>();
 
  public void addSensitiveWordsFilter(ISensitiveWordsFilter filter) {
    filters.add(filter);
  }
  
  public String filterSensitiveWords(String text) {
    String maskedText = text;
    for (ISensitiveWordsFilter filter : filters) {
      maskedText = filter.filter(maskedText);
    }
    return maskedText;
  }
}

// 外部系统A
public interface IA {
  //...
  void fa();
}
public class A implements IA {
  //...
  public void fa() { //... }
}
// 在我们的项目中，外部系统A的使用示例
public class Demo {
  private IA a;
  public Demo(IA a) {
    this.a = a;
  }
  //...
}
Demo d = new Demo(new A());

// 将外部系统A替换成外部系统B
public class BAdaptor implemnts IA {
  private B b;
  public BAdaptor(B b) {
    this.b= b;
  }
  public void fa() {
    //...
    b.fb();
  }
}
// 借助BAdaptor，Demo的代码中，调用IA接口的地方都无需改动，
// 只需要将BAdaptor如下注入到Demo即可。
Demo d = new Demo(new BAdaptor(new B()));

public class Collections {
  public static Emueration emumeration(final Collection c) {
    return new Enumeration() {
      Iterator i = c.iterator();
      
      public boolean hasMoreElments() {
        return i.hashNext();
      }
      
      public Object nextElement() {
        return i.next():
      }
    }
  }
}

List<String> stooges = Arrays.asList("Larry", "Moe", "Curly");

Vector v=new Vector();
for (Enumeration enum =v.elements(); enum.hasMoreElements();) {
  Object o = enum.nextElement();
  processObject(o);
}

List list=new ArrayList();
for(Iterator it=list.iterator();it.hasNext();){
   System.out.println(it.next());
}

public class NewEnumeration implements Enumeration {
    Iterator it;
  
    public NewEnumeration(Iterator it) {
        this.it = it;
    }
  
    public boolean hasMoreElements() {
        return it.hasNext();
    }
  
    public Object nextElement() {
        return it.next();
    }
  
    public static void main(String[] args) {
        List list = new ArrayList();
        list.add("a");
        list.add("b");
        list.add("C");
        for (Enumeration e = new NewEnumeration(list.iterator()); e.hasMoreElements(); ) {
            System.out.println(e.nextElement());
        }
    }
}

public interface Database {
    void connect();
    void query(String sql);
}

public class MySqlDatabase implements Database {
    @Override
    public void connect() {
        System.out.println("Connecting to MySQL Database");
    }

    @Override
    public void query(String sql) {
        System.out.println("Querying data from MySQL Database: " + sql);
    }
}

public class OracleDatabaseAdapter implements Database {
    private OracleDatabase oracleDatabase;

    public OracleDatabaseAdapter(OracleDatabase oracleDatabase) {
        this.oracleDatabase = oracleDatabase;
    }

    @Override
    public void connect() {
        oracleDatabase.open();
    }

    @Override
    public void query(String sql) {
        oracleDatabase.execute(sql);
    }
}

class OracleDatabase {
    void open() {
        System.out.println("Opening Oracle Database");
    }

    void execute(String sql) {
        System.out.println("Executing SQL on Oracle Database: " + sql);
    }
}

public interface Logger {
    void log(String message);
}

public class Log4jAdapter implements Logger {
    private org.apache.log4j.Logger logger;

    public Log4jAdapter(org.apache.log4j.Logger logger) {
        this.logger = logger;
    }

    @Override
    public void log(String message) {
        logger.info(message);
    }
}

public class SLF4JAdapter implements Logger {
    private org.slf4j.Logger logger;

    public SLF4JAdapter(org.slf4j.Logger logger) {
        this.logger = logger;
    }

    @Override
    public void log(String message) {
        logger.info(message);
    }
}