The current implementation has the following
limitations with collections:
- Only List, Set and Map are supported. Also it should be noted that the Java Collection API does not
fully describe the behavior of implementations, so the cache versions may differ slightly from the common Java implementations (e.g. handling of NULL)
- As of PojoCache 2.0, HashMap keys must be serializable.
Prior to PojoCache 2.0, HashMap keys were converted to String.
This was fixed as you couldn't get the key back in its original form. See issue JBCACHE-399 for more details.