@CascadeOnDelete

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

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

Annotation Elements

There are no elements for this annotation.

Usage

You can place @CascadeOnDelete on any relationship in which the target is defined as foreign key to the source Entity.

Add the annotation on the source relationship: @OneToOne, @OneToMany, @ManyToMany, and @ElementCollection You can also add @CascadeOnDelete to an Entity with a @SecondaryTable or JOINED inheritance. Table 2-8 describes the affect of placing @CascadeDelete on these different elements

Table 2-8 Using @Cascade on Different Elements

Element	Effect of @CascadeOnDelete
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-foreign key OneToOne mappings (because of constraint direction).
OneToMany mapping	For a OneToMany using a `mappedBy` or `JoinColumn`, the deletion of the related objects is cascaded on the database. For a OneToMany using a `JoinTable`, the deletion of the join table is cascaded on the database (target objects cannot be cascaded even if private because of constraint direction).
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).
ElementCollection mapping	The deletion of the collection table is cascaded on the database.

@CascadeOnDelete has the following behavior:

DDL generation: If DDL generation is used, the generated constraint will include the cascade deletion option.
Entity: Remove will not execute SQL for deletion from secondary or joined inheritance tables (as constraint will handle deletion).
OneToOne: If the mapping uses cascading or orphanRemoval, SQL will not be executed to delete target object.
OneToMany: If the mapping uses cascading or orphanRemoval, SQL will not be executed to delete target objects.
ManyToMany: SQL will not be executed to delete from the join table.
ElementCollection: SQL will not be executed to delete from the collection table.
Cache: Cascaded objects will still be removed from the cache and persistence context.
Version locking: Version will not be verified on deletion of cascaded object.
Events: Deletion events may not be executed on the cascaded objects if the objects are not loaded.
Cascading: The remove operation should still be configured to cascade in the mapping if using CascadeOnDelete.

Examples

Example 2-18 shows the cascading deletion of the Employee secondary table and all of its owned relationships.

Example 2-18 Using @CascadeOnDelete Annotation

@Entity
@SecondaryTable(name="EMP_SALARY")
@CascadeOnDelete
public class Employee{
    @Id
    private long id;
    private String firstName;
    private String lastName;
    @Column(table="EMP_SALARY")
    private String salary;
    @OneToOne(mappedBy="owner", orphanRemoval=true, cascade={CascadeType.ALL})
    @CascadeOnDelete
    private Address address;
    @OneToMany(mappedBy="owner", orphanRemoval=true, cascade={CascadeType.ALL})
    @CascadeOnDelete
    private List<Phone> phones;
    @ManyToMany
    @JoinTable(name="EMP_PROJ")
    @CascadeOnDelete
    private List<Project> projects;
    ...
}

In the eclipselink-orm.xml descriptor file, specify cascade on delete as shown in Example 2-19

Example 2-19 Using <cascade-on-delete> XML

...
<cascade-on-delete>true</cascade-on-delete>
...