在数据库中添加NULL

Question

@Entity
@Table(name = "UserDetails")
public class UserDetails {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "userId")
    private int userId;

    @Column(name = "UserName")
    private String userName;

    @OneToMany
    @JoinColumn(name = "address")
    private Collection<Address> address = new ArrayList<Address>();
}

@Entity
@Table(name = "address")
public class Address {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private int id;
    @Column(name = "city")
    private String city;
}

UserDetails ud=new UserDetails();
ud.setUserName("User 1");

Address ad1=new Address();
ad1.setCity("Mumbai");

Address ad2=new Address();
ad1.setCity("Pune");

ud.getAddress().add(ad1);
ud.getAddress().add(ad2);

Session session=factory.openSession();
session.beginTransaction();
session.save(ud);
session.save(ad1);
session.save(ad2);


session.getTransaction().commit();
session.close();

userId       UserName     Address
1            User 1       NULL

Id      City    Address
1       Pune    1
2       NULL    1

Answer 1

Address ad2=new Address();
ad1.setCity("Pune");

您正在将城市pune设置为address1，而不是address2尝试将其更改为

 Address ad2=new Address();
    ad2.setCity("Pune");

更新

您的用户表adrees列为null，因为您的pojo中没有映射字段for address，无论如何，您的数据库模式设计方法是错误的，实现了onetomany关系。请在这里查看一对多冬眠的正确方式