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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 <cascade-on-delete> XML element to specify that a delete operation performed on a database object is cascaded on secondary or related tables.

@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.

@CascadeOnDelete 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;
    ...
}

Specifying Cascade on Delete in orm.xml

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

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

See also, DeleteCascade Example

@Index	Schema Generation	Appending Strings to CREATE_TABLE Statements
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