Hi,

I have some classes/code like this:
public class Item {
private Long id;
private List<Bid> bids;
@Id
@GeneratedValue
public Long getId() {
return id;
}

@OneToMany(cascade= CascadeType.ALL, mappedBy="item")
public List<Bid> getBids() {
return bids;
}
// getter/setters ...
}

public class Bid {
private Long id;
private Item item;

@Id
@GeneratedValue
public Long getId() {
return id;
}

@ManyToOne()
@JoinColumn(name = "item_id")
public Item getItem() {
return item;
}

// getters/setters ...
}

I did not new the instance bids, but why I still can access the elements with following code?

Item item = (Item) _session.load(Item.class, new Long(3));
System.out.println(item.getBids().get(0).getId());
which is correct?
private List<Bid> bids;
or
private List<Bid> bids = new ArrayList<Bid>();

Help me understand this, thanks.

A.C.

When you load/get object via Hibernate, it automatically instantiates collections (more precisely: collection references in loaded object are set to Hibernate's own implementations).

If you did this:


this would raise NullPointerException, because, as you said, bids are not instantiated. So, generally, it is wise to instantiate collections, because you probably want to use them, even if they are not managed by Hibernate yet.

Greetings