Configuring a Many-to-One Mapping

Use a many-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 a many-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#manytoone.

Using Annotations

Example 7-21 shows how to use the @ManyToOne annotation to specify a many-to-one mapping for field manager.

Example 7-21 @ManyToOne

@ManyToOne(cascade=PERSIST, fetch=LAZY)
@JoinColumn(name="MANAGER_ID", referencedColumnName="EMP_ID")
public Employee getManager() {
    return manager;
}