guava cache 踩坑 ———— 初始化load方法，不能返回null

背景

在使用guava cache 的時候，get的時候，會觸發load加載。
但是如果此時load方法返回null，那麼就會報錯

報錯

Caused by: com.google.common.cache.CacheLoader$InvalidCacheLoadException: CacheLoader returned null for key 10.
        at com.google.common.cache.LocalCache$Segment.getAndRecordStats(LocalCache.java:2463)
        at com.google.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2425)
        at com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2298)
        at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2211)
        at com.google.common.cache.LocalCache.get(LocalCache.java:4154)
        at com.google.common.cache.LocalCache.getOrLoad(LocalCache.java:4158)
        at com.google.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:5147)

原因–源碼

   V getAndRecordStats(
        K key,
        int hash,
        LoadingValueReference<K, V> loadingValueReference,
        ListenableFuture<V> newValue)
        throws ExecutionException {
      V value = null;
      try {
        value = getUninterruptibly(newValue);
        if (value == null) {
          throw new InvalidCacheLoadException("CacheLoader returned null for key " + key + ".");
        }
        statsCounter.recordLoadSuccess(loadingValueReference.elapsedNanos());
        storeLoadedValue(key, hash, loadingValueReference, value);
        return value;
      } finally {
        if (value == null) {
          statsCounter.recordLoadException(loadingValueReference.elapsedNanos());
          removeLoadingValue(key, hash, loadingValueReference);
        }
      }
    }

解決方法

load方法或者loadall方法中，堅決不返回null

改爲