mini-pms 33a

Observer 패턴 적용

01) App 클래스의 스태틱 멤버(필드와 메서드)를 인스턴트 멤버로 전환한다.

public class App {

  public static void main(String[] args) throws Exception {
    App01 app = new App01();
    app.service();
  }

  // 스태틱 멤버들이 공유하는 변수가 아니라면 로컬 변수로 만든다.
  public void service() throws Exception {
    List<Board> boardList = new ArrayList<>();
    File boardFile = new File("./board.json");

    List<Member> memberList = new LinkedList<>();
    File memberFile = new File("./member.json"); 

    List<Project> projectList = new LinkedList<>();
    File projectFile = new File("./project.json"); 

    List<Task> taskList = new ArrayList<>();
    File taskFile = new File("./task.json");

    loadObjects(boardList, boardFile, Board[].class);
    loadObjects(memberList, memberFile, Member[].class);
    loadObjects(projectList, projectFile, Project[].class);
    loadObjects(taskList, taskFile, Task[].class);

    Map<String,Command> commandMap = new HashMap<>();

    commandMap.put("/board/add", new BoardAddCommand(boardList));
    commandMap.put("/board/list", new BoardListCommand(boardList));
    commandMap.put("/board/detail", new BoardDetailCommand(boardList));
    commandMap.put("/board/update", new BoardUpdateCommand(boardList));
    commandMap.put("/board/delete", new BoardDeleteCommand(boardList));

    MemberListCommand memberListCommand = new MemberListCommand(memberList);
    commandMap.put("/member/add", new MemberAddCommand(memberList));
    commandMap.put("/member/list", memberListCommand);
    commandMap.put("/member/detail", new MemberDetailCommand(memberList));
    commandMap.put("/member/update", new MemberUpdateCommand(memberList));
    commandMap.put("/member/delete", new MemberDeleteCommand(memberList));

    commandMap.put("/project/add", new ProjectAddCommand(projectList, memberListCommand));
    commandMap.put("/project/list", new ProjectListCommand(projectList));
    commandMap.put("/project/detail", new ProjectDetailCommand(projectList));
    commandMap.put("/project/update", new ProjectUpdateCommand(projectList, memberListCommand));
    commandMap.put("/project/delete", new ProjectDeleteCommand(projectList));

    commandMap.put("/task/add", new TaskAddCommand(taskList, memberListCommand));
    commandMap.put("/task/list", new TaskListCommand(taskList));
    commandMap.put("/task/detail", new TaskDetailCommand(taskList));
    commandMap.put("/task/update", new TaskUpdateCommand(taskList, memberListCommand));
    commandMap.put("/task/delete", new TaskDeleteCommand(taskList));

    commandMap.put("/hello", new HelloCommand());

    Deque<String> commandStack = new ArrayDeque<>();
    Queue<String> commandQueue = new LinkedList<>();

    loop:
      while (true) {
        String inputStr = Prompt.inputString("명령> ");

        if (inputStr.length() == 0) {
          continue;
        }

        commandStack.push(inputStr);
        commandQueue.offer(inputStr);

        switch (inputStr) {
          case "history": printCommandHistory(commandStack.iterator()); break;
          case "history2": printCommandHistory(commandQueue.iterator()); break;
          case "quit":
          case "exit":
            System.out.println("안녕!");
            break loop;
          default:
            Command command = commandMap.get(inputStr);
            if (command != null) {
              try {
                command.execute();
              } catch (Exception e) {
                System.out.println("--------------------------------------------------------------");
                System.out.printf("명령어 실행 중 오류 발생: %s\n", e);
                System.out.println("--------------------------------------------------------------");
              }
            } else {
              System.out.println("실행할 수 없는 명령입니다.");
            }
        }
        System.out.println();
      }

    Prompt.close();

    saveObjects(boardList, boardFile);
    saveObjects(memberList, memberFile);
    saveObjects(projectList, projectFile);
    saveObjects(taskList, taskFile);
  }

  
  // 스태틱 멤버들이 공유하는 변수가 아니라면 로컬 변수로 만든다.
  void printCommandHistory(Iterator<String> iterator) {
    try {
      int count = 0;
      while (iterator.hasNext()) {
        System.out.println(iterator.next());
        count++;

        if ((count % 5) == 0 && Prompt.inputString(":").equalsIgnoreCase("q")) {
          break;
        }
      }
    } catch (Exception e) {
      System.out.println("history 명령 처리 중 오류 발생!");
    }
  }

  
  // 스태틱 멤버들이 공유하는 변수가 아니라면 로컬 변수로 만든다.
  private void saveObjects(Collection<?> list, File file) {
    BufferedWriter out = null;

    try {
      out = new BufferedWriter(new FileWriter(file));

      Gson gson = new Gson();
      String jsonStr = gson.toJson(list);
      out.write(jsonStr);

      out.flush();

      System.out.printf("총 %d 개의 객체를 '%s' 파일에 저장했습니다.\n",
          list.size(), file.getName());

    } catch (IOException e) {
      System.out.printf("객체를 '%s' 파일에  쓰는 중 오류 발생! - %s\n",
          file.getName(), e.getMessage());

    } finally {
      try {
        out.close();
      } catch (IOException e) {
      }
    }
  }

  
  // 스태틱 멤버들이 공유하는 변수가 아니라면 로컬 변수로 만든다.
  private <T> void loadObjects(
      Collection<T> list, // 객체를 담을 컬렉션
      File file, // JSON 문자열이 저장된 파일
      Class<T[]> clazz // JSON 문자열을 어떤 타입의 배열로 만들 것인지 알려주는 클래스 정보
      ) {
    BufferedReader in = null;

    try {
      in = new BufferedReader(new FileReader(file));
      list.addAll(Arrays.asList(new Gson().fromJson(in, clazz)));

      System.out.printf("'%s' 파일에서 총 %d 개의 객체를 로딩했습니다.\n",
          file.getName(), list.size());

    } catch (Exception e) {
      System.out.printf("'%s' 파일 읽기 중 오류 발생! - %s\n",
          file.getName(), e.getMessage());

    } finally {
      try {
        in.close();
      } catch (Exception e) {
      }
    }
  }
}

02) 애플리케이션을 시작하거나 종료할 때 실행할 옵저버의 메서드 호출 규칙을 정의한다.

• com.eomcs.context.ApplicationContextListener 생성

// 애플리케이션의 상태가 변경되었을 때 호출할 메서드 규칙을 정의한다.
// 즉 애플리케이션 상태 변경에 대해 보고를 받을 "Observer" 규칙을 정의한다.
// 보통 옵저버를 "리스너(listener)/구독자(subscriber)"라 부른다.

public interface ApplicationContextListener {
  // 발행자(애플리케이션)가 애플리케이션 시작을 알리기 위해 호출하는 메서드
  void contextInitialized();

  // 발행자(애플리케이션)가 애플리케이션 종료를 알리기 위해 호출하는 메서드
  void contextDestroyed();
}

03) 옵저버를 저장할 컬렉션 객체와 옵저버를 추가하고 제거하는 메서드를 추가한다.

public class App {

  // 옵저버를 보관할 컬렉션 객체
  List<ApplicationContextListener> listeners = new ArrayList<>();

  // 옵저버를 등록하는 메서드
  public void addApplicationContextListener(ApplicationContextListener listener) {
    listeners.add(listener);
  }

  // 옵저버를 제거하는 메서드
  public void removeApplicationContextListener(ApplicationContextListener listener) {
    listeners.remove(listener);
  }

  public static void main(String[] args) throws Exception {
    App app = new App();
    app.service();
  }
.
.
.
}

04) 애플리케이션의 service() 실행 전/후에 옵저버에게 통지하는 코드를 추가한다.

public class App {

  List<ApplicationContextListener> listeners = new ArrayList<>();

  public void addApplicationContextListener(ApplicationContextListener listener) {
    listeners.add(listener);
  }

  public void removeApplicationContextListener(ApplicationContextListener listener) {
    listeners.remove(listener);
  }

  // service() 실행 전에 옵저버에게 통지한다.
  private void notifyApplicationContextListenerOnServiceStarted() {
    // 곧 서비스를 시작할테니 준비하라고, 서비스 시작에 관심있는 각 옵저버에게 통지한다.
    for (ApplicationContextListener listener : listeners) {
      listener.contextInitialized();
    }
  }

  // service() 실행 후에 옵저버에게 통지한다.
  private void notifyApplicationContextListenerOnServiceStopped() {
    // 서비스가 종료되었으니 마무리 작업하라고, 마무리 작업에 관심있는 각 옵저버에게 통지한다.
    for (ApplicationContextListener listener : listeners) {
      listener.contextDestroyed();
    }
  }


  public static void main(String[] args) throws Exception {
    App app = new App();
    app.service();
  }

  public void service() throws Exception {

    // 옵저버에게 통지한다.
    notifyApplicationContextListenerOnServiceStarted();

    List<Board> boardList = new ArrayList<>();
    File boardFile = new File("./board.json"); 

    List<Member> memberList = new LinkedList<>();
    File memberFile = new File("./member.json"); 

    List<Project> projectList = new LinkedList<>();
    File projectFile = new File("./project.json"); 

    List<Task> taskList = new ArrayList<>();
    File taskFile = new File("./task.json"); 

    loadObjects(boardList, boardFile, Board[].class);
    loadObjects(memberList, memberFile, Member[].class);
    loadObjects(projectList, projectFile, Project[].class);
    loadObjects(taskList, taskFile, Task[].class);

    Map<String,Command> commandMap = new HashMap<>();

    commandMap.put("/board/add", new BoardAddCommand(boardList));
    commandMap.put("/board/list", new BoardListCommand(boardList));
    commandMap.put("/board/detail", new BoardDetailCommand(boardList));
    commandMap.put("/board/update", new BoardUpdateCommand(boardList));
    commandMap.put("/board/delete", new BoardDeleteCommand(boardList));

    MemberListCommand memberListCommand = new MemberListCommand(memberList);
    commandMap.put("/member/add", new MemberAddCommand(memberList));
    commandMap.put("/member/list", memberListCommand);
    commandMap.put("/member/detail", new MemberDetailCommand(memberList));
    commandMap.put("/member/update", new MemberUpdateCommand(memberList));
    commandMap.put("/member/delete", new MemberDeleteCommand(memberList));

    commandMap.put("/project/add", new ProjectAddCommand(projectList, memberListCommand));
    commandMap.put("/project/list", new ProjectListCommand(projectList));
    commandMap.put("/project/detail", new ProjectDetailCommand(projectList));
    commandMap.put("/project/update", new ProjectUpdateCommand(projectList, memberListCommand));
    commandMap.put("/project/delete", new ProjectDeleteCommand(projectList));

    commandMap.put("/task/add", new TaskAddCommand(taskList, memberListCommand));
    commandMap.put("/task/list", new TaskListCommand(taskList));
    commandMap.put("/task/detail", new TaskDetailCommand(taskList));
    commandMap.put("/task/update", new TaskUpdateCommand(taskList, memberListCommand));
    commandMap.put("/task/delete", new TaskDeleteCommand(taskList));

    commandMap.put("/hello", new HelloCommand());

    Deque<String> commandStack = new ArrayDeque<>();
    Queue<String> commandQueue = new LinkedList<>();

    loop:
      while (true) {
        String inputStr = Prompt.inputString("명령> ");

        if (inputStr.length() == 0) {
          continue;
        }

        commandStack.push(inputStr);
        commandQueue.offer(inputStr);

        switch (inputStr) {
          case "history": printCommandHistory(commandStack.iterator()); break;
          case "history2": printCommandHistory(commandQueue.iterator()); break;
          case "quit":
          case "exit":
            System.out.println("안녕!");
            break loop;
          default:
            Command command = commandMap.get(inputStr);
            if (command != null) {
              try {
                command.execute();
              } catch (Exception e) {
                System.out.println("--------------------------------------------------------------");
                System.out.printf("명령어 실행 중 오류 발생: %s\n", e);
                System.out.println("--------------------------------------------------------------");
              }
            } else {
              System.out.println("실행할 수 없는 명령입니다.");
            }
        }
        System.out.println();
      }

    Prompt.close();

    saveObjects(boardList, boardFile);
    saveObjects(memberList, memberFile);
    saveObjects(projectList, projectFile);
    saveObjects(taskList, taskFile);

    // 옵저버에게 통지한다.
    notifyApplicationContextListenerOnServiceStopped();
  }
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}

05) 애플리케이션을 시작하고 종료할 때 간단한 안내 메시지를 출력하는 옵저버를 추가한다.

• com.eomcs.pms.listener.AppInitListener 클래스 생성

public class AppInitListener implements ApplicationContextListener {
  @Override
  public void contextInitialized() {
    System.out.println("프로젝트 관리 시스템(PMS)에 오신 걸 환영합니다!");
  }

  @Override
  public void contextDestroyed() {
    System.out.println("프로젝트 관리 시스템(PMS)을 종료합니다!");
  }
}

• service() 호출 전에 옵저버를 등록한다.

  public class App04 {
  .
  .
  .
  public static void main(String[] args) throws Exception {
    App04 app = new App04();
  
    // 안내 메시지를 출력하는 옵저버 등록
    app.addApplicationContextListener(new AppInitListener());
  
    app.service();
  }
  .
  .
  .
  }