# One-to-one mapping

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

1. In the JPA Structure view, select the field to map.

2. Right-click the field and then select Map As > One-to-One. The JPA Details view (for attributes) displays the properties for the selected.

   JPA Details, One-to-one Mapping

3. Complete each field in the One-to-One Mapping area.

4. Complete the remaining areas in the JPA Details view (for attributes):

   - Joining Strategy

   - Derived Identity

Eclipse adds the following annotations to the field:

    @OneToOne(targetEntity=<TARGET_ENTITY>, =Type.<_TYPE>,
        fetch = FetchType.<FETCH_TYPE>, mappedBy = "<MAPPED_BY>")
    @JoinColumn(name="<JOIN_COLUMN_NAME>", referencedColumnName=
        "<JOIN_COLUMN_REFERENCED_COLUMN>", insertable = <INSERTABLE>,
        updatable = <UPDATABLE>)

Related tasks

- Mapping an entity

Related references

- JPA Structure view

- JPA Details view (for attributes)

- Joining Strategy

- Derived Identity

Related concepts

- Understanding OR mappings

- Understanding Java Persistence API