Question

让我们有三个JPA实体。一个Person和两个一对多关系。当我尝试保存Person AD_P_ID和AC_P_ID外键时总是为空。这些字段的期望值为个人ID。我在做什么错了？

Person.java：它与Account和Address Entity类包含一对多关系

@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;
    }
}

Account.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;
    }
}

Address.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;
    }
}

用于保存人员的代码：

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

对于每个Address和Account实体，您需要设置Person实体。为了使休眠状态将ID保存在子级中，这是强制性的：

Person p = new Person();

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

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

Answer 2

@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。您可以按照Maciej的建议手动进行设置，但是会添加一些锅炉代码。

要自动将父级引用设置为其子级，必须通过以下方式定义关系的所有者。

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

@OneToMany关系不会将父级的主键保存在子级表中

2 个答案: