2022-07-18-옵저버패턴-2부-패턴적용하기

01.옵저버패턴으로 적용

01.1 Subcriber

public interface Subscriber {

    void handleMessage(String message);
}

01.2 User

public class User implements Subscriber {

    private String name;

    public User(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    @Override
    public void handleMessage(String message) {
        System.out.println(message);
    }
}

01.3 ChatServer

• before

• import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  public class ChatServer {
  
      private Map<String, List<String>> messages;
  
      public ChatServer() {
          this.messages = new HashMap<>();
      }
  
  
      public void add(String subject, String message) {
          if (messages.containsKey(subject)) {
              messages.get(subject).add(message);
          } else {
              List<String> messageList = new ArrayList<>();
              messageList.add(message);
              messages.put(subject, messageList);
          }
      }
  
      public List<String> getMessage(String subject) {
          return messages.get(subject);
      }
  }

• after01.4 client
  • before

  • public class Client {
    
        public static void main(String[] args) {
            ChatServer chatServer = new ChatServer();
    
            User user1 = new User(chatServer);
            user1.sendMessage("디자인패턴", "이번엔 옵저버 패턴입니다.");
            user1.sendMessage("롤드컵2021", "LCK 화이팅!");
    
            User user2 = new User(chatServer);
            System.out.println(user2.getMessage("디자인패턴"));
    
            user1.sendMessage("디자인패턴", "예제 코드 보는 중..");
            System.out.println(user2.getMessage("디자인패턴"));
        }
    }

  • after

  • package me.whiteship.designpatterns._03_behavioral_patterns._19_observer._02_after;
    
    public class Client {
    
        public static void main(String[] args) {
            ChatServer chatServer = new ChatServer();
            User user1 = new User("keesun");
            User user2 = new User("whiteship");
    
            chatServer.register("오징어게임", user1);
            chatServer.register("오징어게임", user2);
    
            chatServer.register("디자인패턴", user1);
    
            chatServer.sendMessage(user1, "오징어게임", "아.. 이름이 기억났어.. 일남이야.. 오일남");
            chatServer.sendMessage(user2, "디자인패턴", "옵저버 패턴으로 만든 채팅");
    
            chatServer.unregister("디자인패턴", user2);
    
            chatServer.sendMessage(user2, "디자인패턴", "옵저버 패턴 장, 단점 보는 중");
        }
    }

• import java.lang.ref.WeakReference;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  public class ChatServer {
  
      private Map<String, List<Subscriber>> subscribers = new HashMap<>();
  
      public void register(String subject, Subscriber subscriber) {// 등록
          if (this.subscribers.containsKey(subject)) {
              this.subscribers.get(subject).add(subscriber);
          } else {
              List<Subscriber> list = new ArrayList<>();
              list.add(subscriber);
              this.subscribers.put(subject, list);
          }
      }
  
      public void unregister(String subject, Subscriber subscriber) {// 해지
          if (this.subscribers.containsKey(subject)) {
              this.subscribers.get(subject).remove(subscriber);
          }
      }
  
      public void sendMessage(User user, String subject, String message) {//상태변경 기능
          if (this.subscribers.containsKey(subject)) {
              String userMessage = user.getName() + ": " + message;
              this.subscribers.get(subject).forEach(s -> s.handleMessage(userMessage));
          }
      }
  }