One-To-many & Many-To-One - @Join columns on both sides or mapped-by:

[CatchSandeepVaid]

[P-279 of EJB3 In Action] states:
"Note that the exact @JoinColumn vspecification could have been repeated for both the Bid.item and Item.bids persistent fields on
either side of the relationship."

[P-280 of EJB3 In Action] states:
"The persistence provider will generate deployment-time errors if you specify @JoinColumn on both sides of a bidirectional one-tomany
relationship."

Aren;t these 2 statements contradictory?

[r035198x]

In what way?

[CatchSandeepVaid]

Stmt1: It says you can specify this annotation on both sides
Stmt2: It will give you deployment time errors.

[r035198x]

Does the book say that for the same type of relationship?
i.e is the first part referring to bi-directional one-to-many relationship as well?