Duplicate creation of JPA entity

Question

I'm quite confused, I'm trying to find out why I'm getting the creation of two Customers in the database with the following code with no luck. I tried to cut all the noise from the code, I hope I didn't erased anything important for the resolution of the problem. Here are in the following order : Entities, DAOs, Services and the SpecialService with the specialTreatment which holds the bogus behavior.

In the specialTreatment the aim is to get an existing Order with no Customer linked to it, create a new Customer, and associate it to the order.

Entities :

Order.java :

@Entity
public class Order {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "pk_id_order")
    private Integer id;

    // Other fields ...

    @BatchFetch(value = BatchFetchType.IN)
    @JoinColumn(name = "fk_id_customer", referencedColumnName = "pk_id_customer")
    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    private Customer customer;

    // Other fields ...

    // Getter & setters for each field

    @Override
    public int hashCode() {
        int hash = 7;
        hash = 79 * hash + (this.id != null ? this.id.hashCode() : 0);

        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null || !(obj instanceof Order)) {
            return false;
        }

        final Order other = (Order) obj;
        if (this.id != other.id && (this.id == null || !this.id.equals(other.id))) {
            return false;
        }

        return true;
    }
}

Customer.java :

@Entity
public class Customer {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "pk_id_customer")
    private Integer id;

    // Other fields

    @OrderBy(value = "createdAt DESC")
    @OneToMany(mappedBy = "customer", fetch = FetchType.LAZY)
    private List<Order> orders;

    @Override
    public int hashCode() {
        return (id != null ? id.hashCode() : 0);
    }

    @Override
    public boolean equals(Object object) {
        if (object == null || !(object instanceof Customer)) {
            return false;
        }

        final Customer other = (Customer) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }

        return true;
    }
}

DAOs :

@Repository
@Transactional
public class CustomerDao {

    @PersistenceContext
    protected EntityManager em;

    public void create(Customer customer) {
        this.em.persist(customer);
    }
}

@Repository
@Transactional
public class OrderDao {

    @PersistenceContext
    protected EntityManager em;

    public Order edit(Order order) {
        return this.em.merge(order);
    }
}

Services :

@Service
@Transactional
public class CustomerService {

    @Autowired
    private CustomerDao customerDao;

    public void create(Customer customer) {
        this.customerDao.create(customer);
    }
}

@Service
@Transactional
public class OrderService {

    @Autowired
    private OrderDao orderDao;

    public void edit(Order order) {
        this.orderDao.edit(order);
    }
}

@Service
@Transactional
public class SpecialService {

    @Autowired
    private CustomerService customerService;

    @Autowired
    private OrderService orderService;

    @Transactional(propagation = Propagation.REQUIRES_NEW)
    public void specialTreatment(Order order) {
        Customer customer = new Customer();
        // Fill customer ...

        this.customerService.create(customer); // LINE X

        order.setCustomer(customer); // LINE Y

        this.orderService.edit(order);
    }
}

Note : When commenting line X : - There is no customer created (as expected), the order is edited as expected When commenting line Y : - The customer is created as expected (only one row) but it is not linked to my Order

The code is called from a Spring MVC controller

Any advice ?