EclipseLink/UserGuide/JPA/Advanced JPA Development/Schema Generation/CascadeOnDelete

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Key API CascadeOnDelete

@CascadeOnDelete

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ON DELETE CASCADE is a database foreign key constraint option that automatically removes the dependent rows.

Use the @CascadeOnDelete annotation or the cascadeOnDelete property to specify that a delete operation performed on a database object is cascaded on secondary or related tables.

CascadeOnDelete

Performing a CascadeOnDelete on this object...	Does this...
Entity	Defines that secondary or joined inheritance tables should cascade the delete on the database
OneToOne mapping	The deletion of the related object is cascaded on the database. This is only allowed for mappedBy/target-foriegn key OneToOne mappings (because of constraint direction).
OneToMany mapping	The deletion of the related objects is cascaded on the database.
ManyToMany mapping	The deletion of the join table is cascaded on the database. (Target objects cannot be cascaded even if private because of constraint direction).
DirectCollection	The deletion of the direct table is cascaded on the database.
AggregateCollection	The deletion of the aggregate table is cascaded on the database.

@Target(value={METHOD,FIELD,TYPE})
@Retention(value=RUNTIME)
public @interface CascadeOnDelete

Cascading deletions behave as follows:

• Automatic DDL generation sets the onDeleteCascade flag on the ForeignKeyDefinition based on the mapping.

DeleteObject and DeleteAll queries check the descriptor and only delete from the first table if cascaded.

DirectCollection, AggregateCollection and ManyToMany do not execute the delete SQL, if cascaded.

OneToOne and OneToMany mappings record their dependencies as having been a delete on the database in the Unit of Work. Deletion then checks this to prevent executing the SQL. Note that DeleteObject queries still execute as normal, except that no SQL will be executed.

Configuration File

In the orm.xml descriptor file, specify cascade on delete as follows:

<source lang="xml">
<entity cascadeOnDelete="true">
<one-to-one cascadeOnDelete="true">
<one-to-many cascadeOnDelete="true">
<many-to-many cascadeOnDelete="true">
</source>

Version: 2.2.0 DRAFT
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Schema Generation	Schema Generation	@Index
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