Many to One JPA (wrapping given tables)
===

I have a **m:n** relationship **book - borrow - user**, the borrow is the join table.

The tables are given (can not be changed):

-    on one side they are used by jdbc app as well.
-    on the other side i would like to use them via jpa


book(book_id) - borrow(book_id,used_id) - user(user_id)
 
     used jpa annotations:
     User:
     @OneToMany(targetEntity=BorrowEntity.class, mappedBy="user")
     @JoinColumn(name="USER_ID", referencedColumnName="USER_ID")	
     private List<BorrowEntity>borrowings;

     Book: 
     @OneToMany(targetEntity=BorrowEntity.class, mappedBy="book")
     @JoinColumn(name="BOOK_ID", referencedColumnName="BOOK_ID")
     private List<BorrowEntity>borrowings;

*My problem is that by the settings above it adds some extra (undesired) fields to the borrow table:*

'user_USER_ID' and 'book_BOOK_ID' 

**How can I configure the jpa annotations to keep just Borrow:user_id,book_id which is enough the many to one ?**


Take a look at the picture which tells more:

![book borrowing][1]


  [1]: http://i.stack.imgur.com/0n2kQ.png
