为什么JpaRepository在保存实体时尝试为空FK密钥创建实体？

Question

我的Person表中有字段country（FK，可以为空）。当我试图用空的国家/地区值保存Person时，我将收到一条错误消息500和消息

2020-01-30 15:16:37.277警告10524---[nio-8098-exec-1]o.h.发动机。jdbc。spi。SqlExceptionHelper:SQL错误：0，SQLState:23502 2020-01-30 15:16:37.277错误10524---[nio-8098-exec-1]o.h.engine。jdbc。spi。SqlExceptionHelper:öзББСА：зггбббббббббббббббббббббббббббб107。2020-01-30 15:16:37.299错误10524---[nio-8098-exec-1]o.z.问题。Spring常见的AdviceTraits:内部服务器错误

组织。springframework。刀。DataIntegrityViolationException:无法执行语句；SQL[n/a]；约束[null]；嵌套的异常是org。冬眠例外ConstraintViolationException:无法执行语句

粗差交易：

错误：“代码”列中的null值打破了非null限制详细信息：错误字符串包含（42，null，null，null）。

Person.java

@Entity
@Table(name = "t_person")
@Data
public class Person {
    @Id
    @Column(name = "person_id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    private String surname;
    private String name;
    private String patronymic;

    @Column(name = "surname_rus")
    private String surnameRus;

    @Column(name = "name_rus")
    private String nameRus;

    @Column(name = "surname_eng")
    private String surnameEng;

    @Column(name = "name_eng")
    private String nameEng;

    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "country_id")
    private Country country;

    private String settlement;
    private String occupation;

    @ManyToMany
    @JoinTable(
            name = "person_link",
            joinColumns = @JoinColumn(name = "person_id", referencedColumnName = "person_id"),
            inverseJoinColumns = @JoinColumn(name = "link_id", referencedColumnName = "link_id"))
    private List<UrlLink> linkList;

    @ManyToMany
    @JoinTable(
            name = "org_actor",
            joinColumns = @JoinColumn(name = "actor_id", referencedColumnName = "person_id"),
            inverseJoinColumns = @JoinColumn(name = "org_id", referencedColumnName = "org_id"))
    private List<Org> orgList;

    private String description;

    @ManyToMany
    @JoinTable(
            name = "person_hashtag",
            joinColumns = @JoinColumn(name = "person_id", referencedColumnName = "person_id"),
            inverseJoinColumns = @JoinColumn(name = "hashtag_id", referencedColumnName = "hashtag_id"))
    private List<HashTag> hashtagList;


************
Country.java

@Entity
@Table(name="t_country")
@Data

public class Country {
    @Id
    @Column(name = "country_id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)

    private Integer id;
    private String code;
    private String name;
}

create table t_country
(
    country_id serial  not null
        constraint t_country_pkey
            primary key,
    code       char(3) not null
        constraint unique_constr_code
            unique,
    name       text
        constraint unique_constr_name
            unique,
    miscellany text,
    constraint constr_name
        unique (code, name)
);

如何用空的国家保存个人实体？

Answer 1

在您的国家/地区数据库表定义中，字段代码定义为

code
   char(3) not null
    constraint unique_constr_code
        unique,

表示在db级别上存在非空约束。

这就是为什么你不能用一个空旷的国家来拯救一个人。

因此，即使java代码中没有NOTNULL约束，db也会拒绝该值。也许您在删除java代码中的NOTNULL约束后忘记了迁移db？