@OneToMany 关系不会在子表中保存父级的主键

Question

假设存在三个 JPA 实体。APerson和2是一对多的关系。当我尝试保存 Person 时AD_P_ID，AC_P_ID外键始终为空。这些字段的预期值是人员 ID。我究竟做错了什么？

1. AccountPerson.java：这包含与Entity 类的一对多关系Address：

   @Entity
   @Table(name = "A2C_PERSON")
   class Person implements Serializable {
   
       private long id;
   
       private List<Account> acs;
   
       private List<Address> ads;
   
       @OneToMany(cascade=CascadeType.ALL, mappedBy = "person")
       public List<Account> getAccount() {
           return this.acs;
       }
   
       @OneToMany(cascade=CascadeType.ALL, mappedBy = "person")
       public List<Address> getAddress() {
           return this.ads;
       }
   }
   

2. 账户.java

   @Entity
   @Table(name = "A2C_ACCOUNT")
   public class Account implements Serializable {
   
       private long id;
   
       private Person person;
   
       @ManyToOne(cascade=CascadeType.ALL, fetch = FetchType.LAZY)
       @JoinColumn(name = "AC_P_ID")
       public Person getPerson() {
           return this.person;
       }
   }
   

3. 地址.java

   @Entity
   @Table(name = "A2C_ADDRESS")
   public class Address implements Serializable {
   
       private long id;
   
       private Person person;
   
       @ManyToOne(cascade=CascadeType.ALL,fetch = FetchType.LAZY)
       @JoinColumn(name = "AD_P_ID")
       public Person getPerson() {
           return this.person;
       }
   }
   

救人的代码：

Person p = new Person();

Account ac1 = new Account();
Account ac2 = new Account();
List<Account> acList = new ArrayList<>();
acList.add(ac1);
acList.add(ac2)

Address ad1 = new Adddress();
Address ad2 = new Adddress();
List<Address> adList = new ArrayList<>();
acList.add(ad1);
acList.add(ad2)

p.setAcs(acList);
p.setAds(adList);

personRepo.save(p);

Answer 1

@JoinColumn表示关系的所有者。

“MappedBy”表示反面。

所以：

@OneToMany(mappedBy = "parent")
private Collection<Child> childCollection;

不会将父级引用设置为其子级。这是你的情况。您可以像 Maciej 建议的那样手动设置它，但它会添加一些锅炉代码。

要自动设置父级对其子级的引用，您必须按以下方式定义关系的所有者。

@OneToMany(cascade = CascadeType.ALL)
@JoinColumn
private Collection<Child> childCollection;