JPA - How to map relation with NON-KEY field.

Question

Hello.
Problem with mapping is NullPointerException when calling EntityManager em.createNativeQuery:
Table1 (Bm_Treeassoc):
MY_ID (Primary Key)
BOOKMARKID (-> MY_ID in Table2)
Text
Table2 (Bm_Bookmark):
MY_ID ( Primary Key)
Text
//CLASS BmTreeassoc
@OneToMany(targetEntity=BmBookmark.class, mappedBy="treeMaster", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
     private BmTreeassoc treeMaster = null ;
//CLASS BmBookmark
@ManyToOne(targetEntity=BmTreeassoc.class, fetch = FetchType.LAZY, cascade = CascadeType.ALL, optional = true)
     @JoinColumn(name="MY_ID", referencedColumnName="BOOKMARKID", unique=true)     
     private ArrayList<BmBookmark> bookmarks = new ArrayList<BmBookmark>() ;
This Leads to the exception.
Mapping form MY_ID to MY_ID instead BOOKMARKID will not throw the exception,
so I assume I have a problem with the KEY Field?
Any ideas?
Kind regards
Frank

Answer 1

OK,
after reflecting (after maniacally trying for days).
Here is the answer by myself:
I do not use the mapping stuff at all no more.
I solved my join by using a view:
CREATE VIEW SAPDEMO.VTree
     AS SELECT t.TreeID, b.MY_ID, b.CLIENTID, b.Nickname, u.URL
     FROM SAPDEMO.BM_TreeAssoc as t
          JOIN SAPDEMO.BM_BOOKMARK as B ON t.BookmarkID = b.MY_ID
          JOIN SAPDEMO.BM_URL as U ON b.URL = u.MY_ID
Create the entity and then do a:
select * from VTREE where clientid=1 and treeid=446
Works great, simple, fast.