Working on some legacy hibernate code.

How do I do the following with hbm.xml(hibernate mapping file) instead of with annotations?

@Table(name="users", uniqueConstraints = {
    @UniqueConstraint(columnNames={"username", "client"}),
    @UniqueConstraint(columnNames={"email", "client"})
})
public class User implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    private int id;
    private String username;
    private String email;
    private Client client;
}