A marker used to denote that the class should be pre-loaded into hibernate's
class mapping. Used for component classes which are not going to be mapped to
the RDBMS but which must be loadable for mapped classes to instantiate
correctly. Basically if you refer to a class that isn't itself going to be
mapped in hibernate within a mapping definition you'll need to add that
component class to this SPI or hibernate won't be able to find it as it won't
know that it should associate it with the appropriate class loader.
This should be used as an SPI marker, and set as the first SPI registry in
the preloadRegistries property of the SpiRegistryAwareLocalSessionFactoryBean