One-to-one mapping


Use a One-to-One Mapping to define a relationship with one-to-many multiplicity.

  1. In the Persistence Outline view, select the field to map. The Persistence Properties view (for attributes) displays the properties for the selected.

  2. In the Map As field, select One-to-one.

  3. Use this table to complete the remaining fields on the Persistence Properties view.

    Property Description Default
    Target Entity The entity to which this attribute is mapped. null

    You do not need to explicitly specify the target entity, since it can be inferred from the type of object being referenced.

    Cascade Type See "Cascade Type" for details.
    • Default

    • All

    • Persist

    • Merge

    • Remove

    Default
    Fetch Type Defines how data is loaded from the database. See "Fetch Type" for details.
    • Eager

    • Lazy

    Eager
    Optional Specifies if this field is can be null. Yes
    Mapped By The database field that owns the relationship.
    Join Column Specify a mapped column for joining an entity association. See "Join Columns" for details.

Eclipse adds the following annotations to the field:

@OneToOne(targetEntity=<TARGET_ENTITY>, cascade=CascadeType.<CASCADE_TYPE>, 
    fetch = FetchType.<FETCH_TYPE>, mappedBy = "<MAPPED_BY>")
@JoinTable(joinColumns=@JoinColumn(name="<JOIN_COLUMN_NAME>"))


 

Related task

Mapping an entity

 

Related reference

Persistence Outline view
Persistence Properties view (for attributes)

 

Related concept

Understanding OR mappings
Understanding JSR220: EJB 3.0