jpa - Hibernate Best Practices: Avoiding Many-To-Many and 'exotic' relationships

Question

The hibernate best practices states that many-to-many associations are rare and should be avoided.

Do not use exotic association mappings:

Practical test cases for real many-to-many associations are rare. Most of the time you need additional information stored in the "link table". In this case, it is much better to use two one-to-many associations to an intermediate link class. In fact, most associations are one-to-many and many-to-one. For this reason, you should proceed cautiously when using any other association style.

A basic and common case would be: user can be in more than one team and a team can have more than one member.

Is there an alternative to using @ManyToMany, other than creating an entity for the join table? In the case of team/member, there is no additional data in the join table, so having Team>TeamMembership>User is not so practical.

Answer 1

There is nothing intrinsically wrong with using @ManyToMany but in practice, you rarely have the opportunity to use it. Usually you need additional attributes on the link itself, at which point, the relationship becomes an entity of its own.

One example from my experience was the kind of person/team relationship you described. I used a @ManyToMany at first, but had to turn it into a @OneToMany once I needed to add an effective-date on the relationship (person belongs to team at specific point in time).