為什么不能使用JPA TopLink注釋加入第3個表？

Question

我有簡單的3張桌子：

Users
-id
-name

Addresses
-id
-user_id  //FK
-location

Phone
-id
-number
-address_id //FK

• 用戶可以有多個地址
• 地址可以有很多電話

因此，應用於每個實體類的注釋將類似於：

用戶數

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
    private List<Addresses> addresses;

地址

    @ManyToOne()
    @JoinColumn(name = "user_id")
    private Users user;

    @OneToMany(mappedBy = "address")
    private List<Phone> phone;

電話

    @ManyToOne()
    @JoinColumn(name = "address_id")
    private Addresses address;

上面的注釋應創建關系：

users  (1) ----- (n) addresses (1) ------ (n) phone

然后，我在MySQL中創建了一些測試數據，並嘗試運行測試以查看返回“用戶”的查詢結果是否包括對地址和電話的引用。

我已經嘗試使用僅使用用戶和地址的2表，並得到了確定的結果。

現在，我添加了“電話”表，它是第3個表，然后出現以下錯誤。 這是聯接3個或更多表的正確方法嗎？

測試碼

      try {
          //get entity manager
          String WEB_PU = "NoJSFPU";
          EntityManagerFactory factory =                 Persistence.createEntityManagerFactory(WEB_PU);
          EntityManager em = factory.createEntityManager();

          //run query
          List<Users> usersList = em.createQuery("SELECT u FROM Users u").getResultList();

           //loop to print out each result
           for(Users item : usersList) {
               //display user info
               System.out.println(item.getId() + " " + item.getFirstname());

               List<Addresses> addrs = item.getAddresses();
               for(Addresses ad : addrs) {
                  //display address info
                  System.out.println("Address:::" + ad.getLocation());

                  List<Phone> pho = ad.getPhone();
                  for(Phone p : pho) {
                     //display phone info
                     System.out.println("phone#" + p.getNumber());
                  }

                }//end inner for
            }//end outer for
                System.out.println("==========================");

            }
            catch(Exception e) {
                System.out.println("seriously wtf: " + e.toString());
                System.exit(1);
            }

錯誤

Exception Description: predeploy for PersistenceUnit [NoJSFPU] failed.
Internal Exception: Exception [TOPLINK-7250] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException
Exception Description: [class local.test.session.Addresses] uses a non-entity [class local.test.session.Phone] as target entity in the relationship attribute [private java.util.List local.test.session.Addresses.phone].

Answer 1

我想通了。 必須使用@JoinTable批注指定。

現在，如果我運行測試代碼，則可以從所有3個表中獲取數據：D

地址

@ManyToOne
@JoinTable(name = "Addresses", joinColumns = {@JoinColumn(name="user_id", 
referencedColumnName = "user_id") } )
private Users user;

電話

@ManyToOne
@JoinTable(name = "Phone", joinColumns = {@JoinColumn(name="address_id", 
referencedColumnName = "address_id") } )
private Addresses address;