一分钟理解DAO和Repository

public interface Dao<T> {
    Optional<T> get(long id);    
    List<T> getAll();    
    void save(T t);  
    void update(T t, String[] params);    
    void delete(T t);
}
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public class UserDao implements Dao<User> {
    private List<User> users = new ArrayList<>();
    
    public UserDao() {
        users.add(new User("John", "john@domain.com"));
        users.add(new User("Susan", "susan@domain.com"));
    }
    
    @Override
    public Optional<User> get(long id) {
        return Optional.ofNullable(users.get((int) id));
    }
    
    @Override
    public List<User> getAll() {
        return users;
    }
    
    @Override
    public void save(User user) {
        users.add(user);
    }
    
    // ...
}
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public interface UserRepository {
    User get(Long id);
    void add(User user);
    void update(User user);
    void remove(User user);
}
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public class UserRepositoryImpl implements UserRepository {
    private UserDaoImpl userDaoImpl;
    
    @Override
    public User get(Long id) {
        User user = userDaoImpl.read(id);
        return user;
    }


    @Override
    public void add(User user) {
        userDaoImpl.create(user);
    }


    // ...
}
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