如果我想在服务层使用此DTO，如何将实体继承表示为DTO

public class User {
    private Long id;
    private String name;
    private String email;
    private String password;

    // Getters and Setters
}

public class UserDTO extends User {
    // 可以添加额外的DTO特定属性
    private String additionalInfo;

    // Getters and Setters
}

public class UserService {
    public UserDTO getUserById(Long id) {
        // 假设从数据库获取User实体
        User user = userRepository.findById(id).orElseThrow(() -> new EntityNotFoundException("User not found"));

        // 将User实体转换为UserDTO
        UserDTO userDTO = new UserDTO();
        userDTO.setId(user.getId());
        userDTO.setName(user.getName());
        userDTO.setEmail(user.getEmail());
        userDTO.setAdditionalInfo("Some additional info");

        return userDTO;
    }
}

public class UserDTO {
    private Long id;
    private String name;
    private String email;

    @JsonIgnore
    private User friend; // 忽略这个引用

    // Getters and Setters
}

public class UserDTO {
    private Long id;
    private String name;
    private String email;

    // Getters and Setters
}