...
Registries add business logic to the data layer. Rules around when an object should be persistent versus transient, creating domain objects for a specific HttpServletRequest or other such behavior should all reside in the Registry layer. Some registries will be very simplysimple, primarily passing through API calls to the DAO layer and it may seem pointless. The registry layer is VERY important however when considering future development. It keeps the DAOs focused on simply doing data access and consolidates the business logic for a domain in a single location.
...