why employee_id and department_id not update automatic in database Hibernate jpa

few days back i starting learning hibernate JPA but i am unable to find solution of given problem below

My Project consist three class employee ,phone ,department by seeing code you can easily understand what i am doing .

Main problem raise when i try to save this data into database using spring boot controller it showing null value in column . In employee table department_id is null(not automatic update using cascade.All) same in phone table employee_id is null.

I do not want update manually .is their any way so dep_id and emp_id automatic update to foreign key table .

{
"name":"CSE",
 "employees":[
     {
         "name":"Welcome",
         "age":23,
         "phones":[{"number":1234567890},{"number":1234567890}]
     },
     {
         "name":"back",
         "age":25,
         "phones":[{"number":1234567890},{"number":1234567890}]
     }
     
 ]

}

package com.example.entity;

import javax.persistence.*;
import java.util.List;

@Entity
@Table(name = "employee")
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    private String name;

    private int age;

    @ManyToOne
    @JoinColumn(name = "department_id")
    private Department department;

    @OneToMany(mappedBy = "employee", cascade=CascadeType.ALL)
    private List<Phone> phones;

    // getters and setters...
}

package com.example.entity;

import javax.persistence.*

@Entity
public class Phone {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    private String number;

    @ManyToOne
    @JoinColumn(name = "employee_id")
    private Employee employee;

    // getters and setters...
}

package com.example.entity;

import javax.persistence.*;
import java.util.List;

@Entity
public class Department {

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

    private String name;

    @OneToMany(mappedBy = "department",cascade = CascadeType.ALL)
    private List<Employee> employees;
}

dept table  in database
id   name
1    CSE

employee table 
id  name     age department_id
1.  welcome   23.    null
2.  back.     25.    null

phone table
id  number    employee_id
1.  1234567890. null
2.  1234567890.  null
3.  1234567890   null
4.  1234567890.  null

Why employee_id and department_id not updating automatic in cascade All

Controller class
package com.example.controller;

import com.example.dao.DepRepo;
import com.example.dao.EmployeeRepo;
import com.example.dao.PhoneRepo;
import com.example.entity.Department;
import com.example.entity.Employee;
import com.example.service.FakeService;
import io.micronaut.http.HttpResponse;
import io.micronaut.http.HttpStatus;
import io.micronaut.http.annotation.Body;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Post;
import jakarta.inject.Inject;

@Controller("/dummy")
public class DummyController {

    @Inject
    FakeService fakeService;
    @Inject
    PhoneRepo phoneRepo;
    @Inject
    EmployeeRepo employeeRepo;
    @Inject
    DepRepo depRepo;


    @Get ("/")
    public String fun(){

        fakeService.fun();
        return "welcome back";
    }

    @Post("/add")
    public HttpResponse<?> fun(@Body Department dep){
        System.out.println(dep);
        depRepo.save(dep);
        return HttpResponse.status(HttpStatus.ACCEPTED).body("data add successfully");
    }
}