<dependencies>
    <!-- 使用 jedis 客户端添加以下依赖 -->
    <dependency>
        <groupId>com.alicp.jetcache</groupId>
        <artifactId>jetcache-starter-redis</artifactId>
        <version>${version}</version>
    </dependency>
    <!-- 使用 lettuce 客户端添加以下依赖 -->
    <dependency>
        <groupId>com.alicp.jetcache</groupId>
        <artifactId>jetcache-starter-redis-lettuce</artifactId>
        <version>${version}</version>
    </dependency>
</dependencies>

jetcache:
  statIntervalMinutes: 60
  areaInCacheName: false
  penetrationProtect: false
  enableMethodCache: true
  hiddenPackages: com.xxx.xxx,com.xxx.xxx
  local:
    default:
      type: caffeine # 支持的类型：linkedhashmap、caffeine
      limit: 100
      keyConvertor: fastjson # 支持的类型：fastjson，可自定义转换器函数
      expireAfterWriteInMillis: 600000
      expireAfterAccessInMillis: 300000 
  remote:
    default:
      type: redis.lettuce # 支持的类型：redis、redis.lettuce
      keyPrefix: '系统简称:所属名字:'
      keyConvertor: fastjson
      valueEncoder: java # 支持的类型：kryo、java，可自定义编码器
      valueDecoder: java # 支持的类型：kryo、java，可自定义解码器
      expireAfterWriteInMillis: 3600000
      #readFrom: slavePreferred # 优先从Slave节点中读取
      uri: redis-sentinel://host1:26379,host2:26379,host3:26379/?sentinelMasterId=mymaster # 哨兵模式
      #uri: redis://127.0.0.1:6379/ # 单节点模式
      #mode: masterslave # 设置为主从模式
      #uri: # 集群模式
      #- redis://127.0.0.1:7000
      #- redis://127.0.0.1:7001
      #- redis://127.0.0.1:7002
    example:
      keyPrefix: '系统简称:所属名字:'
      type: redis
      keyConvertor: fastjson
      valueEncoder: java
      valueDecoder: java
      expireAfterWriteInMillis: 3600000
      poolConfig:
        minIdle: 10
        maxIdle: 20
        maxTotal: 50
      #password: xxx # 连接密码
      #timeout: 2000 # 连接的超时时间，读取数据的超时时间
      #database: 0 # 连接的数据库
      #clientName: null # 客户端名称
      #ssl: 是否使用SSL
      host: ${redis.host}
      port: ${redis.port}
      #sentinel: host1:26379,host2:26379,host3:26379 # 哨兵模式
      #masterName: mymaster

/**
 * 启动类
 */
@SpringBootApplication
@EnableCreateCacheAnnotation
@EnableMethodCache(basePackages = "com.xxx.xxx")
public class Application {
    public static void main(String[] args){
        SpringApplication.run(Application.class, args);
    }
}

/**
 * 接口
 */
public interface JetCacheExampleService {
    
    User getValue(long userId);
    
    void updateValue(User  user);
    
    void deleteValue(User  user);
}

/**
 * 实现类
 */
@Service
public class JetCacheExampleServiceImpl implements JetCacheExampleService {
    
    @CreateCache(name = "JetCacheExampleServiceImpl.exampleCache" , localLimit = 50 ,cacheType = CacheType.LOCAL)
    @CachePenetrationProtect
    private Cache<Long, User> exampleCache;
    
    @Override
    @Cached(name = "JetCacheExampleService.getValue", expire = 3600 * 6, localLimit = 50, cacheType = CacheType.BOTH)
    @CacheRefresh(refresh = 3600, stopRefreshAfterLastAccess = 3600 * 2)
    @CachePenetrationProtect
    public User getValue(long userId){
        String result = new User();
        // ... 处理逻辑
        return result;
    }
    
    @Override
    @CacheUpdate(name = "JetCacheExampleService.getValue", key="#user.userId", value="#user")
    public void updateValue(User user){
        // 处理逻辑
    }
    
    @Override
    @CacheInvalidate(name = "JetCacheExampleService.getValue", key="#user.userId")
    public void deleteValue(User user){
        // 处理逻辑
    }
    
}

@Service
public class JetCacheExampleServiceImpl implements JetCacheExampleService {
    
	@CreateCache(name = "JetCacheExampleServiceImpl.exampleCache" , localLimit = 50 ,cacheType = CacheType.LOCAL)
	private Cache<Long, User> exampleCache;

	@PostConstruct
	public exampleCacheInit(){
    	RefreshPolicy policy = RefreshPolicy.newPolicy(60, TimeUnit.MINUTES)
                	.stopRefreshAfterLastAccess(120, TimeUnit.MINUTES);
        exampleCache.config().setLoader(this::loadFromDatabase);
        exampleCache.config().setRefreshPolicy(policy);
	}
}

public interface Cache<K, V> extends Closeable {

    Logger logger = LoggerFactory.getLogger(Cache.class);

    //-----------------------------JSR 107 style API------------------------------------------------
    default V get(K key) throws CacheInvokeException {
        CacheGetResult<V> result = GET(key);
        if (result.isSuccess()) {
            return result.getValue();
        } else {
            return null;
        }
    }
    default Map<K, V> getAll(Set<? extends K> keys) throws CacheInvokeException {
        MultiGetResult<K, V> cacheGetResults = GET_ALL(keys);
        return cacheGetResults.unwrapValues();
    }
    default void put(K key, V value) {
        PUT(key, value);
    }
    default void putAll(Map<? extends K, ? extends V> map) {
        PUT_ALL(map);
    }
    default boolean putIfAbsent(K key, V value) { // 多级缓存MultiLevelCache不支持此方法
        CacheResult result = PUT_IF_ABSENT(key, value, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
        return result.getResultCode() == CacheResultCode.SUCCESS;
    }
    default boolean remove(K key) {
        return REMOVE(key).isSuccess();
    }
    default void removeAll(Set<? extends K> keys) {
        REMOVE_ALL(keys);
    }
    <T> T unwrap(Class<T> clazz);

    @Override
    default void close() {
    }

    //--------------------------JetCache API---------------------------------------------
    CacheConfig<K, V> config();

    default AutoReleaseLock tryLock(K key, long expire, TimeUnit timeUnit) {
        if (key == null) {
            return null;
        }
        // 随机生成一个值
        final String uuid = UUID.randomUUID().toString();
        // 过期时间
        final long expireTimestamp = System.currentTimeMillis() + timeUnit.toMillis(expire);
        final CacheConfig config = config();

        AutoReleaseLock lock = () -> { // 创建一把会自动释放资源的锁，实现其 close() 方法
            int unlockCount = 0;
            while (unlockCount++ < config.getTryLockUnlockCount()) {
                if(System.currentTimeMillis() < expireTimestamp) { // 这把锁还没有过期，则删除
                    // 删除对应的 Key 值
                    // 出现的结果：成功，失败，Key 不存在
                    CacheResult unlockResult = REMOVE(key);
                    if (unlockResult.getResultCode() == CacheResultCode.FAIL
                            || unlockResult.getResultCode() == CacheResultCode.PART_SUCCESS) {
                        // 删除对应的 Key 值过程中出现了异常，则重试
                        logger.info("[tryLock] [{} of {}] [{}] unlock failed. Key={}, msg = {}",
                                unlockCount, config.getTryLockUnlockCount(), uuid, key, unlockResult.getMessage());
                        // retry
                    } else if (unlockResult.isSuccess()) { // 释放成功
                        logger.debug("[tryLock] [{} of {}] [{}] successfully release the lock. Key={}",
                                unlockCount, config.getTryLockUnlockCount(), uuid, key);
                        return;
                    } else { // 锁已经被释放了
                        logger.warn("[tryLock] [{} of {}] [{}] unexpected unlock result: Key={}, result={}",
                                unlockCount, config.getTryLockUnlockCount(), uuid, key, unlockResult.getResultCode());
                        return;
                    }
                } else { // 该锁已失效
                    logger.info("[tryLock] [{} of {}] [{}] lock already expired: Key={}",
                            unlockCount, config.getTryLockUnlockCount(), uuid, key);
                    return;
                }
            }
        };

        int lockCount = 0;
        Cache cache = this;
        while (lockCount++ < config.getTryLockLockCount()) {
            // 往 Redis（或者本地） 中存放 Key 值（_#RL#结尾的Key）
            // 返回的结果：成功、已存在、失败
            CacheResult lockResult = cache.PUT_IF_ABSENT(key, uuid, expire, timeUnit);
            if (lockResult.isSuccess()) { // 成功获取到锁
                logger.debug("[tryLock] [{} of {}] [{}] successfully get a lock. Key={}",
                        lockCount, config.getTryLockLockCount(), uuid, key);
                return lock;
            } else if (lockResult.getResultCode() == CacheResultCode.FAIL || lockResult.getResultCode() == CacheResultCode.PART_SUCCESS) {
                logger.info("[tryLock] [{} of {}] [{}] cache access failed during get lock, will inquiry {} times. Key={}, msg={}",
                        lockCount, config.getTryLockLockCount(), uuid,
                        config.getTryLockInquiryCount(), key, lockResult.getMessage());
                // 尝试获取锁的过程中失败了，也就是往 Redis 中存放 Key 值出现异常
                // 这个时候可能 Key 值已经存储了，但是由于其他原因导致返回的结果表示执行失败
                int inquiryCount = 0;
                while (inquiryCount++ < config.getTryLockInquiryCount()) {
                    CacheGetResult inquiryResult = cache.GET(key);
                    if (inquiryResult.isSuccess()) {
                        if (uuid.equals(inquiryResult.getValue())) {
                            logger.debug("[tryLock] [{} of {}] [{}] successfully get a lock after inquiry. Key={}",
                                    inquiryCount, config.getTryLockInquiryCount(), uuid, key);
                            return lock;
                        } else {
                            logger.debug("[tryLock] [{} of {}] [{}] not the owner of the lock, return null. Key={}",
                                    inquiryCount, config.getTryLockInquiryCount(), uuid, key);
                            return null;
                        }
                    } else {
                        logger.info("[tryLock] [{} of {}] [{}] inquiry failed. Key={}, msg={}",
                                inquiryCount, config.getTryLockInquiryCount(), uuid, key, inquiryResult.getMessage());
                        // retry inquiry
                    }
                }
            } else { // 已存在表示该锁被其他人占有
                // others holds the lock
                logger.debug("[tryLock] [{} of {}] [{}] others holds the lock, return null. Key={}",
                        lockCount, config.getTryLockLockCount(), uuid, key);
                return null;
            }
        }

        logger.debug("[tryLock] [{}] return null after {} attempts. Key={}", uuid, config.getTryLockLockCount(), key);
        return null;
    }

    default boolean tryLockAndRun(K key, long expire, TimeUnit timeUnit, Runnable action){
        // Release the lock use Java 7 try-with-resources.
        try (AutoReleaseLock lock = tryLock(key, expire, timeUnit)) { // 尝试获取锁
            if (lock != null) { // 获取到锁则执行下面的任务
                action.run();
                return true;
            } else {
                return false;
            }
            // 执行完锁的操作后会进行资源释放，调用 AutoCloseable 的 close() 方法
        }
    }

    CacheGetResult<V> GET(K key);

    MultiGetResult<K, V> GET_ALL(Set<? extends K> keys);

    default V computeIfAbsent(K key, Function<K, V> loader) {
        return computeIfAbsent(key, loader, config().isCacheNullValue());
    }

    V computeIfAbsent(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull);

    V computeIfAbsent(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull, long expireAfterWrite, TimeUnit timeUnit);

    default void put(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
        PUT(key, value, expireAfterWrite, timeUnit);
    }

    default CacheResult PUT(K key, V value) {
        if (key == null) {
            return CacheResult.FAIL_ILLEGAL_ARGUMENT;
        }
        return PUT(key, value, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
    }

    CacheResult PUT(K key, V value, long expireAfterWrite, TimeUnit timeUnit);

    default void putAll(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit) {
        PUT_ALL(map, expireAfterWrite, timeUnit);
    }

    default CacheResult PUT_ALL(Map<? extends K, ? extends V> map) {
        if (map == null) {
            return CacheResult.FAIL_ILLEGAL_ARGUMENT;
        }
        return PUT_ALL(map, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
    }

    CacheResult PUT_ALL(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit);

    CacheResult REMOVE(K key);

    CacheResult REMOVE_ALL(Set<? extends K> keys);

    CacheResult PUT_IF_ABSENT(K key, V value, long expireAfterWrite, TimeUnit timeUnit);

}

public abstract class AbstractCache<K, V> implements Cache<K, V> {

    /**
     * 当缓存未命中时，并发情况同一个Key是否只允许一个线程去加载，其他线程等待结果（可以设置timeout，超时则自己加载并直接返回）
     * 如果是的话则由获取到Key对应的 LoaderLock.signal（采用了 CountDownLatch）的线程进行加载
     * loaderMap临时保存 Key 对应的 LoaderLock 对象
     */
    private volatile ConcurrentHashMap<Object, LoaderLock> loaderMap;

    ConcurrentHashMap<Object, LoaderLock> initOrGetLoaderMap() {
        if (loaderMap == null) {
            synchronized (this) {
                if (loaderMap == null) {
                    loaderMap = new ConcurrentHashMap<>();
                }
            }
        }
        return loaderMap;
    }

    @Override
    public final V computeIfAbsent(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull) {
        return computeIfAbsentImpl(key, loader, cacheNullWhenLoaderReturnNull,
                0, null, this);
    }

    @Override
    public final V computeIfAbsent(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull,
                                   long expireAfterWrite, TimeUnit timeUnit) {
        return computeIfAbsentImpl(key, loader, cacheNullWhenLoaderReturnNull,
                expireAfterWrite, timeUnit, this);
    }

    private static <K, V> boolean needUpdate(V loadedValue, boolean cacheNullWhenLoaderReturnNull, Function<K, V> loader) {
        if (loadedValue == null && !cacheNullWhenLoaderReturnNull) {
            return false;
        }
        if (loader instanceof CacheLoader && ((CacheLoader<K, V>) loader).vetoCacheUpdate()) {
            return false;
        }
        return true;
    }

    static <K, V> V computeIfAbsentImpl(K key, Function<K, V> loader, boolean cacheNullWhenLoaderReturnNull,
                                               long expireAfterWrite, TimeUnit timeUnit, Cache<K, V> cache) {
    	// 获取内部的 Cache 对象
        AbstractCache<K, V> abstractCache = CacheUtil.getAbstractCache(cache);
        // 封装 loader 函数成一个 ProxyLoader 对象，主要在重新加载缓存后发出一个 CacheLoadEvent 到 CacheMonitor
        CacheLoader<K, V> newLoader = CacheUtil.createProxyLoader(cache, loader, abstractCache::notify);
        CacheGetResult<V> r;
        if (cache instanceof RefreshCache) { // 该缓存实例需要刷新
            RefreshCache<K, V> refreshCache = ((RefreshCache<K, V>) cache);
            /*
             * 从缓存中获取数据
             * 如果是多级缓存（先从本地缓存获取，获取不到则从远程缓存获取）
             * 如果缓存数据是从远程缓存获取到的数据则会更新至本地缓存，并且如果本地缓存没有设置 localExpire 则使用远程缓存的到期时间作为自己的到期时间
             * 我一般不设置 localExpire ，因为可能导致本地缓存的有效时间比远程缓存的有效时间更长
             * 如果设置 localExpire 了记得设置 expireAfterAccessInMillis
             */
            r = refreshCache.GET(key);
            // 添加/更新当前 RefreshCache 的刷新缓存任务，存放于 RefreshCache 的 taskMap 中
            refreshCache.addOrUpdateRefreshTask(key, newLoader);
        } else {
            // 从缓存中获取数据
            r = cache.GET(key);
        }
        if (r.isSuccess()) { // 缓存命中
            return r.getValue();
        } else { // 缓存未命中
            // 创建当缓存未命中去更新缓存的函数
            Consumer<V> cacheUpdater = (loadedValue) -> {
                if(needUpdate(loadedValue, cacheNullWhenLoaderReturnNull, newLoader)) {
                    /*
                     * 未在缓存注解中配置 key 的生成方式则默认取入参作为缓存 key
                     * 在进入当前方法时是否可以考虑为 key 创建一个副本？？？？
                     * 因为缓存未命中然后通过 loader 重新加载方法时，如果方法内部对入参进行了修改，那么生成的缓存 key 也会被修改
                     * 从而导致相同的 key 进入该方法时一直与缓存中的 key 不相同，一直出现缓存未命中
                     */
                    if (timeUnit != null) {
                        cache.PUT(key, loadedValue, expireAfterWrite, timeUnit).waitForResult();
                    } else {
                        cache.PUT(key, loadedValue).waitForResult();
                    }
                }
            };

            V loadedValue;
            if (cache.config().isCachePenetrationProtect()) { // 添加了 @CachePenetrationProtect 注解
            	// 一个JVM只允许一个线程执行
                loadedValue = synchronizedLoad(cache.config(), abstractCache, key, newLoader, cacheUpdater);
            } else {
            	// 执行方法
                loadedValue = newLoader.apply(key);
                // 将新的结果异步缓存
                cacheUpdater.accept(loadedValue);
            }

            return loadedValue;
        }
    }

    static <K, V> V synchronizedLoad(CacheConfig config, AbstractCache<K,V> abstractCache,
                                     K key, Function<K, V> newLoader, Consumer<V> cacheUpdater) {
        ConcurrentHashMap<Object, LoaderLock> loaderMap = abstractCache.initOrGetLoaderMap();
        Object lockKey = buildLoaderLockKey(abstractCache, key);
        while (true) {
            // 为什么加一个 create[] 数组 疑问？？
            boolean create[] = new boolean[1];
            LoaderLock ll = loaderMap.computeIfAbsent(lockKey, (unusedKey) -> {
                create[0] = true;
                LoaderLock loaderLock = new LoaderLock();
                loaderLock.signal = new CountDownLatch(1);
                loaderLock.loaderThread = Thread.currentThread();
                return loaderLock;
            });
            if (create[0] || ll.loaderThread == Thread.currentThread()) {
                try {
                    // 加载该 Key 实例的方法
                    V loadedValue = newLoader.apply(key);
                    ll.success = true;
                    ll.value = loadedValue;
                    // 将重新加载的数据更新至缓存
                    cacheUpdater.accept(loadedValue);
                    return loadedValue;
                } finally {
                    // 标记已完成
                    ll.signal.countDown();
                    if (create[0]) {
                        loaderMap.remove(lockKey);
                    }
                }
            } else { // 等待其他线程加载，如果出现异常或者超时则自己加载返回数据，但是不更新缓存
                try {
                    Duration timeout = config.getPenetrationProtectTimeout();
                    if (timeout == null) {
                        ll.signal.await();
                    } else {
                        boolean ok = ll.signal.await(timeout.toMillis(), TimeUnit.MILLISECONDS);
                        if(!ok) {
                            logger.info("loader wait timeout:" + timeout);
                            return newLoader.apply(key);
                        }
                    }
                } catch (InterruptedException e) {
                    logger.warn("loader wait interrupted");
                    return newLoader.apply(key);
                }
                if (ll.success) {
                    return (V) ll.value;
                } else {
                    continue;
                }

            }
        }
    }

    private static Object buildLoaderLockKey(Cache c, Object key) {
        if (c instanceof AbstractEmbeddedCache) {
            return ((AbstractEmbeddedCache) c).buildKey(key);
        } else if (c instanceof AbstractExternalCache) {
            byte bytes[] = ((AbstractExternalCache) c).buildKey(key);
            return ByteBuffer.wrap(bytes);
        } else if (c instanceof MultiLevelCache) {
            c = ((MultiLevelCache) c).caches()[0];
            return buildLoaderLockKey(c, key);
        } else if(c instanceof ProxyCache) {
            c = ((ProxyCache) c).getTargetCache();
            return buildLoaderLockKey(c, key);
        } else {
            throw new CacheException("impossible");
        }
    }

    /**
     * 重新加载数据锁
     */
    static class LoaderLock {
        /**
         * 栅栏
         */
        CountDownLatch signal;
        /**
         * 持有的线程
         */
        Thread loaderThread;
        /**
         * 是否加载成功
         */
        boolean success;
        /**
         * 加载出来的数据
         */，
        Object value;
    }
}

public abstract class AbstractEmbeddedCache<K, V> extends AbstractCache<K, V> {
    protected EmbeddedCacheConfig<K, V> config;
    /**
     * 本地缓存的 Map
     */
    protected InnerMap innerMap;

    protected abstract InnerMap createAreaCache();

    public AbstractEmbeddedCache(EmbeddedCacheConfig<K, V> config) {
        this.config = config;
        innerMap = createAreaCache();
    }

    @Override
    public CacheConfig<K, V> config() {
        return config;
    }

    public Object buildKey(K key) {
        Object newKey = key;
        Function<K, Object> keyConvertor = config.getKeyConvertor();
        if (keyConvertor != null) {
            newKey = keyConvertor.apply(key);
        }
        return newKey;
    }

    @Override
    protected CacheGetResult<V> do_GET(K key) {
        Object newKey = buildKey(key);
        CacheValueHolder<V> holder = (CacheValueHolder<V>) innerMap.getValue(newKey);
        return parseHolderResult(holder);
    }

    protected CacheGetResult<V> parseHolderResult(CacheValueHolder<V> holder) {
        long now = System.currentTimeMillis();
        if (holder == null) {
            return CacheGetResult.NOT_EXISTS_WITHOUT_MSG;
        } else if (now >= holder.getExpireTime()) {
            return CacheGetResult.EXPIRED_WITHOUT_MSG;
        } else {
            synchronized (holder) {
                long accessTime = holder.getAccessTime();
                if (config.isExpireAfterAccess()) {
                    long expireAfterAccess = config.getExpireAfterAccessInMillis();
                    if (now >= accessTime + expireAfterAccess) {
                        return CacheGetResult.EXPIRED_WITHOUT_MSG;
                    }
                }
                // 设置该缓存数据的最后一次访问时间
                holder.setAccessTime(now);
            }

            return new CacheGetResult(CacheResultCode.SUCCESS, null, holder);
        }
    }

    @Override
    protected MultiGetResult<K, V> do_GET_ALL(Set<? extends K> keys) {
        ArrayList<K> keyList = new ArrayList<K>(keys.size());
        ArrayList<Object> newKeyList = new ArrayList<Object>(keys.size());
        keys.stream().forEach((k) -> {
            Object newKey = buildKey(k);
            keyList.add(k);
            newKeyList.add(newKey);
        });
        Map<Object, CacheValueHolder<V>> innerResultMap = innerMap.getAllValues(newKeyList);
        Map<K, CacheGetResult<V>> resultMap = new HashMap<>();
        for (int i = 0; i < keyList.size(); i++) {
            K key = keyList.get(i);
            Object newKey = newKeyList.get(i);
            CacheValueHolder<V> holder = innerResultMap.get(newKey);
            resultMap.put(key, parseHolderResult(holder));
        }
        MultiGetResult<K, V> result = new MultiGetResult<>(CacheResultCode.SUCCESS, null, resultMap);
        return result;
    }

    @Override
    protected CacheResult do_PUT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
        CacheValueHolder<V> cacheObject = new CacheValueHolder(value ,timeUnit.toMillis(expireAfterWrite));
        innerMap.putValue(buildKey(key), cacheObject);
        return CacheResult.SUCCESS_WITHOUT_MSG;
    }

    @Override
    protected CacheResult do_PUT_ALL(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit) {
        HashMap newKeyMap = new HashMap();
        for (Map.Entry<? extends K, ? extends V> en : map.entrySet()) {
            CacheValueHolder<V> cacheObject = new CacheValueHolder(en.getValue(), timeUnit.toMillis(expireAfterWrite));
            newKeyMap.put(buildKey(en.getKey()), cacheObject);
        }
        innerMap.putAllValues(newKeyMap);

        final HashMap resultMap = new HashMap();
        map.keySet().forEach((k) -> resultMap.put(k, CacheResultCode.SUCCESS));
        return CacheResult.SUCCESS_WITHOUT_MSG;
    }

    @Override
    protected CacheResult do_REMOVE(K key) {
        innerMap.removeValue(buildKey(key));
        return CacheResult.SUCCESS_WITHOUT_MSG;
    }

    @Override
    protected CacheResult do_REMOVE_ALL(Set<? extends K> keys) {
        Set newKeys = keys.stream().map((key) -> buildKey(key)).collect(Collectors.toSet());
        innerMap.removeAllValues(newKeys);

        final HashMap resultMap = new HashMap();
        keys.forEach((k) -> resultMap.put(k, CacheResultCode.SUCCESS));
        return CacheResult.SUCCESS_WITHOUT_MSG;
    }

    @Override
    protected CacheResult do_PUT_IF_ABSENT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
        CacheValueHolder<V> cacheObject = new CacheValueHolder(value, timeUnit.toMillis(expireAfterWrite));
        if (innerMap.putIfAbsentValue(buildKey(key), cacheObject)) {
            return CacheResult.SUCCESS_WITHOUT_MSG;
        } else {
            return CacheResult.EXISTS_WITHOUT_MSG;
        }
    }
}

public class LinkedHashMapCache<K, V> extends AbstractEmbeddedCache<K, V> {

    private static Logger logger = LoggerFactory.getLogger(LinkedHashMapCache.class);

    public LinkedHashMapCache(EmbeddedCacheConfig<K, V> config) {
        super(config);
        // 将缓存实例添加至 Cleaner
        addToCleaner();
    }

    protected void addToCleaner() {
        Cleaner.add(this);
    }

    @Override
    protected InnerMap createAreaCache() {
        return new LRUMap(config.getLimit(), this);
    }

    public void cleanExpiredEntry() {
        ((LRUMap) innerMap).cleanExpiredEntry();
    }

    /**
     * 用于本地缓存类型为 linkedhashmap 缓存实例存储缓存数据
     */
    final class LRUMap extends LinkedHashMap implements InnerMap {

        /**
         * 允许的最大缓存数量
         */
        private final int max;
        /**
         * 缓存实例锁
         */
        private Object lock;

        public LRUMap(int max, Object lock) {
            super((int) (max * 1.4f), 0.75f, true);
            this.max = max;
            this.lock = lock;
        }

        /**
         * 当元素大于最大值时移除最老的元素
         *
         * @param eldest 最老的元素
         * @return 是否删除
         */
        @Override
        protected boolean removeEldestEntry(Map.Entry eldest) {
            return size() > max;
        }

        /**
         * 清理过期的元素
         */
        void cleanExpiredEntry() {
            synchronized (lock) { // 占有当前缓存实例这把锁
                for (Iterator it = entrySet().iterator(); it.hasNext();) {
                    Map.Entry en = (Map.Entry) it.next();
                    Object value = en.getValue();
                    if (value != null && value instanceof CacheValueHolder) {
                        CacheValueHolder h = (CacheValueHolder) value;
                        /*
                         * 缓存的数据已经失效了则删除
                         * 为什么不对 expireAfterAccess 进行判断，取最小值，疑问？？？？
                         */
                        if (System.currentTimeMillis() >= h.getExpireTime()) {
                            it.remove();
                        }
                    } else {
                        // assert false
                        if (value == null) {
                            logger.error("key " + en.getKey() + " is null");
                        } else {
                            logger.error("value of key " + en.getKey() + " is not a CacheValueHolder. type=" + value.getClass());
                        }
                    }
                }
            }
        }

        @Override
        public Object getValue(Object key) {
            synchronized (lock) {
                return get(key);
            }
        }

        @Override
        public Map getAllValues(Collection keys) {
            Map values = new HashMap();
            synchronized (lock) {
                for (Object key : keys) {
                    Object v = get(key);
                    if (v != null) {
                        values.put(key, v);
                    }
                }
            }
            return values;
        }

        @Override
        public void putValue(Object key, Object value) {
            synchronized (lock) {
                put(key, value);
            }
        }

        @Override
        public void putAllValues(Map map) {
            synchronized (lock) {
                Set<Map.Entry> set = map.entrySet();
                for (Map.Entry en : set) {
                    put(en.getKey(), en.getValue());
                }
            }
        }

        @Override
        public boolean removeValue(Object key) {
            synchronized (lock) {
                return remove(key) != null;
            }
        }

        @Override
        public void removeAllValues(Collection keys) {
            synchronized (lock) {
                for (Object k : keys) {
                    remove(k);
                }
            }
        }

        @Override
        @SuppressWarnings("unchecked")
        public boolean putIfAbsentValue(Object key, Object value) {
            /*
             * 如果缓存 key 不存在，或者对应的 value 已经失效则放入，否则返回 false
             */
            synchronized (lock) {
                CacheValueHolder h = (CacheValueHolder) get(key);
                if (h == null || parseHolderResult(h).getResultCode() == CacheResultCode.EXPIRED) {
                    put(key, value);
                    return true;
                } else {
                    return false;
                }
            }
        }
    }

}

/**
 * 执行任务：定时清理（每分钟） LinkedHashMapCache 缓存实例中过期的缓存数据
 */
class Cleaner {
    /**
     * 存放弱引用对象，以防内存溢出
     * 如果被弱引用的对象只被当前弱引用对象关联时，gc 时被弱引用的对象则会被回收（取决于被弱引用的对象是否还与其他强引用对象关联）
     *
     * 个人理解：当某个 LinkedHashMapCache 强引用对象没有被其他对象（除了这里）引用时，我们应该让这个对象被回收，
     * 但是由于这里使用的也是强引用，这个对象被其他强引用对象关联了，不可能被回收，存在内存溢出的危险，
     * 所以这里使用了弱引用对象，如果被弱引用的对象没有被其他对象（除了这里）引用时，这个对象会被回收
     *
     * 举个例子：如果我们往一个 Map<Object, Object> 中存放一个key-value键值对
     * 假设对应的键已经不再使用被回收了，那我们无法再获取到对应的值，也无法被回收，占有一定的内存，存在风险
     */
    static LinkedList<WeakReference<LinkedHashMapCache>> linkedHashMapCaches = new LinkedList<>();

    static {
        // 创建一个线程池，1个核心线程
        ScheduledExecutorService executorService = JetCacheExecutor.defaultExecutor();
        // 起一个循环任务一直清理 linkedHashMapCaches 过期的数据（每隔60秒）
        executorService.scheduleWithFixedDelay(() -> run(), 60, 60, TimeUnit.SECONDS);
    }

    static void add(LinkedHashMapCache cache) {
        synchronized (linkedHashMapCaches) {
            // 创建一个弱引用对象，并添加到清理对象中
            linkedHashMapCaches.add(new WeakReference<>(cache));
        }
    }

    static void run() {
        synchronized (linkedHashMapCaches) {
            Iterator<WeakReference<LinkedHashMapCache>> it = linkedHashMapCaches.iterator();
            while (it.hasNext()) {
                WeakReference<LinkedHashMapCache> ref = it.next();
                // 获取被弱引用的对象（强引用）
                LinkedHashMapCache c = ref.get();
                if (c == null) { // 表示被弱引用的对象被标记成了垃圾，则移除
                    it.remove();
                } else {
                    c.cleanExpiredEntry();
                }
            }
        }
    }
}

public class CaffeineCache<K, V> extends AbstractEmbeddedCache<K, V> {

    /**
     * 缓存实例对象
     */
    private com.github.benmanes.caffeine.cache.Cache cache;

    public CaffeineCache(EmbeddedCacheConfig<K, V> config) {
        super(config);
    }

    /**
     * 初始化本地缓存的容器
     *
     * @return Map对象
     */
    @Override
    @SuppressWarnings("unchecked")
    protected InnerMap createAreaCache() {
        Caffeine<Object, Object> builder = Caffeine.newBuilder();
        // 设置缓存实例的最大缓存数量
        builder.maximumSize(config.getLimit());
        final boolean isExpireAfterAccess = config.isExpireAfterAccess();
        final long expireAfterAccess = config.getExpireAfterAccessInMillis();
        // 设置缓存实例的缓存数据的失效策略
        builder.expireAfter(new Expiry<Object, CacheValueHolder>() {
            /**
             * 获取缓存的有效时间
             *
             * @param value 缓存数据
             * @return 有效时间
             */
            private long getRestTimeInNanos(CacheValueHolder value) {
                long now = System.currentTimeMillis();
                long ttl = value.getExpireTime() - now;
                /*
                 * 如果本地缓存设置了多长时间没访问缓存则失效
                 */
                if(isExpireAfterAccess){
                    // 设置缓存的失效时间
                    // 多长时间没访问缓存则失效 and 缓存的有效时长取 min
                    ttl = Math.min(ttl, expireAfterAccess);
                }
                return TimeUnit.MILLISECONDS.toNanos(ttl);
            }

            @Override
            public long expireAfterCreate(Object key, CacheValueHolder value, long currentTime) {
                return getRestTimeInNanos(value);
            }

            @Override
            public long expireAfterUpdate(Object key, CacheValueHolder value,
                                          long currentTime, long currentDuration) {
                return currentDuration;
            }

            @Override
            public long expireAfterRead(Object key, CacheValueHolder value,
                                        long currentTime, long currentDuration) {
                return getRestTimeInNanos(value);
            }
        });
        // 构建 Cache 缓存实例
        cache = builder.build();
        return new InnerMap() {
            @Override
            public Object getValue(Object key) {
                return cache.getIfPresent(key);
            }

            @Override
            public Map getAllValues(Collection keys) {
                return cache.getAllPresent(keys);
            }

            @Override
            public void putValue(Object key, Object value) {
                cache.put(key, value);
            }

            @Override
            public void putAllValues(Map map) {
                cache.putAll(map);
            }

            @Override
            public boolean removeValue(Object key) {
                return cache.asMap().remove(key) != null;
            }

            @Override
            public void removeAllValues(Collection keys) {
                cache.invalidateAll(keys);
            }

            @Override
            public boolean putIfAbsentValue(Object key, Object value) {
                return cache.asMap().putIfAbsent(key, value) == null;
            }
        };
    }
}

public class MultiLevelCache<K, V> extends AbstractCache<K, V> {

    private Cache[] caches;

    private MultiLevelCacheConfig<K, V> config;

    @SuppressWarnings("unchecked")
    @Deprecated
    public MultiLevelCache(Cache... caches) throws CacheConfigException {
        this.caches = caches;
        checkCaches();
        CacheConfig lastConfig = caches[caches.length - 1].config();
        config = new MultiLevelCacheConfig<>();
        config.setCaches(Arrays.asList(caches));
        config.setExpireAfterWriteInMillis(lastConfig.getExpireAfterWriteInMillis());
        config.setCacheNullValue(lastConfig.isCacheNullValue());
    }

    @SuppressWarnings("unchecked")
    public MultiLevelCache(MultiLevelCacheConfig<K, V> cacheConfig) throws CacheConfigException {
        this.config = cacheConfig;
        this.caches = cacheConfig.getCaches().toArray(new Cache[]{});
        checkCaches();
    }

    private void checkCaches() {
        if (caches == null || caches.length == 0) {
            throw new IllegalArgumentException();
        }
        for (Cache c : caches) {
            if (c.config().getLoader() != null) {
                throw new CacheConfigException("Loader on sub cache is not allowed, set the loader into MultiLevelCache.");
            }
        }
    }

    public Cache[] caches() {
        return caches;
    }

    @Override
    public MultiLevelCacheConfig<K, V> config() {
        return config;
    }

    @Override
    public CacheResult PUT(K key, V value) {
        if (config.isUseExpireOfSubCache()) { // 本地缓存使用自己的失效时间
            // 设置了TimeUnit为null，本地缓存则使用自己的到期时间
            return PUT(key, value, 0, null);
        } else {
            return PUT(key, value, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
        }
    }

    @Override
    public CacheResult PUT_ALL(Map<? extends K, ? extends V> map) {
        if (config.isUseExpireOfSubCache()) {
            return PUT_ALL(map, 0, null);
        } else {
            return PUT_ALL(map, config().getExpireAfterWriteInMillis(), TimeUnit.MILLISECONDS);
        }
    }

    @Override
    protected CacheGetResult<V> do_GET(K key) {
    	// 遍历多级缓存（远程缓存排在后面）
        for (int i = 0; i < caches.length; i++) {
            Cache cache = caches[i];
            CacheGetResult result = cache.GET(key);
            if (result.isSuccess()) {
                CacheValueHolder<V> holder = unwrapHolder(result.getHolder());
                /*
                 * 这个遍历是从低层的缓存开始获取，获取成功则将该值设置到更低层的缓存中
                 * 情景：
                 * 本地没有获取到缓存，远程获取到了缓存，这里会将远程的缓存数据设置到本地中，
                 * 这样下次请求则直接从本次获取，减少了远程获取的时间
                 */
                checkResultAndFillUpperCache(key, i, holder);
                return new CacheGetResult(CacheResultCode.SUCCESS, null, holder);
            }
        }
        return CacheGetResult.NOT_EXISTS_WITHOUT_MSG;
    }

    private CacheValueHolder<V> unwrapHolder(CacheValueHolder<V> h) {
        // if @Cached or @CacheCache change type from REMOTE to BOTH (or from BOTH to REMOTE),
        // during the dev/publish process, the value type which different application server put into cache server will be different
        // (CacheValueHolder<V> and CacheValueHolder<CacheValueHolder<V>>, respectively).
        // So we need correct the problem at here and in CacheGetResult.
        Objects.requireNonNull(h);
        if (h.getValue() instanceof CacheValueHolder) {
            return (CacheValueHolder<V>) h.getValue();
        } else {
            return h;
        }
    }

    private void checkResultAndFillUpperCache(K key, int i, CacheValueHolder<V> h) {
        Objects.requireNonNull(h);
        long currentExpire = h.getExpireTime();
        long now = System.currentTimeMillis();
        if (now <= currentExpire) {
            if(config.isUseExpireOfSubCache()){ // 如果使用本地自己的缓存过期时间
                // 使用本地缓存自己的过期时间
                PUT_caches(i, key, h.getValue(), 0, null);
            } else { // 使用远程缓存的过期时间
                long restTtl = currentExpire - now;
                if (restTtl > 0) { // 远程缓存数据还未失效，则重新设置本地的缓存
                    PUT_caches(i, key, h.getValue(), restTtl, TimeUnit.MILLISECONDS);
                }
            }
        }
    }

    @Override
    protected MultiGetResult<K, V> do_GET_ALL(Set<? extends K> keys) {
        HashMap<K, CacheGetResult<V>> resultMap = new HashMap<>();
        Set<K> restKeys = new HashSet<>(keys);
        for (int i = 0; i < caches.length; i++) {
            if (restKeys.size() == 0) {
                break;
            }
            Cache<K, CacheValueHolder<V>> c = caches[i];
            MultiGetResult<K, CacheValueHolder<V>> allResult = c.GET_ALL(restKeys);
            if (allResult.isSuccess() && allResult.getValues() != null) {
                for (Map.Entry<K, CacheGetResult<CacheValueHolder<V>>> en : allResult.getValues().entrySet()) {
                    K key = en.getKey();
                    CacheGetResult result = en.getValue();
                    if (result.isSuccess()) {
                        CacheValueHolder<V> holder = unwrapHolder(result.getHolder());
                        checkResultAndFillUpperCache(key, i, holder);
                        resultMap.put(key, new CacheGetResult(CacheResultCode.SUCCESS, null, holder));
                        restKeys.remove(key);
                    }
                }
            }
        }
        for (K k : restKeys) {
            resultMap.put(k, CacheGetResult.NOT_EXISTS_WITHOUT_MSG);
        }
        return new MultiGetResult<>(CacheResultCode.SUCCESS, null, resultMap);
    }

    @Override
    protected CacheResult do_PUT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
        return PUT_caches(caches.length, key, value, expireAfterWrite, timeUnit);
    }

    @Override
    protected CacheResult do_PUT_ALL(Map<? extends K, ? extends V> map, long expireAfterWrite, TimeUnit timeUnit) {
        CompletableFuture<ResultData> future = CompletableFuture.completedFuture(null);
        for (Cache c : caches) {
            CacheResult r;
            if(timeUnit == null) {
                r = c.PUT_ALL(map);
            } else {
                r = c.PUT_ALL(map, expireAfterWrite, timeUnit);
            }
            future = combine(future, r);
        }
        return new CacheResult(future);
    }

    private CacheResult PUT_caches(int lastIndex, K key, V value, long expire, TimeUnit timeUnit) {
        CompletableFuture<ResultData> future = CompletableFuture.completedFuture(null);
        for (int i = 0; i < lastIndex; i++) {
            Cache cache = caches[i];
            CacheResult r;
            if (timeUnit == null) { // 表示本地缓存使用自己过期时间
                r = cache.PUT(key, value);
            } else {
                r = cache.PUT(key, value, expire, timeUnit);
            }
            // 将多个 PUT 操作放在一条链上
            future = combine(future, r);
        }
        return new CacheResult(future);
    }

    private CompletableFuture<ResultData> combine(CompletableFuture<ResultData> future, CacheResult result) {
        return future.thenCombine(result.future(), (d1, d2) -> {
            if (d1 == null) {
                return d2;
            }
            if (d1.getResultCode() != d2.getResultCode()) {
                return new ResultData(CacheResultCode.PART_SUCCESS, null, null);
            }
            return d1;
        });
    }

    @Override
    protected CacheResult do_REMOVE(K key) {
        CompletableFuture<ResultData> future = CompletableFuture.completedFuture(null);
        for (Cache cache : caches) {
            CacheResult r = cache.REMOVE(key);
            future = combine(future, r);
        }
        return new CacheResult(future);
    }

    @Override
    protected CacheResult do_REMOVE_ALL(Set<? extends K> keys) {
        CompletableFuture<ResultData> future = CompletableFuture.completedFuture(null);
        for (Cache cache : caches) {
            CacheResult r = cache.REMOVE_ALL(keys);
            future = combine(future, r);
        }
        return new CacheResult(future);
    }

    @Override
    public <T> T unwrap(Class<T> clazz) {
        Objects.requireNonNull(clazz);
        for (Cache cache : caches) {
            try {
                T obj = (T) cache.unwrap(clazz);
                if (obj != null) {
                    return obj;
                }
            } catch (IllegalArgumentException e) {
                // ignore
            }
        }
        throw new IllegalArgumentException(clazz.getName());
    }

    @Override
    public AutoReleaseLock tryLock(K key, long expire, TimeUnit timeUnit) {
        if (key == null) {
            return null;
        }
        return caches[caches.length - 1].tryLock(key, expire, timeUnit);
    }

    @Override
    public boolean putIfAbsent(K key, V value) {
        throw new UnsupportedOperationException("putIfAbsent is not supported by MultiLevelCache");
    }

    @Override
    protected CacheResult do_PUT_IF_ABSENT(K key, V value, long expireAfterWrite, TimeUnit timeUnit) {
        throw new UnsupportedOperationException("PUT_IF_ABSENT is not supported by MultiLevelCache");
    }

    @Override
    public void close() {
        for (Cache c : caches) {
            c.close();
        }
    }
}

public class RefreshCache<K, V> extends LoadingCache<K, V> {
    
    protected CacheConfig<K, V> config;
    
    /**
	 * 用于保存刷新任务
	 */
	private ConcurrentHashMap<Object, RefreshTask> taskMap = new ConcurrentHashMap<>();
    
    protected void addOrUpdateRefreshTask(K key, CacheLoader<K, V> loader) {
		// 获取缓存刷新策略
		RefreshPolicy refreshPolicy = config.getRefreshPolicy();
		if (refreshPolicy == null) { // 没有则不进行刷新
			return;
		}
		// 获取刷新时间间隔
		long refreshMillis = refreshPolicy.getRefreshMillis();
		if (refreshMillis > 0) {
			// 获取线程任务的ID
			Object taskId = getTaskId(key);
			// 获取对应的RefreshTask，不存在则创建一个
			RefreshTask refreshTask = taskMap.computeIfAbsent(taskId, tid -> {
				logger.debug("add refresh task. interval={},  key={}", refreshMillis, key);
				RefreshTask task = new RefreshTask(taskId, key, loader);
				task.lastAccessTime = System.currentTimeMillis();
				/*
				 * 获取 ScheduledExecutorService 周期/延迟线程池，10个核心线程，创建的线程都是守护线程
				 * scheduleWithFixedDelay(Runnable command, long initialDelay, long period, TimeUnit unit)
				 * 运行的任务task、多久延迟后开始执行、后续执行的周期间隔多长，时间单位
				 * 通过其创建一个循环任务，用于刷新缓存数据
				 */
				ScheduledFuture<?> future = JetCacheExecutor.heavyIOExecutor().scheduleWithFixedDelay(task,
						refreshMillis, refreshMillis, TimeUnit.MILLISECONDS);
				task.future = future;
				return task;
			});
			// 设置最后一次访问时间
			refreshTask.lastAccessTime = System.currentTimeMillis();
		}
	}
}

public class RefreshCache<K, V> extends LoadingCache<K, V> {
    
    protected Cache concreteCache() {
		Cache c = getTargetCache();
		while (true) {
			if (c instanceof ProxyCache) {
				c = ((ProxyCache) c).getTargetCache();
			} else if (c instanceof MultiLevelCache) {
				Cache[] caches = ((MultiLevelCache) c).caches();
				// 如果是两级缓存则返回远程缓存
				c = caches[caches.length - 1];
			} else {
				return c;
			}
		}
	}
    
    class RefreshTask implements Runnable {
		/**
		 * 唯一标志符，也就是Key转换后的值
		 */
		private Object taskId;
		/**
		 * 缓存的Key
		 */
		private K key;
		/**
		 * 执行方法的CacheLoader对象
		 */
		private CacheLoader<K, V> loader;

		/**
		 * 最后一次访问时间
		 */
		private long lastAccessTime;
		/**
		 * 该 Task 的执行策略
		 */
		private ScheduledFuture future;

		RefreshTask(Object taskId, K key, CacheLoader<K, V> loader) {
			this.taskId = taskId;
			this.key = key;
			this.loader = loader;
		}

		private void cancel() {
			logger.debug("cancel refresh: {}", key);
			// 尝试中断当前任务
			future.cancel(false);
			// 从任务列表中删除
			taskMap.remove(taskId);
		}

		/**
		 * 重新加载数据
		 *
		 * @throws Throwable 异常
		 */
		private void load() throws Throwable {
			CacheLoader<K, V> l = loader == null ? config.getLoader() : loader;
			if (l != null) {
				// 封装 CacheLoader 成 ProxyLoader，加载后会发起 Load 事件
				l = CacheUtil.createProxyLoader(cache, l, eventConsumer);
				// 加载
				V v = l.load(key);
				if (needUpdate(v, l)) {
					// 将重新加载的数据放入缓存
					cache.PUT(key, v);
				}
			}
		}

		/**
		 * 远程加载数据
		 *
		 * @param concreteCache 缓存对象
		 * @param currentTime   当前时间
		 * @throws Throwable 异常
		 */
		private void externalLoad(final Cache concreteCache, final long currentTime) throws Throwable {
			// 获取 Key 转换后的值
			byte[] newKey = ((AbstractExternalCache) concreteCache).buildKey(key);
			// 创建分布式锁对应的Key
			byte[] lockKey = combine(newKey, "_#RL#".getBytes());
			// 分布式锁的存在时间
			long loadTimeOut = RefreshCache.this.config.getRefreshPolicy().getRefreshLockTimeoutMillis();
			// 刷新间隔
			long refreshMillis = config.getRefreshPolicy().getRefreshMillis();
			// Key对应的时间戳Key（用于存放上次刷新时间）
			byte[] timestampKey = combine(newKey, "_#TS#".getBytes());

			// AbstractExternalCache buildKey method will not convert byte[]
			// 获取Key上一次刷新时间
			CacheGetResult refreshTimeResult = concreteCache.GET(timestampKey);
			boolean shouldLoad = false; // 是否需要重新加载
			if (refreshTimeResult.isSuccess()) {
				// 当前时间与上一次刷新的时间间隔是否大于或等于刷新间隔
				shouldLoad = currentTime >= Long.parseLong(refreshTimeResult.getValue().toString()) + refreshMillis;
			} else if (refreshTimeResult.getResultCode() == CacheResultCode.NOT_EXISTS) { // 无缓存
				shouldLoad = true;
			}

			if (!shouldLoad) {
				if (multiLevelCache) {
					// 将顶层的缓存数据更新至低层的缓存中，例如将远程的缓存数据放入本地缓存
					// 因为如果是多级缓存，创建刷新任务后，我们只需更新远程的缓存，然后从远程缓存获取缓存数据更新低层的缓存，保证缓存一致
					refreshUpperCaches(key);
				}
				return;
			}

			// 重新加载
			Runnable r = () -> {
				try {
					load();
					// AbstractExternalCache buildKey method will not convert byte[]
					// 保存一个key-value至redis，其中的信息为该value的生成时间，刷新缓存
					concreteCache.put(timestampKey, String.valueOf(System.currentTimeMillis()));
				} catch (Throwable e) {
					throw new CacheException("refresh error", e);
				}
			};

			// AbstractExternalCache buildKey method will not convert byte[]
			// 分布式缓存没有一个全局分配的功能，这里尝试获取一把非严格的分布式锁，获取锁的超时时间默认60秒，也就是获取到这把锁最多可以拥有60秒
			// 只有获取Key对应的这把分布式锁，才执行重新加载的操作
			boolean lockSuccess = concreteCache.tryLockAndRun(lockKey, loadTimeOut, TimeUnit.MILLISECONDS, r);
			if (!lockSuccess && multiLevelCache) { // 没有获取到锁并且是多级缓存
				// 这个时候应该有其他实例在刷新缓存，所以这里设置过一会直接获取远程的缓存数据更新到本地
				// 创建一个延迟任务（1/5刷新间隔后），将最顶层的缓存数据更新至每一层
				JetCacheExecutor.heavyIOExecutor().schedule(() -> refreshUpperCaches(key), (long) (0.2 * refreshMillis),
						TimeUnit.MILLISECONDS);
			}
		}

		private void refreshUpperCaches(K key) {
			MultiLevelCache<K, V> targetCache = (MultiLevelCache<K, V>) getTargetCache();
			Cache[] caches = targetCache.caches();
			int len = caches.length;

			// 获取多级缓存中顶层的缓存数据
			CacheGetResult cacheGetResult = caches[len - 1].GET(key);
			if (!cacheGetResult.isSuccess()) {
				return;
			}
			// 将缓存数据重新放入低层缓存
			for (int i = 0; i < len - 1; i++) {
				caches[i].PUT(key, cacheGetResult.getValue());
			}
		}

		/**
		 * 刷新任务的具体执行
		 */
		@Override
		public void run() {
			try {
				if (config.getRefreshPolicy() == null || (loader == null && !hasLoader())) {
					// 取消执行
					cancel();
					return;
				}
				long now = System.currentTimeMillis();
				long stopRefreshAfterLastAccessMillis = config.getRefreshPolicy().getStopRefreshAfterLastAccessMillis();
				if (stopRefreshAfterLastAccessMillis > 0) {
					// 最后一次访问到现在时间的间隔超过了设置的 stopRefreshAfterLastAccessMillis，则取消当前任务执行
					if (lastAccessTime + stopRefreshAfterLastAccessMillis < now) {
						logger.debug("cancel refresh: {}", key);
						cancel();
						return;
					}
				}
				logger.debug("refresh key: {}", key);
				// 获取缓存实例对象，如果是多层则返回顶层，也就是远程缓存
				Cache concreteCache = concreteCache();
				if (concreteCache instanceof AbstractExternalCache) { // 远程缓存刷新
					externalLoad(concreteCache, now);
				} else { // 本地缓存刷新
					load();
				}
			} catch (Throwable e) {
				logger.error("refresh error: key=" + key, e);
			}
		}
	}
}

public abstract class AbstractCacheAutoInit implements InitializingBean {

    @Autowired
    protected ConfigurableEnvironment environment;

    @Autowired
    protected AutoConfigureBeans autoConfigureBeans;

    @Autowired
    protected ConfigProvider configProvider;

    protected String[] typeNames;

    private boolean inited = false;

    public AbstractCacheAutoInit(String... cacheTypes) {
        Objects.requireNonNull(cacheTypes,"cacheTypes can't be null");
        Assert.isTrue(cacheTypes.length > 0, "cacheTypes length is 0");
        this.typeNames = cacheTypes;
    }

    /**
     * 初始化方法
     */
    @Override
    public void afterPropertiesSet() {
        if (!inited) {
            synchronized (this) {
                if (!inited) {
                    // 这里我们有两个指定前缀 'jetcache.local' 'jetcache.remote'
                    process("jetcache.local.", autoConfigureBeans.getLocalCacheBuilders(), true);
                    process("jetcache.remote.", autoConfigureBeans.getRemoteCacheBuilders(), false);
                    inited = true;
                }
            }
        }
    }

    private void process(String prefix, Map cacheBuilders, boolean local) {
        // 创建一个配置对象（本地或者远程）
        ConfigTree resolver = new ConfigTree(environment, prefix);
        // 获取本地或者远程的配置项
        Map<String, Object> m = resolver.getProperties();
        // 获取本地或者远程的 area ，这里我一般只有默认的 default
        Set<String> cacheAreaNames = resolver.directChildrenKeys();
        for (String cacheArea : cacheAreaNames) {
            // 获取本地或者远程存储类型，例如 caffeine，redis.lettuce
            final Object configType = m.get(cacheArea + ".type");
            // 缓存类型是否和当前 CacheAutoInit 的某一个 typeName 匹配（不同的 CacheAutoInit 会设置一个或者多个 typename）
            boolean match = Arrays.stream(typeNames).anyMatch((tn) -> tn.equals(configType));
            /*
             * 因为有很多 CacheAutoInit 继承者，都会执行这个方法，不同的继承者解析不同的配置
             * 例如 CaffeineAutoConfiguration 只解析 jetcache.local.default.type=caffeine 即可
             * RedisLettuceAutoInit 只解析 jetcache.remote.default.type=redis.lettuce 即可
             */
            if (!match) {
                continue;
            }
            // 获取本地或者远程的 area 的子配置项
            ConfigTree ct = resolver.subTree(cacheArea + ".");
            logger.info("init cache area {} , type= {}", cacheArea, typeNames[0]);
            // 根据配置信息构建本地或者远程缓存的 CacheBuilder 构造器
            CacheBuilder c = initCache(ct, local ? "local." + cacheArea : "remote." + cacheArea);
            // 将 CacheBuilder 构造器存放至 AutoConfigureBeans
            cacheBuilders.put(cacheArea, c);
        }
    }

    /**
     * 设置公共的配置到 CacheBuilder 构造器中
     *
     * @param builder 构造器
     * @param ct      配置信息
     */
    protected void parseGeneralConfig(CacheBuilder builder, ConfigTree ct) {
        AbstractCacheBuilder acb = (AbstractCacheBuilder) builder;
        // 设置 Key 的转换函数
        acb.keyConvertor(configProvider.parseKeyConvertor(ct.getProperty("keyConvertor")));
        // 设置超时时间
        String expireAfterWriteInMillis = ct.getProperty("expireAfterWriteInMillis");
        if (expireAfterWriteInMillis == null) {
            // compatible with 2.1 兼容老版本
            expireAfterWriteInMillis = ct.getProperty("defaultExpireInMillis");
        }
        if (expireAfterWriteInMillis != null) {
            acb.setExpireAfterWriteInMillis(Long.parseLong(expireAfterWriteInMillis));
        }
        // 多长时间没有访问就让缓存失效，0表示不使用该功能（注意：只支持本地缓存）
        String expireAfterAccessInMillis = ct.getProperty("expireAfterAccessInMillis");
        if (expireAfterAccessInMillis != null) {
            acb.setExpireAfterAccessInMillis(Long.parseLong(expireAfterAccessInMillis));
        }
    }

    /**
     * 初始化 CacheBuilder 构造器交由子类去实现
     *
     * @param ct                  配置信息
     * @param cacheAreaWithPrefix 配置前缀
     * @return CacheBuilder 构造器
     */
    protected abstract CacheBuilder initCache(ConfigTree ct, String cacheAreaWithPrefix);
}

public abstract class EmbeddedCacheAutoInit extends AbstractCacheAutoInit {

    public EmbeddedCacheAutoInit(String... cacheTypes) {
        super(cacheTypes);
    }

    @Override
    protected void parseGeneralConfig(CacheBuilder builder, ConfigTree ct) {
        super.parseGeneralConfig(builder, ct);
        EmbeddedCacheBuilder ecb = (EmbeddedCacheBuilder) builder;
        // 设置本地缓存每个缓存实例的缓存数量个数限制（默认100）
        ecb.limit(Integer.parseInt(ct.getProperty("limit", String.valueOf(CacheConsts.DEFAULT_LOCAL_LIMIT))));
    }
}

@Component
@Conditional(LinkedHashMapAutoConfiguration.LinkedHashMapCondition.class)
public class LinkedHashMapAutoConfiguration extends EmbeddedCacheAutoInit {
    public LinkedHashMapAutoConfiguration() {
        super("linkedhashmap");
    }

    @Override
    protected CacheBuilder initCache(ConfigTree ct, String cacheAreaWithPrefix) {
        // 创建一个 LinkedHashMapCacheBuilder 构造器
        LinkedHashMapCacheBuilder builder = LinkedHashMapCacheBuilder.createLinkedHashMapCacheBuilder();
        // 解析相关配置至 LinkedHashMapCacheBuilder 的 CacheConfig 中
        parseGeneralConfig(builder, ct);
        return builder;
    }

    public static class LinkedHashMapCondition extends JetCacheCondition {
        // 配置了缓存类型为 linkedhashmap 当前类才会被注入 Spring 容器
        public LinkedHashMapCondition() {
            super("linkedhashmap");
        }
    }
}

@Component
@Conditional(CaffeineAutoConfiguration.CaffeineCondition.class)
public class CaffeineAutoConfiguration extends EmbeddedCacheAutoInit {
    public CaffeineAutoConfiguration() {
        super("caffeine");
    }

    @Override
    protected CacheBuilder initCache(ConfigTree ct, String cacheAreaWithPrefix) {
        // 创建一个 CaffeineCacheBuilder 构造器
        CaffeineCacheBuilder builder = CaffeineCacheBuilder.createCaffeineCacheBuilder();
        // 解析相关配置至 CaffeineCacheBuilder 的 CacheConfig 中
        parseGeneralConfig(builder, ct);
        return builder;
    }

    public static class CaffeineCondition extends JetCacheCondition {
        // 配置了缓存类型为 caffeine 当前类才会被注入 Spring 容器
        public CaffeineCondition() {
            super("caffeine");
        }
    }
}

public abstract class ExternalCacheAutoInit extends AbstractCacheAutoInit {
    public ExternalCacheAutoInit(String... cacheTypes) {
        super(cacheTypes);
    }

    /**
     * 设置远程缓存 CacheBuilder 构造器的相关配置
     *
     * @param builder 构造器
     * @param ct      配置信息
     */
    @Override
    protected void parseGeneralConfig(CacheBuilder builder, ConfigTree ct) {
        super.parseGeneralConfig(builder, ct);
        ExternalCacheBuilder ecb = (ExternalCacheBuilder) builder;
        // 设置远程缓存 key 的前缀
        ecb.setKeyPrefix(ct.getProperty("keyPrefix"));
        /*
         * 根据配置创建缓存数据的编码函数和解码函数
         */
        ecb.setValueEncoder(configProvider.parseValueEncoder(ct.getProperty("valueEncoder", CacheConsts.DEFAULT_SERIAL_POLICY)));
        ecb.setValueDecoder(configProvider.parseValueDecoder(ct.getProperty("valueDecoder", CacheConsts.DEFAULT_SERIAL_POLICY)));
    }
}

@Configuration
@Conditional(RedisAutoConfiguration.RedisCondition.class)
public class RedisAutoConfiguration {

    public static final String AUTO_INIT_BEAN_NAME = "redisAutoInit";

    @Bean(name = AUTO_INIT_BEAN_NAME)
    public RedisAutoInit redisAutoInit() {
        return new RedisAutoInit();
    }

    public static class RedisCondition extends JetCacheCondition {
        // 配置了缓存类型为 redis 当前类才会被注入 Spring 容器
        public RedisCondition() {
            super("redis");
        }
    }

    public static class RedisAutoInit extends ExternalCacheAutoInit {
        public RedisAutoInit() {
            // 设置缓存类型
            super("redis");
        }

        @Autowired
        private AutoConfigureBeans autoConfigureBeans;

        @Override
        protected CacheBuilder initCache(ConfigTree ct, String cacheAreaWithPrefix) {
            Pool jedisPool = parsePool(ct);
            Pool[] slavesPool = null;
            int[] slavesPoolWeights = null;
            // 是否只从 Redis 的从节点读取数据
            boolean readFromSlave = Boolean.parseBoolean(ct.getProperty("readFromSlave", "False"));
            // 获取从节点的配置信息
            ConfigTree slaves = ct.subTree("slaves.");
            Set<String> slaveNames = slaves.directChildrenKeys();
            // 依次创建每个从节点的连接池
            if (slaveNames.size() > 0) {
                slavesPool = new Pool[slaveNames.size()];
                slavesPoolWeights = new int[slaveNames.size()];
                int i = 0;
                for (String slaveName: slaveNames) {
                    ConfigTree slaveConfig = slaves.subTree(slaveName + ".");
                    slavesPool[i] = parsePool(slaveConfig);
                    slavesPoolWeights[i] = Integer.parseInt(slaveConfig.getProperty("weight","100"));
                    i++;
                }
            }

            // 创建一个 RedisCacheBuilder 构造器
            ExternalCacheBuilder externalCacheBuilder = RedisCacheBuilder.createRedisCacheBuilder()
                    .jedisPool(jedisPool)
                    .readFromSlave(readFromSlave)
                    .jedisSlavePools(slavesPool)
                    .slaveReadWeights(slavesPoolWeights);

            // 解析相关配置至 RedisCacheBuilder 的 CacheConfig 中
            parseGeneralConfig(externalCacheBuilder, ct);

            // eg: "jedisPool.remote.default"
            autoConfigureBeans.getCustomContainer().put("jedisPool." + cacheAreaWithPrefix, jedisPool);

            return externalCacheBuilder;
        }

        /**
         * 创建 Redis 连接池
         *
         * @param ct 配置信息
         * @return 连接池
         */
        private Pool<Jedis> parsePool(ConfigTree ct) {
            // 创建连接池配置对象
            GenericObjectPoolConfig poolConfig = parsePoolConfig(ct);

            String host = ct.getProperty("host", (String) null);
            int port = Integer.parseInt(ct.getProperty("port", "0"));
            int timeout = Integer.parseInt(ct.getProperty("timeout", String.valueOf(Protocol.DEFAULT_TIMEOUT)));
            String password = ct.getProperty("password", (String) null);
            int database = Integer.parseInt(ct.getProperty("database", String.valueOf(Protocol.DEFAULT_DATABASE)));
            String clientName = ct.getProperty("clientName", (String) null);
            boolean ssl = Boolean.parseBoolean(ct.getProperty("ssl", "false"));

            String masterName = ct.getProperty("masterName", (String) null);
            String sentinels = ct.getProperty("sentinels", (String) null);//ip1:port,ip2:port

            Pool<Jedis> jedisPool;
            if (sentinels == null) {
                Objects.requireNonNull(host, "host/port or sentinels/masterName is required");
                if (port == 0) {
                    throw new IllegalStateException("host/port or sentinels/masterName is required");
                }
                // 创建一个 Jedis 连接池
                jedisPool = new JedisPool(poolConfig, host, port, timeout, password, database, clientName, ssl);
            } else {
                Objects.requireNonNull(masterName, "host/port or sentinels/masterName is required");
                String[] strings = sentinels.split(",");
                HashSet<String> sentinelsSet = new HashSet<>();
                for (String s : strings) {
                    if (s != null && !s.trim().equals("")) {
                        sentinelsSet.add(s.trim());
                    }
                }
                // 创建一个 Jedis Sentine 连接池
                jedisPool = new JedisSentinelPool(masterName, sentinelsSet, poolConfig, timeout, password, database, clientName);
            }
            return jedisPool;
        }
    }
}