UnitOrWork + DAO + EntityManager programatic transaction handling suggestion

UnitOfWork.java

// NOTE: This is not a by-the-book implementation of the UnitOfWork pattern. If you don't feel it is
// OK, then you can call this class Transaction or anything like that
public class UnitOfWork {
  
  // static reference to entityManagerFactory
  public static UnitOfWork createUnitOfWork() {
    EntityManager entityManager = entityManagerFactory.createEntityManager();
    return new UnitOfWork(entityManager);
  }
  
  private final EntityManager entityManager;
  private UnitOfWork(EntityManager entityManager) {
    this.entityManager = entityManager;
  }
  
  public void begin() {
    entityManager.getTransaction().begin();
  }
  
  public void rollback() {
    // for more robust support, this should be wrapped in a try/catch/finally block
    entityManager.getTransaction().rollback();
    entityManager.close();
  }
  
  public void commit() {
    // for more robust support, this should be wrapped in a try/catch/finally block
    entityManager.getTransaction().commit();
    entityManager.close();
  }
  
  public EntityManager entityManager() {
    return this.entityManager;
  }
  
}

UserBLImpl.java

public class UserBLImpl implements UserBL {

  // ...

  private void assignRightToUser(int userId, int rightId) throws SomeAppException{
    UnitOfWork unitOfWork = UnitOfWork.createUnitOfWork();
    UserDAO userDAO = new UserDAO(unitOfWork);
    RightDAO rightDAO = new RightDAO(unitOfWork);

    List<User> johns = userDAO.findUsersByName("John");
    try {
      unitOfWork.begin();
      
      // use userDAO and rightDAO at will...
      johns.get(0).setAge(123);
      userDAO.save(johns.get(0));
      
      unitOfWork.commit();
    } catch(SomeJpAException e) {
      unitOfWork.rollback();
      throw new SomeAppException(some message);
    }
  }
  
}

UserDAO.java

public class UserDAO {

  private final EntityManager entityManager;
  public UserDAO(UnitOfWork unitOfWork) {
    this.entityManager = unitOfWork.entityManager();
  }
  
  public User findUserById(int id) {
    return this.entityManager.find(User.class, id);
  }
  
  // other find methods... such as
  public List<User> findUsersByName(String name) {
    TypedQuery<User> query = this.entityManager.createQuery("SELECT u FROM User u WHERE BY u.name = :name", User.class);
    query.setParameter("name", name);
    return query.getResultList();
  }

  public void save(User user) {
    if (user.getId() == null) {
      this.entityManager.persist(user);     		
    }	else {
      this.entityManager.merge(user);    
    }
  }
  
}