一对多双向映射抱怨没有默认值错误

Question

我有两个实体类。

@Entity

公共类Employee {

@Id
@Column(name = "employee_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private String name;
@OneToMany(cascade = CascadeType.ALL)
@JoinTable(name = "employee_skill", joinColumns = @JoinColumn(referencedColumnName = "employee_id"), inverseJoinColumns = @JoinColumn(referencedColumnName = "skill_id"))
private Collection<Skill> listSkill;
public Integer getId() {
    return id;
}
public void setId(Integer id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public Collection<Skill> getListSkill() {
    return listSkill;
}
public void setListSkill(Skill skill) {
    if (listSkill == null) {
        listSkill = new ArrayList<Skill>();
    }
    listSkill.add(skill);
}

}

@Entity

公共类Skill {

@Id
@Column(name = "skill_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private String name;
@ManyToOne(cascade = CascadeType.ALL)
@JoinTable(name = "employee_skill", joinColumns = @JoinColumn(referencedColumnName = "skill_id", insertable = false, updatable = false), inverseJoinColumns = @JoinColumn(referencedColumnName = "employee_id", insertable = false, updatable = false))
private Employee employee;
public Integer getId() {
    return id;
}
public void setId(Integer id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}   

public Employee getEmployee() {
    return employee;
}
public void setEmployee(Employee employee) {
    this.employee = employee;
}

}

当两者都是UNI-Directional时，我可以保存与技能关联的员工对象。

现在，当我试图使它双向，我得到sql错误说，Field 'skill_id' doesn't have a default value

我不知道我哪里做错了。

Answer 1

这里没有双向的onetmany关联。有两个独立的关联映射到同一个连接表。由于mappedBy属性

，双向关联必须有一个侧(在本例中是单侧)是关联的逆侧:

@OneToMany(cascade = CascadeType.ALL, mappedBy = "employee")
private Collection<Skill> listSkill;