Oracle JHeadstart Developer's Guide - Downloads - Oracle

Suggestion: If all primary key attributes have the same name, for example Id,
retrieving sequence values from the database in the create method is
something you could implement in your BC base classes. By doing so, you do
not need to implement a create method for each entity object. In the EO base
class you can retrieve from one sequence that is used for all Entity Objects. Or
you can implement a more sophisticated mechanism that derives the sequence
name from the Entity Object name.
3.2.4.2. Surrogate Primary Key populated in the database
The database generates the primary key value, so no Java code is needed to populate the
primary key. However, your Business Components Model needs to know that values get
refreshed in the database after the insert.
ADF Developer’s Guide, section 6.6.3.8 “Trigger-Assigned Primary Key
Values”.
http://download-west.oracle.com/docs/html/B25947_01/bcentities006.htm#sm0147
When you plan to create screens that insert a master row and one or more detail rows in
one transaction, you will need to ensure that ADF BC first posts the master row and then
the detail rows, otherwise ADF BC will not be able to set the foreign key of the details
rows correctly. To enforce this posting sequence, you should mark the entity association
as “Composite Association”.
Note that when you mark an association as composite, the detail entity object can only be
created as a detail of the master entity object, which means you cannot create a page that
directly creates detail entity object, in addition to the master-detail page. If you try to do
so, you will get error JBO-25030: Failed to find or invalidate owning entity.
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