java - 如何级联持久化 @ManyToOne 关系(TransientPropertyValueException)？

Question

我想使用hibernate创建数据库映射:每个Person可能只有一个Address，但可以分配相同的地址多人(例如家庭成员)。

以下映射不起作用:

@Entity
public class Person {
    @ManyToOne
    @JoinColumn(name="fk_address_id", foreignKey = @ForeignKey(name="fk_addres"))
    private Address address;
}


@Entity
public class Address {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String city;
    private int zip;
    private String street;

    @OneToMany(mappedBy = "address", cascade = {CascadeType.ALL})
    private Set<Person> persons;
}


@Transactional
public void create() {
    Person person = new Person();
    Address address = new Address();
    address.setStreet("test 1");
    address.setCity("test");
    address.setZip(123);
    person.setAddress(address);
    dao.save(person);
}

结果:

org.hibernate.TransientPropertyValueException: object references an unsaved transient instance - save the transient instance before flushing : Person.address -> Address

为什么我会遇到此异常，如何防止它发生？我认为由于级联，地址应该自动保存？

Answer 1

添加@Cascade({CascadeType.MERGE})至private Set<Person> persons;或从 ALL 更改至MERGE 。问题是您正在对人员进行更改，并且在保存地址之前没有保存它们。合并级联将为您完成此操作。