Question

我在我的（Spring Framework + Spring Data + Hibernate JPA）项目中有一个单向的OneToMany JPA实体映射。实体类类似于以下代码。（为简洁起见，我删除了无关的类成员。）

@Entity
@Table(name = "employees")
class Employee{
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   @Column(name = "id")
   private Integer id;

   @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
   @JoinColumn(name = "employee_id")
   private List<DepartmentAssignment> departmentAssignments = new ArrayList<>();
}

@Entity
@Table(name = "department_assignments")
class DepartmentAssignment{
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   @Column(name = "id")
   private Integer id;

   @NotNull
   @Column(name = "employee_id")
   private Integer employeeId;

   @NotNull
   @Column(name = "department_id")
   private Integer departmentId;
}

@Entity
@Table(name = "departments")
class Department{
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   @Column(name = "id")
   private Integer id;       
}

并且，在我的一个服务类中有一个从Employee中删除DepartmentAssignment的方法，如下所示。

public Employee deleteDepartmentAssignment(Integer empId, Integer deptAssignmentId) {
        Employee employee = employeeRepository.findOne(empId);
        if(employee != null) {
            for ( DepartmentAssignment da : employee.getDepartmentAssignments()) {
                if(da.getId().equals(deptAssignmentId)) {
                    employee.getDepartmentAssignments().remove(da);
                    employee = employeeRepository.save(employee);
                    break;
                }
            }
        }

        return employee;
    }

但是，调用上面的方法会给我一个错误：org.hibernate.exception.ConstraintViolationException，在SQL日志中，我可以看到事件的最后一个SQL语句出现Column 'employee_id' cannot be null错误。

有人可以告诉我这里我做错了什么以及如何解决这个问题？

Answer 1

您无需添加

@NotNull
@Column(name = "employee_id")
private Integer employeeId;

如果您使用Employee，请

到@JoinColumn(name = "employee_id")。尝试删除它。

Answer 2

您可以尝试以下操作，不确定为什么在对象中使用plain id。那不是对象关系映射。有关详细信息，请参阅Hibernate triggering constraint violations using orphanRemoval

@Entity
@Table(name = "employees")
class Employee{
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Integer id;

   @OneToMany(cascade = CascadeType.ALL, mappedBy = "employee", orphanRemoval = true)
   private List<DepartmentAssignment> departmentAssignments = new ArrayList<>();
}

@Entity
@Table(name = "department_assignments")
class DepartmentAssignment{
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Integer id;

   @ManyToOne(optional=false)
   private Employee employee;

   @ManyToOne(optional=false)
   private Department department;
}

@Entity
@Table(name = "departments")
class Department{
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Integer id;       
}

Answer 3

您必须查看 .hbm.xml 文件，并且应该将您的实体映射到此文件中你可以看看这个例子

http://www.mkyong.com/hibernate/hibernate-one-to-many-relationship-example/

我希望它对你有用。

Answer 4

尝试删除

cascade = CascadeType.ALL

但我不是100％肯定..

Spring Framework + Spring Data + Hibernate Jpa OneToMany子删除失败

4 个答案: