mysql - 一对多双向映射提示没有默认值错误

Question

我有两个实体类。

@Entity

公共(public)类员工{

@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

公开课技能{

@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;
}

}

当它们都是单向时，我可以保存与技能关联的员工对象。

现在，当我尝试使其成为双向时，我收到 sql 错误，指出字段“skill_id”没有默认值

我不知道我哪里做错了。请您指出。

Answer 1

这里没有双向 OneToMany 关联。您有两个独立的关联映射到同一个连接表。双向关联必须有一侧(在本例中为一侧)，这是关联的反面，这要归功于 mappedBy 属性:

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