34.9. Accessing a Persistence Service with a Facade
Step one in the design of this subsystem is to define a facade for its services; recall that Facade is a common pattern to provide a unified interface to a subsystem. To begin, an operation is needed to retrieve an object given an OID. But in addition to an OID, the subsystem needs to know what type of object to materialize; therefore, the class type will also be provided. Figure 34.4 illustrates some operations of the facade and its use in collaboration with one of the NextGen service adapters.
Figure 34.4. The PersistenceFacade.
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