About Oracle ADF Associations

Oracle ADF associations are business components that define a relationship between two Oracle ADF entity object definitions (the "source" and "destination" entity objects) based on sets of entity attributes (the "source" and "destination" attributes) from each. These can range from simple one-to-many relationships based on foreign keys to complex many-to-many relationships. For example, associations can represent:

The one-to-many relationship between a customer and all orders placed by that customer
The one-to-one relationship between a product and its extended description (if these are represented by separate entity objects
The many-to-many relationship between products and the warehouses that currently stock them

To create an association, see Representing Foreign Key Relationships.

Associations and Datasources

Associations map to relationships between single objects in the datasource. In the vast majority of cases, these are relationships among tables, views, synonyms, and snapshots in a database. Advanced programmers can use associations to represent relationships within other datasources, such as spreadsheets, XML files, or flat text files.

When the datasource is a database, one-to-one and one-to-many associations usually map to foreign key relationships between tables in the database. Although you do not need to actually create a foreign key constraint between tables to create a one-to-one or one-to-many association between the corresponding entity objects, there should at least be an appropriate logical relationship between the tables.

Many-to-many associations are more complex than single foreign key relationships. A single many-to-many association corresponds to two foreign key relationships:

A one-to-many relationship between the source table and a third table, the intersection table
A one-to-many relationship between the destination table and the intersection table.

When the datasource is not a database, associations represent the relationships between objects in that datasource, as defined by the programmer.

For more information, see the related topics list.

Because associations are business domain components, you do not need to develop associations around your application's data needs. They should instead be the most logical representation of relationships within your data. If your datasource is well-designed, their structure can be isomorphic to that of the datasource.

JDeveloper will help you both engineer associations from existing foreign key constraints and generate foreign key constraints from associations.

Compositions

There are two kinds of one-to-many relationships:

Cases where the children are not, strictly speaking, part of the parent. For example, a single department is related to many employees, but employees are independently existing things, not just parts of departments. A company could eliminate a department without necessarily eliminating its members.
Cases where the children are part of the parent. For example, a line item is strictly part of a purchase order. It makes no sense to delete an order without deleting all of its line items.

You can represent this difference by making associations of the second type into compositions. Making a one-to-many association into a composition has four effects:

Oracle ADF Business Components prevents you from creating a child entity object instance with no parent
Oracle ADF Business Components prevents you from deleting a parent entity object instance without deleting all of its children (the composition can be configured to delete the children, or to throw an exception when this is attempted)
Oracle ADF Business Components attempts to acquire a lock on a parent row whenever it acquires a lock on one of its children
Oracle ADF Business Components marks a parent entity object instance as needing validation whenever it marks one of its children as needing validation

For more information, see the related topics list.