By designating CMP sequence groups for entity beans, you
can prevent certain types of database-related exceptions from occurring
during the run time of your EJB application.
Before you begin
Within each group, you specify the order in which the beans
update your relational database tables.
About this task
Both types of sequence groups must be created after you have
assembled the beans into an EJB module, before installing your application
on the product. If you need to edit sequence groups, you must uninstall
the application, make your changes using the following steps as a
guide, and then reinstall your application.
Note:
If you already
selected or plan to use top-down mapping for mapping your enterprise
beans to back-end data, you do not need to create a sequence group
with an RI_INSERT type. The product does not generate an RI policy
for the database schema that it creates when you select top-down mapping.
Procedure
- Switch to the Java™ EE
perspective.
- In the Enterprise Explorer view, select the desired EJB
module.
- Right click the deployment descriptor, and select .
- On the Overview page of the editor,
go to the EJB CMP Sequence Groups section under
the WebSphere® Extensions
section.
- Click Add.
- Type a name for your sequence group.
- select one of the following values from the list for the
group type designation
- RI_INSERT: for setting a bean persistence sequence to prevent
database referential integrity (RI) violations.
- UPDATE_LOCK: for setting a bean persistence sequence to minimize
exceptions resulting from optimistic concurrency control Why and when
to perform this task.
- In the Available Beans list, highlight
the first bean that you want to place in the group. Click the arrow
pointing toward the Selected beans list. The
bean name is removed from the Available beans list and is displayed
in the Selected beans list. Repeat the previous step until you complete
your sequence group. You must add each bean in the order that you
want the persistence manager to handle it. In the case of delete operations
for an RI_INSERT group, the persistence manager reverses the order
that you designate and deletes the beans and their corresponding database
rows accordingly. If you need to alter the sequence of your group,
select a bean and click the arrow to move the bean one position vertically.
- Close the EJB deployment descriptor editor.
- When prompted, click Yes to indicate
that you want to save changes to the deployment descriptor.
What to do next
See the WebSphere Application
Server documentation for more detailed information about Sequence
Groups for CMP Entity Beans.