Hibernate 5: restore ability to inject "cacheRegionFactory" of LocalSessionFactoryBean

Spring provided a convenience property for "cacheRegionFactory" in the Hibernate 3.x and 4.x packages. The current support for Hibernate 5.x no longer provides this flexibility. This is quite unfortunate, as there are some scenarios where customization of the underlying cache infrastructure is desired, and injection of various Spring-managed dependencies is the natural approach.

Please note that the "hibernate.cache.region.factory_class" property is somewhat misleading: in addition to an implementation class, an actual object instance implementing org.hibernate.cache.spi.RegionFactory is equally valid: please see org.hibernate.cache.internal.RegionFactoryInitiator#initiateService.

At the moment we are using Hibernate 5.1.x, and I have not verified that the approach described below is equally applicable to 5.0.x/5.1.x/5.2.x/5.3.x APIs.

That said, the current workaround I am using is to subclass the hibernate5 LocalSessionFactoryBean as follows:

public class MyLocalSessionFactoryBean extends LocalSessionFactoryBean {

    private RegionFactory regionFactory;

    @Required
    public void setRegionFactory(RegionFactory regionFactory) {
        this.regionFactory = regionFactory;
    }

    @Override
    protected SessionFactory buildSessionFactory(LocalSessionFactoryBuilder sfb) {
        sfb.getProperties().put(AvailableSettings.CACHE_REGION_FACTORY, regionFactory);
        return sfb.buildSessionFactory();
    }
}

(inspired by org.springframework.orm.hibernate5.LocalSessionFactoryBuilder#setMultiTenantConnectionProvider)

If possible (across the range of Hibernate versions currently supported by Spring), it would be nice to have the "cacheRegionFactory" restored for 5.1. A backport to 5.0.x would be a bonus