我想從數(shù)據(jù)庫中刪除商家表中的行和地址表中的行。商戶的表中有address_id。我已經(jīng)為 Merchant 和 Address 創(chuàng)建了 DAO。如何僅使用實體管理器來做到這一點？我省略了導(dǎo)入、getter 和 setter。似乎只刪除了Merchant表中的行，而保留了地址表中的行。任何幫助將不勝感激，謝謝。每當我刪除商家實體時，它都會保留地址id，并且不會刪除Address表中相應(yīng)的地址。我不明白為什么。@Entitypublic class Merchant {    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private int id;    private String name;    @OneToOne    private Address address;    public Merchant() {    }}public class MerchantDAO {    protected static EntityManagerFactory emf = Persistence.createEntityManagerFactory("hamzaspersistenceunit");    public void persist(Merchant merchant) {        EntityManager em = emf.createEntityManager();        em.getTransaction().begin();        em.persist(merchant);        em.getTransaction().commit();        em.close();    }    public void removeMerchant(Merchant merchant) {        EntityManager em = emf.createEntityManager();        em.getTransaction().begin();        em.remove(em.contains(merchant) ? merchant : em.merge(merchant));        em.getTransaction().commit();        em.close();    }}@Entitypublic class Address {    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private int id;    private String name;    private String streetAddress;    private String city;    private String state;    private String zipCode;    public Address(String name, String streetAddress, String city, String state, String zipCode) {        super();        this.name = name;        this.streetAddress = streetAddress;        this.city = city;        this.state = state;        this.zipCode = zipCode;    }}public class AddressDAO {    protected static EntityManagerFactory emf = Persistence.createEntityManagerFactory("hamzaspersistenceunit");    public AddressDAO() {    }    public void persist(Address address) {        EntityManager em = emf.createEntityManager();        em.getTransaction().begin();        em.persist(address);        em.getTransaction().commit();        em.close();    }