While Ehcache is a Java cache, it cannot always store its mappings as Java objects.

The on-heap store is capable of storing cached objects either by reference (where the given key and value references are stored) or by value (where a copy of the given key and value are made and those copies are then stored). All other stores are only capable of storing a byte representation of the key/value pair. See the section Heap Tier for more details.

Serializer and Copier are the abstractions to enable these different storage options.