Java实现问答点赞与回复功能详解

Question（问题）：

public class Question {
    private Long id;
    private String title;
    private String content;
    private Long userId;
    private List replies = new ArrayList<>();
    private int likeCount = 0;
    // getter 和 setter
}

Reply（回复）：

public class Reply {
    private Long id;
    private Long questionId;
    private Long userId;
    private String content;
    private int likeCount = 0;
    // getter 和 setter
}

Like（点赞记录）：用于防止重复点赞

public class Like {
    private Long id;
    private Long targetId;   // 目标ID（问题或回复）
    private String targetType; // 类型："question" 或 "reply"
    private Long userId;
    // getter 和 setter
}

@Service
public class LikeService {

    private Map> userLikes = new HashMap<>(); // 实际应使用数据库

    public boolean addLike(Long userId, String targetType, Long targetId) {
        String key = targetType + ":" + targetId;
        Set likedUsers = userLikes.computeIfAbsent(key, k -> new HashSet<>());

        if (likedUsers.contains(userId)) {
            return false; // 已点赞
        }

        likedUsers.add(userId);

        // 更新问题或回复的点赞数（实际中调用对应service）
        if ("question".equals(targetType)) {
            updateQuestionLikeCount(targetId, 1);
        } else if ("reply".equals(targetType)) {
            updateReplyLikeCount(targetId, 1);
        }
        return true;
    }

    private void updateQuestionLikeCount(Long questionId, int delta) {
        // 调用 QuestionService 增加点赞数
    }

    private void updateReplyLikeCount(Long replyId, int delta) {
        // 调用 ReplyService 增加点赞数
    }
}

@Service
public class ReplyService {

    private List replies = new ArrayList<>(); // 模拟存储

    public Reply createReply(Long questionId, Long userId, String content) {
        Reply reply = new Reply();
        reply.setId((long) (replies.size() + 1));
        reply.setQuestionId(questionId);
        reply.setUserId(userId);
        reply.setContent(content);
        replies.add(reply);
        return reply;
    }

    public List getRepliesByQuestionId(Long questionId) {
        return replies.stream()
                .filter(r -> r.getQuestionId().equals(questionId))
                .collect(Collectors.toList());
    }
}

@RestController
@RequestMapping("/api/questions")
public class QuestionController {

    @Autowired
    private ReplyService replyService;

    @Autowired
    private LikeService likeService;

    @PostMapping("/{id}/reply")
    public Reply replyToQuestion(
        @PathVariable Long id,
        @RequestParam Long userId,
        @RequestParam String content) {
        return replyService.createReply(id, userId, content);
    }

    @PostMapping("/{id}/like")
    public ResponseEntity likeQuestion(
        @PathVariable Long id,
        @RequestParam Long userId) {
        boolean success = likeService.addLike(userId, "question", id);
        if (success) {
            return ResponseEntity.ok("点赞成功");
        } else {
            return ResponseEntity.badRequest().body("已点赞");
        }
    }

    @PostMapping("/replies/{replyId}/like")
    public ResponseEntity likeReply(
        @PathVariable Long replyId,
        @RequestParam Long userId) {
        boolean success = likeService.addLike(userId, "reply", replyId);
        if (success) {
            return ResponseEntity.ok("点赞成功");
        } else {
            return ResponseEntity.badRequest().body("已点赞");
        }
    }
}