Thank you for helping me! I found the error I did. In my code where I assigned all objects I missed to add the B item to the list of B:s in A. Doing this resolved my problem. The following steps must be applied: 1. Create A 2. Create all B:s and add them to A 3. Create C by using A and the expected B I missed to add the B, that was mapped from A and C, to A. Kind of stupidness from my side. I put my working code here for all of you who are interested in this: | @Entity | @Table(name = "A") | public class A implements Serializable { | | @Id | @GeneratedValue(strategy = GenerationType.IDENTITY) | @Column(name = "Aid") | private Integer id; | | @OneToOne(cascade = CascadeType.ALL, mappedBy = "a", fetch = FetchType.EAGER) | private C c; | | @OneToMany(cascade = CascadeType.ALL, mappedBy = "a", fetch = FetchType.EAGER) | private List<B> bs = new ArrayList<B>(); | | ... | | protected A() {}; | | public A(...) { | ... | } | | public List<B> getBs() { | return bs; | } | | public void setBs(List<B> bs) { | this.bs = bs; | } | | public void addB(B b) { | | b.setA(this); | this.bs.add(b); | } | | public C getC() { | return c; | } | | public void setC(C c) { | c.setA(this); | this.c = c; | } | | ... | } | | | | @Entity | @Table(name = "B") | public class B implements Serializable { | | @Id | @GeneratedValue(strategy = GenerationType.IDENTITY) | @Column(name = "Bid") | private Integer id; | | @ManyToOne | @JoinColumn(name = "Aid", nullable = false) | private A a; | | ... | | protected B() {}; | | public B(A a, ...) { | | this.a = a; | ... | } | | public Integer getId() { | return id; | } | | public void setId(Integer id) { | this.id = id; | } | | public A getA() { | return a; | } | | public void setA(A a) { | this.a = a; | } | | ... | } | | | | @Entity | @Table(name = "C") | public class C implements Serializable { | | @Id | @GeneratedValue(strategy = GenerationType.IDENTITY) | @Column(name = "Cid") | private Integer id; | | @OneToOne | @JoinColumn(name = "Aid", nullable = false) | private A a; | | @OneToOne | @JoinColumn(name = "Bid", nullable = false) | private B b; | | | protected C() {}; | | public C(A a, | B b) { | | this.a = a; | this.b = b; | } | | public Integer getId() { | return id; | } | | public void setId(Integer id) { | this.id = id; | } | | public A getA() { | return a; | } | | public void setA(A a) { | this.a = a; | } | | public B getB() { | return b; | } | | public void setB(B b) { | this.b = b; | } | } | | Finally some points: - There is an error in my first post. "... mappedBy="A"..." shall be "... mappedBy="a"...". My mistake in the post. - This fix requires the C table to carry its own primary key, a Cid. - As you say Felix, it doesn't look good to point out Aid twice. This shall work, but it seems to be a bug in hibernate (see http://forum.hibernate.org/viewtopic.php?t=970823). JBoss 4.0.5.GA is using Hibernate 3.2, it shall be fixed in Hibernate 3.3.0. I haven't tried the join table, I will check it out and se what more it gives to me. It might be a kind of shortcut for my C table mapping. Thanks again for quick response. Best Oskar View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4033902#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...