Configuring a Many-to-Many Mapping

Use a many-to-many mapping to represent the relationships between a collection of source objects and a collection of target objects. This mapping requires the creation of an intermediate table (the association table) for managing the associations between the source and target records.

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

For more information, see "Understanding Many-to-Many 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#manytomany.

Using Annotations

Example 7-23 shows how to use the @ManyToMany annotation to specify a many-to-many mapping for field projects and how to use the @JoinTable annotation to specify an association table.

Example 7-23 @ManyToMany

@ManyToMany(cascade=PERSIST)
@JoinTable(
    name="EJB_PROJ_EMP",
    joinColumns=@JoinColumn(name="EMP_ID", referencedColumnName="EMP_ID"),
    inverseJoinColumns=@JoinColumn(name="PROJ_ID", referencedColumnName="PROJ_ID")
)
public Collection getProjects() {
    return projects;
}