jetcache-core/src/main/java/com/alicp/jetcache/support/BroadcastManager.java
jetcache-core/src/main/java/com/alicp/jetcache/CacheMonitor.java
JCache规范不支持null,所以cache2k默认也不支持,不过可以通过permitNullValues(true)来开启,这样子缓存就可以存储null值