CODEWITHSUNDEEP
javajakarta-eejpaannotations
Honza Zidek
Honza Zidek

Reputation: 19926

Is the JPA @Embedded annotation mandatory?

I have tried omitting the @Embedded annotation and still the fields have been embedded in the table. I cannot find anything which would say that the @Embedded annotation is optional.

Is it or is it not optional?

The following code

@Embeddable
public class Address {
    String city;
    String street;
}

@Entity
public class Person {
    String name;
    @Embedded // it seems that it works even if this annotation is missing!?
    Address address;
}

generates always the same table

person
    name
    city
    street

even if I do not specify @Embedded.

My configuration:

The JPA specification says:

http://docs.oracle.com/javaee/7/api/javax/persistence/Embedded.html

@javax.persistence.Embedded

Specifies a persistent field or property of an entity whose value is an instance of an embeddable class. The embeddable class must be annotated as Embeddable.

http://docs.oracle.com/javaee/7/api/javax/persistence/Embeddable.html

@javax.persistence.Embeddable

Specifies a class whose instances are stored as an intrinsic part of an owning entity and share the identity of the entity. Each of the persistent properties or fields of the embedded object is mapped to the database table for the entity.

Upvotes: 15

Views: 4226

Answers (2)

Kevin Peters
Kevin Peters

Reputation: 3444

In case of using Hibernate it does not matter if you annotate the field itself (as @Embedded) or if you annotate the referenced class (as @Embeddable). At least one of both is needed to let Hibernate determine the type.

And there is a (implicit) statement about this inside the Hibernate documentation, take a look here: http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/mapping.html#mapping-declaration-component

It says:

The Person entity has two component properties, homeAddress and bornIn. homeAddress property has not been annotated, but Hibernate will guess that it is a persistent component by looking for the @Embeddable annotation in the Address class.

Upvotes: 4

asm0dey
asm0dey

Reputation: 2931

Embedded-Embeddable is not mandatory, but it gives you nice OOP perspective of your entities' relationship. Another way to do such a thing - is to use OneToOne mapping. But in such a case entity WILL be written to separate table (while in case of embedded it CAN be written to the separate table in your DB).

Upvotes: -3

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