feat(singer): 实现歌手热度分计算和缓存机制

- 新增 HotSingerScoreUtil工具类，用于计算歌手热度分数
- 在 Singer 实体中添加 hotScore 字段，用于存储热度分数
- 在 SingerDTO 中添加 hotScore 字段，用于展示热度分数
- 修改 SingerServiceImpl 中的 getHotSinger 方法，支持从 Redis 缓存中获取热门歌手列表
- 实现定时任务和异步方法，用于定期更新和缓存热门歌手列表

music-houduan/src/main/java/com/test/musichouduan/dto/SingerDTO.java

@@ -60,4 +60,9 @@ public class SingerDTO {
      * 关联音乐列表
      */
     private List<MusicDTO> musics;
+
+    /**
+     * 热度分
+     */
+    private double hotScore;
 }

music-houduan/src/main/java/com/test/musichouduan/entity/Singer.java

@@ -84,4 +84,10 @@ public class Singer {
         inverseJoinColumns = @JoinColumn(name = "music_id")
     )
     private Set<Music> musics = new HashSet<>();
+
+    /**
+     * 热度分，不持久化到数据库
+     */
+    @Transient
+    private double hotScore;
 }

music-houduan/src/main/java/com/test/musichouduan/service/impl/SingerServiceImpl.java

@@ -14,10 +14,20 @@ import com.test.musichouduan.repository.MusicRepository;
 import com.test.musichouduan.repository.SingerRepository;
 import com.test.musichouduan.repository.SingerTypeRepository;
 import com.test.musichouduan.repository.UserRepository;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
 import com.test.musichouduan.repository.UserSingerRepository;
 import com.test.musichouduan.service.FileService;
 import com.test.musichouduan.service.SingerService;
+import com.test.musichouduan.util.HotSingerScoreUtil;
 import org.springframework.beans.BeanUtils;
+import org.springframework.data.redis.core.StringRedisTemplate;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.util.CollectionUtils;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+import java.util.Comparator;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
@@ -39,6 +49,16 @@ import java.util.stream.Collectors;
 @Service
 public class SingerServiceImpl implements SingerService {
 
+    private static final String HOT_SINGER_CACHE_KEY = "singer:hot_list";
+    private static final long CACHE_EXPIRATION_HOURS = 2;
+    private static final int HOT_SINGER_LIMIT = 50;
+
+    @Autowired
+    private StringRedisTemplate redisTemplate;
+
+    @Autowired
+    private ObjectMapper objectMapper;
+
     @Autowired
     private SingerRepository singerRepository;
 
@@ -115,13 +135,64 @@ public class SingerServiceImpl implements SingerService {
 
     @Override
     public List<SingerDTO> getHotSinger(Integer limit) {
-        // 查询热门歌手
-        List<Singer> singers = singerRepository.findHotSingers(PageRequest.of(0, limit));
+        String hotSingerJson = redisTemplate.opsForValue().get(HOT_SINGER_CACHE_KEY);
 
-        // 转换为DTO
-        return singers.stream()
+        if (StringUtils.hasText(hotSingerJson)) {
+            try {
+                List<SingerDTO> cachedList = objectMapper.readValue(hotSingerJson, new TypeReference<List<SingerDTO>>() {});
+                return cachedList.stream().limit(limit).collect(Collectors.toList());
+            } catch (Exception e) {
+                System.err.println("Failed to deserialize hot singer list from Redis: " + e.getMessage());
+            }
+        }
+
+        List<SingerDTO> hotList = calculateAndCacheHotSingerSync();
+        return hotList.stream().limit(limit).collect(Collectors.toList());
+    }
+
+    private List<SingerDTO> calculateAndCacheHotSingerSync() {
+        try {
+            return updateHotSingerCache().get();
+        } catch (Exception e) {
+            System.err.println("Failed to calculate hot singer list synchronously: " + e.getMessage());
+            List<Singer> singers = singerRepository.findHotSingers(PageRequest.of(0, HOT_SINGER_LIMIT));
+            return singers.stream()
+                    .map(this::convertToDTO)
+                    .collect(Collectors.toList());
+        }
+    }
+
+    @Scheduled(cron = "0 0 * * * ?")
+    public void scheduleUpdateHotSinger() {
+        System.out.println("Scheduled task started: Updating hot singer cache...");
+        updateHotSingerCache();
+    }
+
+    @Async
+    @Transactional(readOnly = true)
+    public CompletableFuture<List<SingerDTO>> updateHotSingerCache() {
+        List<Singer> allSingers = singerRepository.findAll();
+
+        allSingers.parallelStream().forEach(singer -> {
+            double score = HotSingerScoreUtil.calculateHotScore(singer);
+            singer.setHotScore(score);
+        });
+
+        List<SingerDTO> sortedHotSingers = allSingers.stream()
+                .sorted(Comparator.comparing(Singer::getHotScore).reversed())
+                .limit(HOT_SINGER_LIMIT)
                 .map(this::convertToDTO)
                 .collect(Collectors.toList());
+
+        try {
+            String jsonToCache = objectMapper.writeValueAsString(sortedHotSingers);
+            redisTemplate.opsForValue().set(HOT_SINGER_CACHE_KEY, jsonToCache, CACHE_EXPIRATION_HOURS, TimeUnit.HOURS);
+            System.out.println("Hot singer cache updated successfully with " + sortedHotSingers.size() + " items.");
+        } catch (Exception e) {
+            System.err.println("Failed to cache hot singer list to Redis: " + e.getMessage());
+        }
+
+        return CompletableFuture.completedFuture(sortedHotSingers);
     }
 
     @Override
@@ -356,6 +427,7 @@ public class SingerServiceImpl implements SingerService {
     private SingerDTO convertToDTO(Singer singer) {
         SingerDTO singerDTO = new SingerDTO();
         BeanUtils.copyProperties(singer, singerDTO);
+        singerDTO.setHotScore(singer.getHotScore());
 
         // 设置类型信息
         if (singer.getType() != null) {

music-houduan/src/main/java/com/test/musichouduan/util/HotSingerScoreUtil.java

@@ -0,0 +1,44 @@
+package com.test.musichouduan.util;
+
+import com.test.musichouduan.entity.Singer;
+import java.time.Duration;
+import java.time.LocalDateTime;
+
+/**
+ * 歌手热度分数计算工具类
+ */
+public class HotSingerScoreUtil {
+
+    // 定义各种交互的权重
+    private static final double FANS_WEIGHT = 2.0; // 粉丝数（收藏数）
+    private static final double COMMENT_WEIGHT = 1.5;
+
+    // 时间衰减因子中的指数
+    private static final double TIME_DECAY_EXPONENT = 1.8;
+
+    /**
+     * 计算单个歌手的热度分数
+     * 算法: 热度 = (交互权重和) / (时间衰减因子)
+     *
+     * @param singer 歌手实体对象
+     * @return 计算出的热度分数
+     */
+    public static double calculateHotScore(Singer singer) {
+        // 1. 计算交互权重和
+        long fansCount = singer.getCollectCount() != null ? singer.getCollectCount() : 0;
+        long commentCount = singer.getCommentCount() != null ? singer.getCommentCount() : 0;
+
+        double interactionScore = (fansCount * FANS_WEIGHT) +
+                                  (commentCount * COMMENT_WEIGHT);
+
+        // 2. 计算时间衰减因子
+        LocalDateTime createTime = singer.getCreateTime();
+        LocalDateTime now = LocalDateTime.now();
+        long hoursElapsed = Duration.between(createTime, now).toHours();
+
+        double timeDecayFactor = Math.pow(hoursElapsed + 2, TIME_DECAY_EXPONENT);
+
+        // 3. 计算最终热度分数
+        return interactionScore / timeDecayFactor;
+    }
+}