问答平台（4），点赞

点赞

- 支持对帖子、评论点赞。
- 第1次点赞，第2次取消点赞。
- 点赞功能需要考虑性能的问题：点赞数据存到 Redis 里会提升性能。

首页点赞数量

- 统计帖子的点赞数量。

详情页点赞数量

- 统计点赞数量。
- 显示点赞状态。

---

工具类

• RedisKeyUtil：新增

  public class RedisKeyUtil {
  
      private static final String SPLIT = ":";
      private static final String PREFIX_ENTITY_LIKE = "like:entity";
  
      // 某个实体的赞
      // like:entity:entityType:entityId -> set(userId)
      public static String getEntityLikeKey(int entityType, int entityId) {
          return PREFIX_ENTITY_LIKE + SPLIT + entityType + SPLIT + entityId;
      }
  }

---

业务层

• LikeService：新增

  @Service
  public class LikeService {
  
      @Autowired
      private RedisTemplate redisTemplate;
  
      // 点赞
      public void like(int userId, int entityType, int entityId) {
          String entityLikeKey = RedisKeyUtil.getEntityLikeKey(entityType, entityId);
          boolean isMember = operations.opsForSet().isMember(entityLikeKey, userId);
  
          if (isMember) {
              operations.opsForSet().remove(entityLikeKey, userId);
          } else {
              operations.opsForSet().add(entityLikeKey, userId);
          }
      }
  
      // 查询某实体点赞的数量
      public long findEntityLikeCount(int entityType, int entityId) {
          String entityLikeKey = RedisKeyUtil.getEntityLikeKey(entityType, entityId);
          return redisTemplate.opsForSet().size(entityLikeKey);
      }
  
      // 查询某人对某实体的点赞状态
      public int findEntityLikeStatus(int userId, int entityType, int entityId) {
          String entityLikeKey = RedisKeyUtil.getEntityLikeKey(entityType, entityId);
          return redisTemplate.opsForSet().isMember(entityLikeKey, userId) ? 1 : 0;
      }
  }

---

表现层

• LikeController：新增

  @Controller
  public class LikeController implements CommunityConstant {
  
      @Autowired
      private LikeService likeService;
  
      @Autowired
      private HostHolder hostHolder;
  
      @RequestMapping(path = "/like", method = RequestMethod.POST)
      @ResponseBody
      public String like(int entityType, int entityId) {
          User user = hostHolder.getUser();
  
          // 点赞
          likeService.like(user.getId(), entityType, entityId);
          // 数量
          long likeCount = likeService.findEntityLikeCount(entityType, entityId);
          // 状态
          int likeStatus = likeService.findEntityLikeStatus(user.getId(), entityType, entityId);
          // 返回的结果
          Map<String, Object> map = new HashMap<>();
          map.put("likeCount", likeCount);
          map.put("likeStatus", likeStatus);
  
          return CommunityUtil.getJSONString(0, null, map);
      }
  }

• 实现首页的点赞数量的显示

  // HomeController -> getIndexPage(): 加入查找点赞数量的逻辑
  long likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_POST, post.getId());
  map.put("likeCount", likeCount);

• 实现帖子详情页（帖子、评论、回复）的点赞数量和点赞状态的显示

  // DiscussPostController -> getDiscussPost(): 加入如下逻辑
  
  // 点赞数量
  long likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_POST, discussPostId);
  model.addAttribute("likeCount", likeCount);
  // 点赞状态
  int likeStatus = hostHolder.getUser() == null ?
          0 : likeService.findEntityLikeStatus(hostHolder.getUser().getId(), ENTITY_TYPE_POST, discussPostId);
  model.addAttribute("likeStatus", likeStatus);
  
  // 评论VO列表
  // 点赞数量
  likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_COMMENT, comment.getId());
  commentVo.put("likeCount", likeCount);
  // 点赞状态
  likeStatus = hostHolder.getUser() == null ?
          0 : likeService.findEntityLikeStatus(hostHolder.getUser().getId(), ENTITY_TYPE_COMMENT, comment.getId());
  commentVo.put("likeStatus", likeStatus);
  
  // 回复VO列表            
  // 点赞数量
  likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_COMMENT, reply.getId());
  replyVo.put("likeCount", likeCount);
  // 点赞状态
  likeStatus = hostHolder.getUser() == null ?
          0 : likeService.findEntityLikeStatus(hostHolder.getUser().getId(), ENTITY_TYPE_COMMENT, reply.getId());
  replyVo.put("likeStatus", likeStatus);

---

页面

• discuss-detail.html

  <!-- 内容 -->
  <!-- 作者 -->
  <li class="d-inline ml-2">
      <a href="javascript:;" th:onclick="|like(this,1,${post.id});|" class="text-primary">
          <b th:text="${likeStatus==1?'已赞':'赞'}">赞</b> <i th:text="${likeCount}">11</i>
      </a>
  </li>
  <!-- 回帖列表 -->
  <li class="d-inline ml-2">
      <a href="javascript:;" th:onclick="|like(this,2,${cvo.comment.id});|" class="text-primary">
          <b th:text="${cvo.likeStatus==1?'已赞':'赞'}">赞</b> (<i th:text="${cvo.likeCount}">1</i>)
      </a>
  </li>
  <!-- 回复列表 -->
  <li class="d-inline ml-2">
      <a href="javascript:;" th:onclick="|like(this,2,${rvo.reply.id});|" class="text-primary">
          <b th:text="${rvo.likeStatus==1?'已赞':'赞'}">赞</b> (<i th:text="${rvo.likeCount}">1</i>)
      </a>
  </li>

• discuss.js

  function like(btn, entityType, entityId) {
      $.post(
          CONTEXT_PATH + "/like",
          {"entityType": entityType, "entityId": entityId},
          function (data) {
              data = $.parseJSON(data);
              if (data.code == 0) {
                  $(btn).children("i").text(data.likeCount);
                  $(btn).children("b").text(data.likeStatus == 1 ? '已赞' : '赞');
              } else {
                  alert(data.msg);
              }
          }
      );
  }

• index.html

  <!-- 帖子列表 -->
  <ul class="d-inline float-right">
      <li class="d-inline ml-2">赞 <span th:text="${map.likeCount}">11</span></li>
      <li class="d-inline ml-2">|</li>
      <li class="d-inline ml-2">回帖 <span th:text="${map.post.commentCount}">7</span></li>
  </ul>

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参考资料

• https://www.cnblogs.com/zyyweb/p/9637367.html