Java org.postgresql.util.PSQLException:错误：列“中的值为空”；类别“U id”；违反非空约束

我有一个奇怪的问题：我试图在我的数据库中保存一个用户，这个用户有一个技能列表。这些技能已经存在于具有链接类别的数据库中，并且类别具有链接域。结构如下所示：

当我打印申请人的技能列表时，我有以下几点：

skills=[Skill{categories=[Category{domains=[Domain{id=4, name=DevOps}], id=13, name=BackEnd}], id=23, name=Java}, Skill{categories=[Category{domains=[Domain{id=4, name=DevOps}], id=13, name=BackEnd}], id=24, name=C}],

以下表格显示了申请人与技能之间的联系：

但当我试图保存申请者时，我有一个Détail：失败的行包含（23，null，null，499）。有人能给我解释一下吗？我正在使用jpa注释开发一个spring应用程序

编辑1：

应用内容：

@Entity
@Table(name = "ATS_APPLICANT")
public class ApplicantEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "home", unique = false, nullable = true)
    private Boolean home;

    @Column(name = "anonymous", unique = false, nullable = true)
    private Boolean anonymous;

    @Enumerated(EnumType.STRING)
    @Column(name = "job_type")
    private JobType jobType;

    @Column(name = "min_salary", unique = false, nullable = true)
    private Integer minSalary;

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(unique = true)
    private UserEntity user;

    @OneToMany(targetEntity = ApplicantWorkExperienceEntity.class, cascade = CascadeType.ALL)
    private List<ApplicantWorkExperienceEntity> applicantWorkExperiences = new ArrayList<ApplicantWorkExperienceEntity>();

    @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.MERGE)
    @JoinTable(name = "ATS_APPLICANT_SKILL", joinColumns = @JoinColumn(name = "applicant_id", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "skill_id", referencedColumnName = "id"))
    private List<SkillEntity> skills = new ArrayList<SkillEntity>();

    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "ATS_APPLICANT_LOCATION", joinColumns = @JoinColumn(name = "applicant_id", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "location_id", referencedColumnName = "id"))
    private List<LocationEntity> locations = new ArrayList<LocationEntity>();

---

通过在skills上使用@ElementCollection注释，我成功了。

您应该填写空列{category\u id，domain\u id}因为它没有空的约束。是的，我知道这是我的问题，但当我向申请人添加一项技能时，它应该是自动的。表格可以找到申请人的id和技能的id，但不能找到已经存在的类别的id。您应该添加一些与您的问题相关的代码，以便我们可以提供帮助。@LKTN.25刚刚添加了实体，请查看编辑。尝试从映射注释中删除

referencedColumnName=“id”

。也请添加DomainEntity

@Entity
@Table(name = "ATS_SKILL")
public class SkillEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @NotNull
    @Size(min = 1, max = 42)
    @Column(name = "name", length = 42, nullable = false, unique = true)
    private String name;

    @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinTable(name = "ATS_SKILL_CATEGORY", joinColumns = @JoinColumn(name = "skill_id", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "category_id", referencedColumnName = "id"))
    private List<CategoryEntity> categories = new ArrayList<CategoryEntity>();

@Entity
@Table(name = "ATS_CATEGORY")
public class CategoryEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @NotNull
    @Size(min = 1, max = 42)
    @Column(name = "name", length = 42, nullable = false, unique = true)
    private String name;

    @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinTable(name = "ATS_CATEGORY_DOMAIN", joinColumns = @JoinColumn(name = "category_id", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "domain_id", referencedColumnName = "id"))
    private List<DomainEntity> domains = new ArrayList<DomainEntity>();

@Entity
@Table(name = "ATS_DOMAIN")
public class DomainEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @NotNull
    @Size(min = 1, max = 42)
    @Column(name = "name", length = 42, nullable = false, unique = true)
    private String name;