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。
  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。

Redis缓存用于点赞功能，可以提高性能。（面向Key编程）

1.建立RedisKeyUtil.java

package com.nowcoder.community.util;public class RedisKeyUtil {private static final String SPLIT = ":";private static final String PREFIX_ENTITY_LIKE = "like:entity";// 生成某个实体的赞// like:entity:entityType:entityId -> set(userId)，用id集合表示赞，不用整数，防止后面需求发生变化，集合中装载UserId,public static String getEntityLikeKey(int entityType, int entityId) {return PREFIX_ENTITY_LIKE + SPLIT + entityType + SPLIT + entityId;//拼的结果}}

2. 开发业务组件LikeService.java

package com.nowcoder.community.service;import com.nowcoder.community.util.RedisKeyUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Service;@Service
public class LikeService {@Autowiredprivate RedisTemplate redisTemplate;//注入Redis模板// 点赞public void like(int userId, int entityType, int entityId) {String entityLikeKey = RedisKeyUtil.getEntityLikeKey(entityType, entityId);boolean isMember = redisTemplate.opsForSet().isMember(entityLikeKey, userId);if (isMember) {//判断用户是否点过赞，用户id在集合中，就是点过赞。redisTemplate.opsForSet().remove(entityLikeKey, userId);} else {redisTemplate.opsForSet().add(entityLikeKey, userId);}}// 查询某实体被点赞的数量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;//返回整数，可以表现更多的状态，如踩等。1：点赞，0：没有点赞}
}

3. 表现层

异步请求，整个页面不刷新，更新点赞数就行

package com.nowcoder.community.controller;
import com.nowcoder.community.entity.User;
import com.nowcoder.community.service.LikeService;
import com.nowcoder.community.util.CommunityUtil;
import com.nowcoder.community.util.HostHolder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;import java.util.HashMap;
import java.util.Map;@Controller
public class LikeController {@Autowiredprivate LikeService likeService;@Autowiredprivate HostHolder hostHolder;@RequestMapping(path = "/like", method = RequestMethod.POST)//处理异步请求的方法@ResponseBodypublic 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：统一传递给页面Map map = new HashMap<>();map.put("likeCount", likeCount);map.put("likeStatus", likeStatus);return CommunityUtil.getJSONString(0, null, map);//返回Json格式的数据：正确返回0，提示，并将数据返回给页面}}

4.discuss-detail

点赞是在帖子详情页面进行的，也就是说要在该处，进行修改

赞 11
|
回帖 7

依赖的JS文件

function like(btn, entityType, entityId) {$.post(//POST请求，将点赞key拼接CONTEXT_PATH + "/like",{"entityType":entityType,"entityId":entityId},function(data) {//转存服务器返回的数据data = $.parseJSON(data);if(data.code == 0) {//判断请求是否成功$(btn).children("i").text(data.likeCount);//获取btn节点的子节点，改变它的内容。$(btn).children("b").text(data.likeStatus==1?'已赞':"赞");//赞成功了显示“已赞”。} else {alert(data.msg);//失败传出提示}});
}

5. 重启服务器，判断一下结果

注意变量要有“$”符号

5首页显示的点赞的数量要一致

在 HomeController.java中，将likeService注入
方法修改如下：

public String getIndexPage(Model model, Page page) {// 方法调用钱,SpringMVC会自动实例化Model和Page,并将Page注入Model.// 所以,在thymeleaf中可以直接访问Page对象中的数据.page.setRows(discussPostService.findDiscussPostRows(0));page.setPath("/index");List list = discussPostService.findDiscussPosts(0, page.getOffset(), page.getLimit());List> discussPosts = new ArrayList<>();if (list != null) {for (DiscussPost post : list) {Map map = new HashMap<>();map.put("post", post);User user = userService.findUserById(post.getUserId());map.put("user", user);long likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_POST, post.getId());map.put("likeCount", likeCount);discussPosts.add(map);}}model.addAttribute("discussPosts", discussPosts);return "/index";}

在index.html中找到首页显示赞的地方：

寒江雪 发布于 2019-04-15 15:32:18
赞 11
|
回帖 7

5帖子详情页面显示的点赞的数量和状态也要一致

DiscussPostController.java中将likeService注入，在方法内部进行处理

 public String getDiscussPost(@PathVariable("discussPostId") int discussPostId, Model model, Page page) {// 帖子DiscussPost post = discussPostService.findDiscussPostById(discussPostId);model.addAttribute("post", post);// 作者User user = userService.findUserById(post.getUserId());model.addAttribute("user", user);// 点赞数量long likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_POST, discussPostId);model.addAttribute("likeCount", likeCount);//将状态传到页面// 点赞状态int likeStatus = hostHolder.getUser() == null ? 0 :likeService.findEntityLikeStatus(hostHolder.getUser().getId(), ENTITY_TYPE_POST, discussPostId);//判断用户是否登录，没登录也可以看model.addAttribute("likeStatus", likeStatus);......

完整：

public String getDiscussPost(@PathVariable("discussPostId") int discussPostId, Model model, Page page) {// 帖子DiscussPost post = discussPostService.findDiscussPostById(discussPostId);model.addAttribute("post", post);// 作者User user = userService.findUserById(post.getUserId());model.addAttribute("user", user);// 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);// 评论分页信息page.setLimit(5);page.setPath("/discuss/detail/" + discussPostId);page.setRows(post.getCommentCount());// 评论: 给帖子的评论// 回复: 给评论的评论// 评论列表List commentList = commentService.findCommentsByEntity(ENTITY_TYPE_POST, post.getId(), page.getOffset(), page.getLimit());// 评论VO列表List> commentVoList = new ArrayList<>();if (commentList != null) {for (Comment comment : commentList) {// 评论VOMap commentVo = new HashMap<>();// 评论commentVo.put("comment", comment);// 作者commentVo.put("user", userService.findUserById(comment.getUserId()));// 点赞数量likeCount = likeService.findEntityLikeCount(ENTITY_TYPE_COMMENT, comment.getId());//评论的点赞状态，数量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);//装到VO中// 回复列表List replyList = commentService.findCommentsByEntity(ENTITY_TYPE_COMMENT, comment.getId(), 0, Integer.MAX_VALUE);// 回复VO列表List> replyVoList = new ArrayList<>();if (replyList != null) {for (Comment reply : replyList) {Map replyVo = new HashMap<>();// 回复replyVo.put("reply", reply);// 作者 replyVo.put("user", userService.findUserById(reply.getUserId()));// 回复目标User target = reply.getTargetId() == 0 ? null : userService.findUserById(reply.getTargetId());replyVo.put("target", target);// 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());//回复的处理也是类似的。replyVo.put("likeStatus", likeStatus);replyVoList.add(replyVo);}}commentVo.put("replys", replyVoList);// 回复数量int replyCount = commentService.findCommentCount(ENTITY_TYPE_COMMENT, comment.getId());commentVo.put("replyCount", replyCount);commentVoList.add(commentVo);}}model.addAttribute("comments", commentVoList);return "/site/discuss-detail";}}

6：帖子详情页面也要更改

另外两个位置处理方式相似