1、点赞

需求

点赞

• 支持对帖子、评论点赞
• 第一次点赞，第二次取消点赞

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

实现

1、新建个工具类，用来生成redis key的

public class RedisKeyUtil {

    private static final String SPLIT = ":";
    private static final String PREFIX_ENTITY_LIKE = "like:entity";

    /**
     * 某个实体的赞
     * 包含实体类型和实体ID信息
     * 格式：like:entity:entityType:entityId
     */
    public static String getEntityLikeKey(int entityType, int entityId) {
        return PREFIX_ENTITY_LIKE + SPLIT + entityType + SPLIT + entityId;
    }
}

2、实现点赞业务，新建likeService，实现like方法

@Service
public class LikeService {

    @Autowired
    private RedisTemplate redisTemplate;

    //点赞
    public void like(int userId, int entityType, int entityId, int entityUserId) {
        String entityLikeKey = RedisKeyUtil.getEntityLikeKey(entityType, entityId);
        Boolean isMember = redisTemplate.opsForSet().isMember(entityLikeKeykey, userId);
        if (isMember) {
            redisTemplate.opsForSet().remove(entityLikeKeykey, userId);
        } else {
            redisTemplate.opsForSet().add(entityLikeKeykey, 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;
    }

3、完成controller层，向前台返回json数据
当点赞触发时，向数据库中新增，并且返回查询到的点赞数、点赞状态，并以json返回

@Controller
public class LikeController implements CommunityConstant {

    @Autowired
    private LikeService likeService;

    @Autowired
    private HostHolder hostHolder;

    @Autowired
    private RedisTemplate redisTemplate;

    @RequestMapping(value = "/like", method = RequestMethod.POST)
    @ResponseBody
    public String like(int entityType, int entityId,int entityUserId,int postId) {
        User user = hostHolder.getUser();
        //点赞
        likeService.like(user.getId(), entityType, entityId,entityUserId);
        //数量
        long entityLikeCount = likeService.findEntityLikeCount(entityType, entityId);
        //状态
        int entityLikeStatus = user == null ? 0 : likeService.findEntityLikeStatus(user.getId(), entityType, entityId);

        Map<String, Object> map = new HashMap<>();
        map.put("likeCount", entityLikeCount);
        map.put("likeStatus", entityLikeStatus);

        return CommunityUtil.getJSONString(0, null, map);
    }
}

4、前台完成相应的显示
当单击“点赞”时，触发js，后端返回数据，前端响应
html

<ul class="d-inline float-right">
    <li class="d-inline ml-2">
         <a href="javascript:;" th:onclick="|like(this,1,${post.id},${post.userId},${post.id});|" class="text-primary">
            <b th:text="${likeStatus==1?'已赞':'赞'}">赞</b>
            <i th:text="${likeCount}">11</i></a>
    </li>
    <li class="d-inline ml-2">|</li>
    <li class="d-inline ml-2"><a href="#replyform" class="text-primary">回帖 <i th:text="${post.commentCount}">7</i></a></li>
</ul>

function like(btn, entityType, entityId, entityUserId,postId) {
    $.post(
        CONTEXT_PATH + "/like",
        {"entityType": entityType, "entityId": entityId,"entityUserId":entityUserId,"postId":postId},
        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);
            }


        }
    );
}