SpringBootJPA中的物體映射錯誤。物體正在創建，但未添加foreign_key

我正在學習 SpringBoot，為此我嘗試在問題的幫助下實作我所學的知識。

這是基本問題：我們有 2 個物體：

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"}]}

我使用了這些物體：

**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  
                '}';
    }
}

我已經完成了上述示例請求，但無法建立關系。

添加團隊時已成功添加員工。 添加團隊：這里的RequestBody是正確處理body。 //請提出更好的 requestBody 結構處理方法```

**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);
    }

但我只添加了員工和團隊，但沒有添加外鍵。

任何人請幫助我我做錯了什么。并告訴你做事的好方法。

uj5u.com熱心網友回復：

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

為什么？在 JPA 術語中，員工是關系的擁有方。這是違反直覺的（就像在日常使用中可以說“一個團隊有員工”）。但是在 JPA 中，擁有方是（在這里簡化）具有外鍵的一方（使用關系表時例外）。另一面，相反，是mappedBy在關系注釋中具有屬性的那一面。

最重要的是，您需要在 JPA 中從擁有方設定關系。您甚至可以跳過設定team.employees，從資料庫的角度來看，效果是一樣的。

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