Configuring an One-to-One Mapping

Use an one-to-one mapping to represent simple pointer references between two Java objects. In Java, a single pointer stored in an attribute represents the mapping between the source and target objects. Relational database tables implement these mappings using foreign keys.

You define an one-to-one mapping at one of the property (getter or setter method) or field level of your entity.

For more information, see "Understanding One-to-One Mapping" in the Oracle TopLink Developer's Guide.

Note:

For an EJB 3.0 basic mapping code example, see: http://www.oracle.com/technology/tech/java/oc4j/ejb3/howtos-ejb3/howtoejb30mappingannotations/doc/how-to-ejb30-mapping-annotations.html#onetoone.

Using Annotations

Example 7-20 shows how to use the @OneToOne annotation to specify an one-to-one mapping for field address.

Example 7-20 @OneToOne

@OneToOne(cascade=ALL, fetch=LAZY)
@JoinColumn(name="ADDR_ID")
public Address getAddress() {
    return address;
}