redis实现缓存3-封装redis工具类

具体实现：

CacheClient

package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

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.*;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    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
        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,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time, TimeUnit unit){
        // 1.从redis中查询商铺缓存
        String key = keyPrefix + id;
        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){
            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){

            //将空值写入reids
            stringRedisTemplate.opsForValue().set(key, "",CACHE_NULL_TTL, TimeUnit.MINUTES);

            return null;
        }
        // 6.存在，写入redis
        this.set(key, r, time, unit);
        // 7.返回
        return r;
    }



    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback,Long time, TimeUnit unit){
        // 1.从redis中查询商铺缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if(StrUtil.isBlank(json)){
            // 3.存在，直接返回
            return null;
        }

        // 4.命中，把json反序列化为对象
        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过期，要缓存重建
        // 6.重建缓存
        // 6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY +id;
        boolean isLock = tryLock(lockKey);
        // 6.2 判断是否获取锁成功
        if(isLock){
            // 6.3 成功，开启独立线程
            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 返回过期的店铺信息
        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);

    }
}

调用工具类：

    @Override
    public Result queryById(Long id) {
        // 逻辑过期解决缓存击穿
           Shop shop = cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY,id,Shop.class,this::getById,20L,TimeUnit.SECONDS);
        // 缓存穿透
        // Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);
        // 互斥锁解决缓存击穿
        // Shop shop = queryWithMutex(id);


        if (shop == null) {
            return Result.fail("店铺不存在！");
        }

        // 7.返回
        return Result.ok(shop);
    }