为什么employee_id和department_id不会在数据库Hibernate jpa中自动更新

Question

几天前我开始学习休眠 JPA，但我无法找到以下给定问题的解决方案

我的项目由三类员工、电话、部门组成，通过查看代码您可以轻松了解我在做什么。

当我尝试使用 Spring Boot 控制器将此数据保存到数据库中时，出现的主要问题是它在列中显示空值。在员工表中，department_id 为空（不是使用 cascade.All 自动更新），在电话表中，employee_id 为空。

我不想手动更新。他们有什么办法让 dep_id 和 emp_id 自动更新到外键表。

{
"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

为什么employee_id 和department_id 没有在级联中自动更新全部

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");
    }
}

Answer 1

您的 Hibernate 映射表明关系由关联的“多”方映射：

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

所以 Hibernate 在员工实体中查找“部门”的值，结果为空（因为 JSON 数据中没有值）

所以尝试删除 mappedBy 以告诉 Hibernate 关系映射在“一”侧