JPA bidirectional relation, JoinColumn not populated

Question

I am trying to build a bidirectional relation. When I am trying to save an entry, the item_id will be null in the Details table, everything else is populated.

inverse side, Item class:

@OneToMany(targetEntity = Details.class, mappedBy = "item", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private Set<Details> details;

owning side, Details class:

@ManyToOne(targetEntity=Item.class, fetch = FetchType.LAZY)
@JoinColumn(name="item_id")
private Item item;

What do i miss?

Thanks