/**
 * 嘗試獲取鎖
 *
 * @param key
 * @return
 */
private boolean tryLock(String key) {
    Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
    return BooleanUtil.isTrue(flag);
}
 
/**
 * 釋放鎖
 *
 * @param key
 */
private void unlock(String key) {
    stringRedisTemplate.delete(key);
}

    /**
     * 解決緩存擊穿的互斥鎖
     * @param id
     * @return
     */
    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.從Redis查詢(xún)緩存
        String shopJson = stringRedisTemplate.opsForValue().get(key);  //JSON格式
        //2.判斷是否存在
        if (StrUtil.isNotBlank(shopJson)) { //不為空就返回 此工具類(lèi)API會(huì)判斷" "為false
            //存在則直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            //return Result.ok(shop);
            return shop;
        }
        //3.判斷是否為空值 這里過(guò)濾 " "的情況，不用擔(dān)心會(huì)一直觸發(fā)這個(gè)條件因?yàn)樗蠺TL
        if (shopJson != null) {
            //返回一個(gè)空值
            return null;
        }
        //4.緩存重建 Redis中值為null的情況
        //4.1獲得互斥鎖
        String lockKey = "lock:shop"+id;
        Shop shopById=null;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2判斷是否獲取成功
            if (!isLock){
                //4.3失敗，則休眠并重試
                Thread.sleep(50);
               return queryWithMutex(id);
            }
            //4.4成功，根據(jù)id查詢(xún)數(shù)據(jù)庫(kù)
            shopById = getById(id);
            //5.不存在則返回錯(cuò)誤
            if (shopById == null) {
                //將空值寫(xiě)入Redis
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                //為什么這里要存一個(gè)" "這是因?yàn)槿绻罄m(xù)DB中有數(shù)據(jù)補(bǔ)充的話(huà)還可以去重建緩存
                //return Result.fail("暫無(wú)該商鋪信息");
                return null;
            }
            //6.存在，寫(xiě)入Redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shopById), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7.釋放互斥鎖
            unlock(lockKey);
        }
 
        return shopById;
    }

/**
 * 添加邏輯過(guò)期時(shí)間
 *
 * @param id
 * @param expireTime
 */
public void saveShopRedis(Long id, Long expireTime) {
    //查詢(xún)店鋪信息
    Shop shop = getById(id);
    //封裝邏輯過(guò)期時(shí)間
    RedisData redisData = new RedisData();
    redisData.setData(shop);
    redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireTime));
    //將封裝過(guò)期時(shí)間和商鋪數(shù)據(jù)的對(duì)象寫(xiě)入Redis
    stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
}

/**
 * 邏輯過(guò)期解決緩存擊穿
 *
 * @param id
 * @return
 */
public Shop queryWithLogicalExpire(Long id) throws InterruptedException {
    String key = CACHE_SHOP_KEY + id;
    Thread.sleep(200);
    //1.從Redis查詢(xún)緩存
    String shopJson = stringRedisTemplate.opsForValue().get(key);  //JSON格式
    //2.判斷是否存在
    if (StrUtil.isBlank(shopJson)) {
        //不存在則直接返回
        return null;
    }
    //3.判斷是否為空值
    if (shopJson != null) {
        //返回一個(gè)空值
        //return Result.fail("店鋪不存在！");
        return null;
    }
    //4.命中
    //4.1將JSON反序列化為對(duì)象
    RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
    Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
    LocalDateTime expireTime = redisData.getExpireTime();
    //4.2判斷是否過(guò)期
    if (expireTime.isAfter(LocalDateTime.now())) {
        //5.未過(guò)期則返回店鋪信息
        return shop;
    }
    //6.過(guò)期則緩存重建
    //6.1獲取互斥鎖
    String LockKey = LOCK_SHOP_KEY + id;
    boolean isLock = tryLock(LockKey);
    //6.2判斷是否成功獲得鎖
    if (isLock) {
        //6.3成功，開(kāi)啟獨(dú)立線(xiàn)程，實(shí)現(xiàn)緩存重建
        CACHE_REBUILD_EXECUTOR.submit(() -> {
            try {
                //重建緩存
                this.saveShop2Redis(id, 20L);
 
            } catch (Exception e) {
                throw new RuntimeException(e);
            } finally {
                //釋放鎖
                unlock(LockKey);
            }
        });
    }
    //6.4返回商鋪信息
    return shop;
}

import org.redisson.Redisson;
import org.redisson.api.RBucket;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;
 
public class RedissonExample {
    public static void main(String[] args) {
        Config config = new Config();
        config.useSingleServer().setAddress("redis://127.0.0.1:6379");
 
        RedissonClient redisson = Redisson.create(config);
 
        String key = "exampleKey";
        String value = "exampleValue";
        int timeout = 10; // 過(guò)期時(shí)間（秒）
 
        // 獲取RBucket對(duì)象
        RBucket<String> bucket = redisson.getBucket(key);
 
        // 設(shè)置值并指定過(guò)期時(shí)間
        bucket.set(value, timeout, TimeUnit.SECONDS);
 
        System.out.println("設(shè)置成功");
        redisson.shutdown();
    }
}