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Container-Managed Persistence in Borland Enterprise Server
To model the relationship between these two tables, a cross-table must be created. For
example, to create a cross-table that shows employee names and the names of the
projects on which they are working, the element would look like the
following:
EMPLOYEE
EMP_NO
LAST_NAME
PROJ_ID
EMPLOYEE_PROJECTS
EMP_NAME
PROJ_ID
PROJ_ID
PROJ_NAME
PROJECT
PROJ_ID
PROJ_NAME
EMP_NO
Since these are “secondary tables” and therefore have no primary keys, the PROJ_ID
column appears in both column lists. This could also be the common column EMP_NO,
depending upon how you wish to model the data.
Using cascade delete and database cascade delete
Use when you want to remove entity bean objects. When cascade
delete is specified for an object, the container automatically deletes all of that object's
dependent objects. For example you may have a Customer bean which has a one-tomany,
uni-directional relationship to an Address bean. Because an address instance
must be associated to a customer, the container automatically deletes all addresses
related to the customer when you delete the customer.
To specify cascade delete, use the element in the ejb-jar.xml file as
follows:
Customer-Account
Account-Has-Customer
one
Chapter 15: Entity Beans and Table Mapping for CMP 2.0 139