Module jakarta.persistence
Package jakarta.persistence

Annotation Type OneToOne

  • @Target({METHOD,FIELD})
@Retention(RUNTIME)
public @interface OneToOne
    Specifies a single-valued association to another entity class that has one-to-one multiplicity. It is not usually necessary to specify the associated target entity explicitly, since it can usually be inferred from the type of the object being referenced.

    If the relationship is bidirectional, the non-owning side must use the mappedBy() element of the OneToOne annotation to specify the relationship field or property of the owning side.

    A OneToOne association usually maps a unique foreign key relationship, either a foreign key column or columns with a unique constraint, or a relationship via a shared primary key. The JoinColumn annotation may be used to map the foreign key column or columns. Alternatively, an optional OneToOne association is sometimes mapped to a join table using the JoinTable annotation.

    The OneToOne annotation may be used within an embeddable class to specify a relationship from the embeddable class to an entity class. If the relationship is bidirectional and the entity containing the embeddable class is on the owning side of the relationship, the non-owning side must use the mappedBy() element of the OneToOne annotation to specify the relationship field or property of the embeddable class. The dot (.) notation syntax must be used in the mappedBy() element to indicate the relationship attribute within the embedded attribute. The value of each identifier used with the dot notation is the name of the respective embedded field or property.

    Example 1: One-to-one association that maps a foreign key column {@snippet : // On Customer class:

    Since:
    1.0

    • Optional Element Summary

      Optional Elements 
      Modifier and Type Optional Element Description
      CascadeType[] cascade
      (Optional) The operations that must be cascaded to the target of the association.
      FetchType fetch
      (Optional) Whether the association should be lazily loaded or must be eagerly fetched.
      java.lang.String mappedBy
      (Optional) The field that owns the relationship.
      boolean optional
      (Optional) Whether the association is optional.
      boolean orphanRemoval
      (Optional) Whether to apply the remove operation to entities that have been removed from the relationship and to cascade the remove operation to those entities.
      java.lang.Class<?> targetEntity
      (Optional) The entity class that is the target of the association.

    • Element Detail

      • targetEntity

        java.lang.Class<?> targetEntity
        (Optional) The entity class that is the target of the association.

        Defaults to the type of the field or property that stores the association.

        Default:
        void.class

      • cascade

        CascadeType[] cascade
        (Optional) The operations that must be cascaded to the target of the association.

        By default no operations are cascaded.

        Default:
        {}

      • fetch

        FetchType fetch
        (Optional) Whether the association should be lazily loaded or must be eagerly fetched.
        • The EAGER strategy is a requirement on the persistence provider runtime that the associated entity must be eagerly fetched.
        • The LAZY strategy is a hint to the persistence provider runtime.

        If not specified, defaults to EAGER.

        Default:
        jakarta.persistence.FetchType.EAGER

      • optional

        boolean optional
        (Optional) Whether the association is optional. If set to false then a non-null relationship must always exist.
        Default:
        true

      • mappedBy

        java.lang.String mappedBy
        (Optional) The field that owns the relationship. This element is only specified on the inverse (non-owning) side of the association.
        Default:
        ""

      • orphanRemoval

        boolean orphanRemoval
        (Optional) Whether to apply the remove operation to entities that have been removed from the relationship and to cascade the remove operation to those entities.
        Since:
        2.0
        Default:
        false