Creating EJB 3.0 Entity Relationships - EJB 3.0 Database Persistence with Oracle Fusion Middleware 11g - page 217

The Edition entity class
The Edition entity bean has the properties id and edition :
private int id;
private String edition;
The Edition entity defines a NamedQueries findEditionAll() (which finds all the
Edition instances) and findEditionByEdition() (which finds an Edition by the
edition date):
@NamedQueries( { @NamedQuery(name = "findEditionAll",
query = "SELECT e FROM Edition e"),
@NamedQuery(name = "findEditionByEdition",
query = "SELECT e from Edition e
WHERE e.edition = :edition")
} )
The Edition entity is on the non-owning side of a bidirectional many-to-many
relationship with the Catalog entity. Therefore, we specify the @ManyToMany
annotation with the mappedBy element. We don't need to specify a join table, as
Edition entity is the non-owning side. The cascade element is set to cascade MERGE ,
PERSIST , and REFRESH operations:
@ManyToMany(cascade =
{ CascadeType.MERGE, CascadeType.PERSIST,
CascadeType.REFRESH },
mappedBy = "editions")
protected List<Catalog> getCatalogs() {
return catalogs;
}
The editions field is defied in the Catalog entity, which is the owning side of
the relationship. The Edition entity also has a one-to-many relationship with the
SECTION entity. In a one-to-many relationship the many side is made the owning
side; therefore, the many side has the join table. But, a join table may be added on
the one side also to initiate cascade operations from the one side. Therefore, we have
added a join table on the one side ( Edition entity) also:
@OneToMany(cascade = CascadeType.ALL, mappedBy = "edition")
@JoinTable(name = "EditionSection",
joinColumns = { @JoinColumn(
name = "editionId", referencedColumnName = "ID") },
inverseJoinColumns = { @JoinColumn(
name = "sectionId", referencedColumnName ="ID") } )