How to create foreign key in Hibernate on Integer column

I have an entity in Java and I would like Hibernate to create a foreign key from an Integer field (since I don't have an object reference):

@Entity
public class Invoice {

    ...
    @Column(nullable = true)
    private Integer generatedBy;
    ...

I think I'd like to do something like this with an attribute:

    @ForeignKey(name="FK_Invoice_开发者_开发知识库GeneratedBy", references="UserTable.UserId")
    @Column(nullable = true)
    private Integer generatedBy;

What is the best way to achieve this? I would preferably not have to maintain these relationships in a separate file (if possible).

There doesn't seem to be a solution to this, thus accepting this as an answer.

There is a way to do it, but it is not very nice...

You can have your integer attribute, AND an object attribute mapped this way:

@Column(ame = "GENERATED_BY", nullable = true)
private Integer generatedBy;

@ForeignKey(name="FK_Invoice_GeneratedBy")
@JoinColumn(name = "GENERATED_BY", nullable = false, updatable = false, insertable = false)
private User generatedByUser;

You may keep no external access to your generatedByUser field, it will only show hibernate that there is a relationship. You can set the Integer field at will, when you load this object from DB later you'll have your user reference.

Again, not very pretty, but can be useful sometimes.