Extra fields on Many To Many mapping tables

[jjklappenbach]

Our company is developing an EJB solution for a schema that features auditing fields on every table, including the many-to-many mapping tables. The audit fields are constrained to non-null values, and must include dates as well as the committing user.

The problem that I've encountered is that these fields are not handled with the @ManyToMany annotation model, at least with the current argument set we're using for the annotation. Is there additional annotation or perhaps configuration descriptors that can be used to have EJB3 / Hibernate automatically handle those fields? I've seen examples of Interceptors being used, but discussion of that strategy often leads to business owners looking like they've just stepped on a grave.

Having additional, non-null fields on mapping tables can't be a particularly rare case. How can this best be handled through EJB3?

One other solution I've found is limiting cascades to REFRESH and DELETE for the @ManyToMany, and creating explicit service layer API methods for association. That means creating an @Entity for each mapping table -- basically extra work.

Thanks for your time in advance,

Julian Klappenbach
Lead Software Developer
Ramp Technology Group

[mazz]

There are threads on this in here already on this. ManyToMany doesn't handle those extra columns. I've come to terms with this by simply ignoring ManyToMany and always implementing my M-2-M relationships using OneToMany/ManyToOne - even if I don't currently use other columns in my association tables - because invariably, I always wind up needing to add columns in the end anyway. And I don't want to waste the time converting the ManyToMany to the OneToMany/ManyToOne. Just do it in the beginning and that leaves you free to add columns in the future.