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

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Elug api package icon.png 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 <cascade-on-delete> XML element 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 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.

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

Usage of @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.

Configuration File

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

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

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Example

@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;
    ...
}
See also, DeleteCascade Example