空的外键，在ManyToOne关系中使用hibernate [4.1.1]注释 [英] Null foreign key, in ManyToOne relation using hibernate [4.1.1] annotations

问题描述

我试图用 Hibernate 4.1.1 持久化一对多和多对一的关系，但是外键始终是 NULL 。 / p>

有两个实体： Account 和 Client 。一个客户可以有多个帐户 。

下面是这些类（只有重要的）：
$ b

Account.java

  @Entity 
 @Table（name =account）
 public class Account实现Serializable {
 private Client client; 
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 @Column（name =id）
 public long getId（）{
返回ID; 
 
 $ b @ManyToOne 
 @JoinColumn（name =id_client）
 public Client getClient（）{
 return client; 
 
 
 code 
 $ b $ p $ Client.java   / b> 
 
 
  @Entity 
 @Table（name =client）
 public class Client implements Serializable {
私人列表<帐户>账户; 
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 @Column（name =id）
 public long getId（）{
返回ID; 
 
 
 @OneToMany（mappedBy =client，cascade = CascadeType.ALL，fetch = FetchType.EAGER）
 public List< Account> getAccounts（）{
返回帐户; 
 
 
 
 
 $ p   / p> 
 
 
  session.beginTransaction（）; 
 
客户端客户端=新客户端（）; 
帐户帐户1 =新帐户（）; 
帐户account2 =新帐户（）; 
 
 a.addAccount（account1）; 
 a.addAccount（account2）; 
 
 session.save（client）; 
 session.getTransaction（）。commit（）; 
  
运行时，Hibernate将外键添加到表中：
 
 
 
  Hibernate：alter table account add index FKB9D38A2D3B988D48（id_client），add constraint FKB9D38A2D3B988D48 foreign key（id_client）references client（id） 
 
 
 
两个帐户都有id_client列 NULL 。
 
 
 
我试着把 nullable = false 在@JoinColumn关系，但只是调用一个异常。
 
 
 
 线程main中的异常org.hibernate.exception.ConstraintViolationException： id_client'不能为空 
解决方案
我忘了将客户端添加到帐户中。
  account1.setClient（client）; 
 account2.setClient（client）; 
  
现在可以运作了。感谢您的小费。 ;） 
I am trying to persist a one-to-many and a many-to-one relation using Hibernate 4.1.1 but the foreign key is always NULL.

There are two entities: Account and Client. A Client could have multiple Accounts while an Account has exactly one Client.

Here are the classes (only what matters):

Account.java
@Entity
@Table(name = "account")
public class Account implements Serializable {
    private Client client;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    public long getId() {
        return id;
    }

    @ManyToOne
    @JoinColumn(name = "id_client")
    public Client getClient() {
        return client;
    }
}
Client.java
@Entity
@Table(name = "client")
public class Client implements Serializable {
    private List<Account> accounts;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    public long getId() {
        return id;
    }

    @OneToMany(mappedBy = "client", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    public List<Account> getAccounts() {
        return accounts;
    }
}
Test.java
session.beginTransaction();

Client client = new Client();
Account account1 = new Account();
Account account2 = new Account();

a.addAccount(account1);
a.addAccount(account2);

session.save(client);
session.getTransaction().commit();
While running, Hibernate adds the foreign key to the table:

Hibernate: alter table account add index FKB9D38A2D3B988D48 (id_client), add constraint FKB9D38A2D3B988D48 foreign key (id_client) references client (id)

Both accounts have id_client column NULL.

I tried putting nullable = false at the @JoinColumn relation but that just invoked an exception.

Exception in thread "main" org.hibernate.exception.ConstraintViolationException: Column 'id_client' cannot be null
解决方案
Figured it out. I forgot to add the client to the accounts.
account1.setClient(client);
account2.setClient(client);
Now it works. Thank you for the tips. ;)

                        
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