// PARENT or ONE SIDE
@Entity
@Table(name = "User")
public class User {
   
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "userId")
    private Integer userId;
   
    @OneToMany(fetch=FetchType.EAGER)
    @Cascade({ org.hibernate.annotations.CascadeType.ALL, org.hibernate.annotations.CascadeType.DELETE_ORPHAN })
    @JoinTable(
            name="userSheets",
            joinColumns = @JoinColumn( name="sheetId"),
            inverseJoinColumns = @JoinColumn( name="userId")
    )
    private Set<Sheet> sheets;

}

// CHILDREN or MANY SIDE
@Entity
@Table(name = "Sheet")
public class Sheet {
    // Unidirectional so no mapping here per hibernate doc.
   // http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-mapping-association-collections

}

// SAVE CODE
public class UserDAO extends HibernateDaoSupport {
   @Transactional(readOnly=false)
   public void save(User newUser) {
      Session session = getHibernateTemplate().getSessionFactory().getCurrentSession();
      session.setFlushMode( FlushMode.COMMIT );

                // User table gets updated. Sheet table gets updated. userSheets does not. On read however, it is expected.
      getHibernateTemplate().saveOrUpdate(newUser);
   }
}

@Entity
@Table(name = "User")
public class User {   
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "userId")
    private Integer userId;

    @OneToMany(mappedBy="user")
    @Cascade({ org.hibernate.annotations.CascadeType.ALL, org.hibernate.annotations.CascadeType.DELETE_ORPHAN })
    private Set<Sheet> sheets;
}

@Entity
@Table(name = "Sheet")
public class Sheet {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "sheetId")
    private int sheetId;

    @ManyToOne
    @JoinColumn(name="userId")
    private User user;
}

DB UPDATE:
Removed JoinTable userSheets
Added userId to Sheets (created FK to user)

CODE UPDATE:
When instantiating a new sheet, need to make sure you call setUser() on Sheet to create the relationship.