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Container-Managed Persistence in Borland Enterprise Server
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Mapping one field to multiple columns
Many users may employ coarse-grained entity beans that implement a Java class to
represent more fine-grained data. For example, an entity bean might use an Address
class as a field, but may need to map elements of the class (like AddressLine1,
AddressCity, and so forth) to an underlying database. To do this, you use the
element, which defines a field map between your fine-grained class and its
underlying database representation. Note that such classes must implement
java.io.Serializable and all their data members must be public.
Consider an entity bean called Customer that uses the class Address to represent a
customer's address. The Address class has fields for AddressLine, AddressCity,
AddressState, and AddressZip. Using the following XML, we can map the class to its
representation in a database with corresponding columns:
Customer
.
.
Address
Address.AddressLine
STREET
Address.AddressCity
CITY
Address.AddressState
STATE
Address.AddressZip
ZIP
.
.
Note that we use one element per database column.
134 BES Developer’s Guide