ManyToMany：MappingException：无法确定类型：java.util.List

Question

我有一些桌子：

简介 : id_profil, ...

经验 : id_experience, id_profil#, ...

COMPETENCE_LEVEL : id_competence_level, 级别, ...

一个个人资料可以有很多经验和很多COMPETENCE_LEVEL .

一个经验可以有很多COMPETENCE_LEVEL.

一个COMPETENCE_LEVEL涉及很多经验.

所以，对我来说，在 EXPERIENCE 和 COMPETENCE_LEVEL 之间，这是一个 (n-p) ManyToMany 关系。

我试过了：

PROFIL.java:

@Entity
@Table(name="profil")
public class Profil {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(name="id_profil")
    private Long idProfil;

    public Profil() {
        super();
    }

    public Long getIdProfil() {
        return idProfil;
    }

    public void setIdProfil(Long idProfil) {
        this.idProfil = idProfil;
    }

    @Override
    public String toString() {
        //[...]
    }

}

EXPERIENCE.java:

@Entity
@Table(name="experience")
public class Experience {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(name="id_experience")
    private Long idExperience;

    @ManyToOne
    @JoinColumn(name="id_profil")
    private Profil idProfil;

    private List<CompetenceLevel> competenceLevels;

    public Experience() {
        super();
        idProfil = new Profil();
    }

    public Long getIdExperience() {
        return idExperience;
    }

    public void setIdExperience(Long idExperience) {
        this.idExperience = idExperience;
    }

    public Profil getIdProfil() {
        return idProfil;
    }

    public void setIdProfil(Profil idProfil) {
        this.idProfil = idProfil;
    }

    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "experience_competence_level", joinColumns = @JoinColumn(name = "id_experience", referencedColumnName = "id_experience"), inverseJoinColumns = @JoinColumn(name = "id_competence_level", referencedColumnName = "id_competence_level"))
    public List<CompetenceLevel> getCompetenceLevels() {
        return competenceLevels;
    }

    public void setCompetenceLevels(List<CompetenceLevel> competenceLevels) {
        this.competenceLevels = competenceLevels;
    }

    @Override
    public String toString() {
        // [...]
    }

}

COMPETENCE_LEVEL.java:

@Entity
@Table(name="competence_level")
public class CompetenceLevel {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(name="id_competence_level")
    private Long idCompetenceLevel;

    @OneToOne
    @JoinColumn(name="id_level")
    private Level level;

    @OneToOne
    @JoinColumn(name="id_profil")
    private Profil profil;

    private List<Experience> experiences;

    public CompetenceLevel() {
        super();
    }

    public Long getIdCompetenceLevel() {
        return idCompetenceLevel;
    }

    public void setIdCompetenceLevel(Long idCompetenceLevel) {
        this.idCompetenceLevel = idCompetenceLevel;
    }

    public Level getLevel() {
        return level;
    }

    public void setLevel(Level level) {
        this.level = level;
    }

    public Profil getProfil() {
        return profil;
    }

    public void setProfil(Profil profil) {
        this.profil = profil;
    }

    @ManyToMany(mappedBy = "competenceLevels")
    public List<Experience> getExperiences() {
        return experiences;
    }

    public void setExperiences(List<Experience> experiences) {
        this.experiences = experiences;
    }

    @Override
    public String toString() {
        // [...]
    }

}

所以，我有这个错误：

org.hibernate.MappingException: Could not determine type for: java.util.List, at table: competence_level, for columns: [org.hibernate.mapping.Column(experiences)]

我不明白为什么。我遵循这个教程：https://hellokoding.com/jpa-many-to-many-relationship-mapping-example-with-spring-boot-maven-and-mysql/

你有想法吗？谢谢。

Answer 1

原因很简单：不要在同一个持久化中混合字段和方法注释class。

Hibernate 在这里产生了一个不清楚的错误。如果不面对错误，很难找出错误的原因。

Answer 2

在您的代码中，您混合了字段访问和属性访问。参见 this answer。

我宁愿只使用其中一种可能性。我使用字段注释，就像您对 idProfil.

所做的那样

在 Nicholas S. Williams 的书 "Professional Java for Web Applications" 中（非常非常好）我发现了这个：

You should never mix JPA property annotations and JPA field annotations in the same entity. Doing so results in unspecified behaviour and is very likely to cause errors.

为了清楚起见，我不会写这个

@ManyToOne
@JoinColumn(name="id_profil")
private Profil idProfil;
// better:
// private Profil profil;

ManyToMany：MappingException：无法确定类型：java.util.List

ManyToMany : MappingException: Could not determine type for: java.util.List

java

many-to-many

hibernate