07.利用Redis实现点赞排行榜功能

学习目标：

提示：学习如何利用Redisson实现点赞排行榜功能，按照时间顺序
当用户给某一篇文章点赞后，会再数据库中存储一条数据，并且在Redis中存储一条数据为当前博客的点赞用户标识，来区分哪个用户对文章进行了点赞，使用ZSet数据结构对点赞用户进行排序来实现排行榜功能

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学习产出：

解决方案：

1. 点赞后的用户记录在Redis的set数据类型中

1. 准备pom环境

		<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency><dependency><groupId>org.apache.commons</groupId><artifactId>commons-pool2</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope><version>5.1.47</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.4.3</version></dependency><!--hutool--><dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId><version>5.7.17</version></dependency><dependency><groupId>org.redisson</groupId><artifactId>redisson</artifactId><version>3.23.1</version></dependency>

2. 配置ThreadLocal和过滤器

public class UserHolder {private static final ThreadLocal<UserDTO> tl = new ThreadLocal<>();public static void saveUser(UserDTO user){tl.set(user);}public static UserDTO getUser(){return tl.get();}public static void removeUser(){tl.remove();}
}

@Configuration
public class MvcConfig implements WebMvcConfigurer {@Autowiredprivate StringRedisTemplate redis;@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(new LoginInterceptor()).excludePathPatterns("/user/code","/user/login","/blog/hot","/shop/**","/shop-type/**","/voucher/**").order(2);registry.addInterceptor(new RefreshTokenInterceptor(redis)).addPathPatterns("/**").order(1);}
}
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@Slf4j
public class LoginInterceptor implements HandlerInterceptor {//controller执行之前@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {//1.判断是否需要拦截ThreadLocalif (UserHolder.getUser()==null) {response.setStatus(401);return false;}//7.放行return true;}//渲染后返回给前台数据前@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {//移除用户，避免内存泄露UserHolder.removeUser();}
}
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@Slf4j
public class RefreshTokenInterceptor implements HandlerInterceptor {//这个对象不是由spring管理的所以不能用注解自动注入private StringRedisTemplate redis;public RefreshTokenInterceptor(StringRedisTemplate redis) {this.redis = redis;}//controller执行之前@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {//1.获取请求头中的tokenString token = request.getHeader("authorization");if (StrUtil.isBlank(token)) {return true;}//2.基于token获取redis中的用户//通过key取到hash中的map集合数据Map<Object, Object> userMap = redis.opsForHash().entries("login:token:" + token);//3.判断用户是否存在if (userMap.isEmpty()) {return true;}//5.将查询到的hash数据转为userDto对象UserDTO userDTO = BeanUtil.fillBeanWithMap(userMap, new UserDTO(), false);//6.存在，保存用户信息到ThreadLocal中UserHolder.saveUser(userDTO);//7.刷新token有效期redis.expire(LOGIN_USER_KEY + token, 30, TimeUnit.MINUTES);log.info("我是第一个拦截器当前拦截所有请求的用户为，线程为{},{}",UserHolder.getUser(),Thread.currentThread());//8.放行return true;}

3. Controller层：负责接收请求和向下分配

@RestController
@RequestMapping("/blog")
public class BlogController{@Resourceprivate IBlogService blogService;@PutMapping("/like/{id}")public Result likeBlog(@PathVariable("id") Long id) {return blogService.likeBlog(id);}
}

4. Service层：负责业务的处理逻辑点赞功能，将文章的点赞用户以时间戳为分数存入Redis

@Service
public class BlogServiceImpl extends ServiceImpl<BlogMapper, Blog> implements IBlogService {@Autowiredprivate IUserService userService;@Resourceprivate StringRedisTemplate redis;@Overridepublic Result likeBlog(Long id) {//1.获取登录用户Long userId = UserHolder.getUser().getId();//2.判断当前用户是否已经点赞String key = "blog:liked:" + id;//获取当前登录用户的分数，若文章中的用户id分数为null说明未点赞Double score = redis.opsForZSet().score(key, userId.toString());if (score == null) {//3.如果未点赞，可以点赞//3.1 点赞+1boolean isSuccess = update().setSql("liked= liked +1").eq("id", id).update();//3.2保存当前点赞用户到Redis的文章set集合中，文章set集合中记录的是点赞用户的id，//分数是时间戳，可以进行排序if (isSuccess) {//存入Redis的分数值以当前时间戳存入redis.opsForZSet().add(key, userId.toString(), System.currentTimeMillis());}} else {//4.如果已点赞，取消点赞//4.1点赞-1boolean isSuccess = update().setSql("liked = liked -1").eq("id", id).update();//4.2把用户从Redis的set集合移除if (isSuccess) {redis.opsForZSet().remove(key, userId.toString());}}return null;}
}

5. 上述为下面的排行榜做铺垫
查询当前文章的点赞排行榜，id是文章id号

	@PutMapping("/likes/{id}")public Result likesBlog(@PathVariable("id") Long id) {return blogService.queryBlogLikes(id);}

@Overridepublic Result queryBlogLikes(Long id) {String key="blog:liked:" + id;//取出前五条数据Set<String> rangeData = redis.opsForZSet().range(key, 0, 4);if (rangeData==null) {return Result.ok(Collections.emptyList());}//将文章点赞的前五条用户id转换为Long类型List<Long> ids = rangeData.stream().map(Long::valueOf).collect(Collectors.toList());String idStr = StrUtil.join(",", ids);//去数据库把这些用户查询出来，并且数据脱敏返回给前端List<User> users = userService.query().in("id",ids).last("order by field(id,"+idStr+")").list();UserDTO userData = BeanUtil.copyProperties(users, UserDTO.class);return Result.ok(userData);}