Java @Entity persist with @OneToOne problem.1

@Entity
@NamedQuery(name = "Customer.getAll", query = "SELECT c FROM Customer c")
@SequenceGenerator(name = "SEQ_CUST", initialValue = 50)
public class Customer {

    // ======================================
    // =             Attributes             =
    // ======================================

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_CUST")
    @Cascade(CascadeType.ALL)
    @Column(name = "FK_CUSTOMER")
    private int id;
    @NotNull
    private String firstName;
    @NotNull
    private String lastName;
    @NotNull
    private String email;
    @NotNull
    private String phoneNumber;
    @NotNull
    private Date birth;

    public Customer(){
    }

    public Customer(String firstName, String lastName, String email, String phoneNumber, Date birth) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.email = email;
        this.phoneNumber = phoneNumber;
        this.birth = birth;
    }
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPhoneNumber() {
        return phoneNumber;
    }

    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }

    public Date getBirth() {
        return birth;
    }

    public void setBirth(Date birth) {
        this.birth = birth;
    }
    @Override
    public String toString() {
        return "Customer{" +
                "customerId=" + id +
                ", firstName='" + firstName + '\'' +
                ", lastName='" + lastName + '\'' +
                ", email='" + email + '\'' +
                ", phoneNumber='" + phoneNumber + '\'' +
                ", birth=" +  birth +
                '}';
    }

}