Using @JoinColumn VS not using @JoinColumn

[Duran Harris]

Hi all,

I would just like to clarify the difference between the following 2 code samples from EJB3 in Action:
First code sample:

 @Entity
@Table(name="ITEMS")
public class Item{
@Id
@Column(name="ITEM_ID")
protected Long itemId;
@OneToMany(mappedBy="item")
protected Set<Bid> bids;
}

@Entity
@Table(name="BIDS")
public class Bid{
@Id
@Column(name="BID_ID")
protected Long bidId;

@ManyToOne
@JoinColumn(name="BID_ITEM_ID",referencedColumnName="ITEM_ID")
protected Item item;
}   

2nd Code Sample:

 @Entity
@Table(name="ITEMS")
public class Item{
@Id
@Column(name="ITEM_ID")
protected Long itemId;
@OneToMany(mappedBy="item")
protected Set<Bid> bids;
}

@Entity
@Table(name="BIDS")
public class Bid{
@Id
@Column(name="BID_ID")
protected Long bidId;

@ManyToOne
protected Item item;
}   

The 2nd code sample is missing the @JoinColumn.

So in the 1st case it would be possible to use the foreign key in the User table to locate the relevant Bid/s using SQL.

Whereas the 2nd case wouldn't have a foreign key BUT it would still be possible to access the relevant Bid/s through the User object's reference to a collection of Bids albeit only via JPQL this time?