Spring Data JPA: How to set 2 foreign keys on the child entity during insert

Question

I am new to Spring JPA and I am having some trouble with setting foreign keys on an entity when inserting a row.

I have the following entities

@Entity
public class Department {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    private String departmentName;

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "department_id")
    List<Employee> employees;
}

@Entity
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    private String employeeName;

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "employee_id")
    List<Role> roles;

    @ManyToOne
    @JoinColumn(name = "department_id", insertable = false, updatable = false)
    private Department department;
}

@Entity
public class Role {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    private String roleName;

    @ManyToOne
    @JoinColumn(name = "employee_id", insertable = false, updatable = false)
    private Employee employee;

    @ManyToOne
    @JoinColumn(name = "department_id", insertable = false, updatable = false)
    private Department department;
}

And here is the Department Repository:

@Repository
public interface DepartmentRepository extends JpaRepository<Department, Integer> {

    Department findById(long id);

}

With this approach, the department_id in the employee table and the employee_id in the role table is set correctly when I save a Department object using departmentRepository.save(department) .

But I also want it to set the department_id in the role table. How can this be achieved? Currently the relationship Department and Role is indirect (ie it is through Employee) but would I have to create a direct relationship between the 2 entities? I am not sure how to achieve this though. Any input will be appreciated.

Edit:

I want to model the relationship in this Entity Relationship diagram

Answer 1

As I see that you already using

@OneToMany(cascade = CascadeType.ALL)

So you knew that every update on Department with list Employee can do "many" things.

So Employee do the same to Roles (your list) but the magic auto save/update won't help.

Condition now:

• Save action in repo
• List of Employee
• List of Role in employee (each object don't have Department Id)

As I understand:

You have Department that 1-n to Employee (Employee can only have 1 Department)

Employee can have many Role

As normal logic: Deparment 1-n Employee 1-n Roles

But some how you want Role have object of Department also.

So my first suggestion is change of logic code.

And second: a way to solve your problem!

Create Department

when add Role to Employee, please access and add deparment_id also. (Department save List Employee, when save Employee - list Roles also save with same logic, just make sure to add it)