Base class for strategies that store their values as keys in the session. Implements a uniform
format for the keys, based on a prefix to identify the particular strategy.
Called after each key is read by
AbstractSessionPersistentFieldStrategy.gatherFieldChanges(String) . This implementation
does nothing, subclasses may override.
Parameters: session - the session from which a value was just read Parameters: attributeName - the name of the attribute used to read a value