Redis缓存穿透/击穿工具类的封装

import lombok.Data;

import java.time.LocalDateTime;

@Data
public class RedisData {
    private LocalDateTime expireTime;
    private Object data;
}

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.JSON.jsONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {

    @Resource
    private final StringRedisTemplate stringRedisTemplate;

    // 线程池对象
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    
    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    
    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        // 设置逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        // 写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    
    public <R, T> R queryWithPassThrough(
            String keyPrefix, T id, Class<R> type, Function<T, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        // 1. 从 redis 查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2. 判断是否存在
        if (StrUtil.isNotBlank(json)) {
            // 3. 存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        // 判断命中的是否是空值
        if (json != null) {
            // 返回错误信息
            return null;
        }
        // 4. 不存在，根据id 查询数据库
        R r = dbFallback.apply(id);
        // 5. 不存在，返回错误
        if (r == null) {
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        // 6. 写入redis
        this.set(key, r, time, unit);
        // 7. 返回
        return r;
    }

    
    public <R, T> R queryWithLogicalExpire(
            String keyPrefix, T id, Class<R> type, Function<T, R> dbFallback, Long time, TimeUnit unit) {

        String key = keyPrefix + id;
        // 1. 从 redis 查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2. 判断是否存在
        if (StrUtil.isBlank(json)) {
            return null;
        }

        // 4. 命中需要判断过期时间
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5. 判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            // 5.1 未过期，直接返回店铺信息
            return r;
        }
        // 5.2 已过期，需要缓存重建
        // 6. 缓冲重建
        // 6.1 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        // 6.2 判断是否获取锁成功
        boolean isLock = tryLock(lockKey);
        if (isLock) {
            // 6.3 成功 开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    // 查询数据库
                    R r1 = dbFallback.apply(id);
                    // 写入Redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    // 释放锁
                    unlock(lockKey);
                }
            });
        }
        // 6.4 返回店铺信息
        return r;
    }

    
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    
    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }


}