Hibernate JPA @AssociationOverride Example

The @AssociationOverride annotation is used to override an association mapping (e.g. @ManyToOne, @OneToOne, @OneToMany, @ManyToMany) inherited from a mapped superclass or an embeddable.

JPA defines the @AttributeOverride annotation to handle this scenario. This way, the mapping conflict is resolved by setting up explicit name-based property-column type mappings.

If an Embeddable type is used multiple times in some entity, you need to use the @AttributeOverride and @AssociationOverride annotations to override the default column names defined by the Embeddable.

Considering you have the following Publisher embeddable type which defines a @ManyToOne association with the Country entity:

Embeddable type with a @ManyToOne association

@Embeddable
public static class Publisher {

private String name;

@ManyToOne(fetch = FetchType.LAZY)
private Country country;

//Getters and setters, equals and hashCode methods omitted for brevity

}

@Entity(name = "Country")
public static class Country {

@Id
@GeneratedValue
private Long id;

@NaturalId
private String name;

//Getters and setters are omitted for brevity
}
create table Country (
    id bigint not null,
    name varchar(255),
    primary key (id)
)

alter table Country
    add constraint UK_p1n05aafu73sbm3ggsxqeditd
    unique (name)

Overriding embeddable type attributes
@Entity(name = "Book")
@AttributeOverrides({
@AttributeOverride(
name = "ebookPublisher.name",
column = @Column(name = "ebook_publisher_name")
),
@AttributeOverride(
name = "paperBackPublisher.name",
column = @Column(name = "paper_back_publisher_name")
)
})
@AssociationOverrides({
@AssociationOverride(
name = "ebookPublisher.country",
joinColumns = @JoinColumn(name = "ebook_publisher_country_id")
),
@AssociationOverride(
name = "paperBackPublisher.country",
joinColumns = @JoinColumn(name = "paper_back_publisher_country_id")
)
})
public static class Book {

@Id
@GeneratedValue
private Long id;

private String title;

private String author;

private Publisher ebookPublisher;

private Publisher paperBackPublisher;

//Getters and setters are omitted for brevity
}
create table Book (
    id bigint not null,
    author varchar(255),
    ebook_publisher_name varchar(255),
    paper_back_publisher_name varchar(255),
    title varchar(255),
    ebook_publisher_country_id bigint,
    paper_back_publisher_country_id bigint,
    primary key (id)
)

alter table Book
    add constraint FKm39ibh5jstybnslaoojkbac2g
    foreign key (ebook_publisher_country_id)
    references Country

alter table Book
    add constraint FK7kqy9da323p7jw7wvqgs6aek7
    foreign key (paper_back_publisher_country_id)
    references Country