This defines a kind of listener method which will be called whenever a cache miss occurs.
In other words, if the cache is asked to retrieve an object by a key which does not exist
in the cache then this method will be called if defined for that cache. Then the returned
value will be returned from the lookup (or a null if no new value was found) and
also inserted into the cache (unless the value was null) WARNING: This can make your cache misses very costly so you will want to be careful
about what you make this method actually do
Similar to https://github.com/jsr107/jsr107spec/blob/master/src/main/java/javax/cache/integration/CacheLoader.java
Aligns with JSR-107 CacheLoader
Send questions to Aaron Zeckoski
Loads an object. Application developers should implement this
method to customize the loading of a value for a cache entry. This method
is called by a cache when a requested entry is not in the cache. If
the object can't be loaded null should be returned.
key - the key identifying the object being loaded
The value for the entry that is to be stored in the cache or
null if the object can't be loaded
Loads multiple objects. Application developers should implement this
method to customize the loading of cache entries. This method is called
when the requested object is not in the cache. If an object can't be loaded,
it is not returned in the resulting map.