SpringBoot JPA 中的实体映射错误。实体正在创建，但未添加 foreign_key

Question

我正在学习 SpringBoot，为此我试图在一个问题的帮助下实现我学到的东西。

这是基本问题：我们有 2 个实体：

Team: id, name Developer: id, team_id, name, phone number

Create team API : This api takes in a team and a list of developers to be mapped with this team, and is expected to create the corresponding entries in the database.
Sample request: {"team": {"name": "claims"}, "developers": [{"name": "someone", "phone_number": "9999999999"}, {"name": "somebody", "phone_number": "9111111111"}]}

我使用了这些实体：

**Employee.java**
package com.PagerDuty.PagerDutyManager.Employee;

import com.PagerDuty.PagerDutyManager.Team.Team;
import com.fasterxml.jackson.annotation.JsonBackReference;

import javax.persistence.*;
import javax.validation.constraints.*;

@Entity
public class Employee {

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

    @NotNull
    @NotBlank(message="Invalid Name")
    private String name;

    @Column(columnDefinition="varchar(10)", unique = true)
    @NotBlank(message = "Phone_number Number Required!")
    @Pattern(regexp="(^$|[0-9]{10})", message="Invalid Phone_number Number")
    private String phone_number;

    @ManyToOne
    @JoinColumn(referencedColumnName = "id")
    @JsonBackReference
    private Team team;

    public Employee(){}

    public Employee(Long id,
                    @NotNull @NotBlank(message = "Invalid Name") String name,
                    @NotBlank(message = "Phone_number Number Required!") @Pattern(regexp = "(^$|[0-9]{10})", message = "Invalid Phone_number Number") String phone_number, String teamId) {
        this.id = id;
        this.name = name;
        this.phone_number = phone_number;
        this.team = new Team(teamId, "");
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPhone_number() {
        return phone_number;
    }

    public void setPhone_number(String phone_number) {
        this.phone_number = phone_number;
    }

    public Team getTeam() {
        return team;
    }

    public void setTeam(Team team) {
        this.team = team;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", phone_number='" + phone_number + '\'' +
                ", team=" + team +
                '}';
    }
}

**Team.java**
package com.PagerDuty.PagerDutyManager.Team;

import com.PagerDuty.PagerDutyManager.Employee.Employee;
import com.fasterxml.jackson.annotation.JsonBackReference;
import com.fasterxml.jackson.annotation.JsonManagedReference;

import javax.persistence.*;
import javax.validation.constraints.Email;
import javax.validation.constraints.NotBlank;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Pattern;
import java.util.List;

@Entity
public class Team {

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

    @NotNull
    @NotBlank(message="Invalid Name")
    @Column(unique = true)
    private String name;

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

    public Team(){}

    public Team(String id,
                @NotNull @NotBlank(message = "Invalid Name") String name) {
        this.id = Long.parseLong(id);
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<Employee> getEmployees() {
        return employees;
    }

    public void setEmployees(List<Employee> employees) {
        this.employees = employees;
    }

    @Override
    public String toString() {
        return "Team{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", employees=" + employees +
                '}';
    }
}

我已经完成了上面的示例请求，但是无法建立关系。

Employees are added successfully while adding the team. Add team: Here RequestBody is to handle the body properly. // Please suggest a better way of doing the requestBody Structure Handling```

**AddTeam Controller Function**
@PostMapping("/team")
    public void addTeam(@RequestBody RequestCustomBody body){
        System.out.println("Add team request body "+body.toString());
        Team team = body.getTeam();
        team.setEmployees(body.getDevelopers());
        System.out.println("New Team "+team.toString());
        teamService.addTeam(team);
    }

**AddTeam Service Function**
public void addTeam(Team team){
        teamRepository.save(team);
    }

但是我只添加了 Employee 和 Team 而没有添加外键。

任何人都请帮助我我做错了什么。并且说说做事的好方法。

Answer 1

你需要做 body.getDevelopers().forEach(d -> d.setTeam(team)).

为什么？在 JPA 术语中，Employee 是关系的拥有方。这是 counter-intuitive（在日常使用中可以说“一个团队有名员工”）。但在 JPA 中，拥有方是（在此简化）拥有外键的一方（使用关系 table 时除外）。另一面，相反，是在关系注释中具有 mappedBy 属性的那一面。

最重要的是，您需要在 JPA 中从拥有方设置关系。你甚至可以跳过设置team.employees，从数据库的角度来看，效果是一样的。

SpringBoot JPA 中的实体映射错误。实体正在创建，但未添加 foreign_key

Error in Entity Mapping in SpringBoot JPA. Entities are creating but foreign_key is not added

java

sql

jpa

relational-database

spring-boot

我已经完成了上面的示例请求，但是无法建立关系。