如何在Spring Data JPA中使用額外的列實現多對多關系？

Question

我正在嘗試建立多對多關系。 以下是我要創建的關系：

Heroes表正常保存值，但Hero_DnDClasses表中未寫入任何記錄。

這是我的課程：

英雄

@Entity
@Table(name = "HEROES")
public class Hero {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "HERO_ID")
private Long id;

private Short strength;
private Short dexterity;
private Short constitution;
private Short intelligence;
private Short wisdom;
private Short charisma;
private String name;

@ManyToOne
private Race race;

@OneToMany(mappedBy = "hero")
private List<HeroDnDClasses> heroDnDClasses = new ArrayList<>();

public Hero() {
}

public Hero(Short strength, Short dexterity, Short constitution, Short intelligence, Short wisdom, Short charisma, String name, Race race, List<HeroDnDClasses> heroDnDClasses) {
    this.strength = strength;
    this.dexterity = dexterity;
    this.constitution = constitution;
    this.intelligence = intelligence;
    this.wisdom = wisdom;
    this.charisma = charisma;
    this.name = name;
    this.race = race;
    this.heroDnDClasses = heroDnDClasses;
}

public Long getId() {
    return id;
}

public Short getStrength() {
    return strength;
}

public Short getDexterity() {
    return dexterity;
}

public Short getConstitution() {
    return constitution;
}

public Short getIntelligence() {
    return intelligence;
}

public Short getWisdom() {
    return wisdom;
}

public Short getCharisma() {
    return charisma;
}

public String getName() {
    return name;
}

public Race getRace() {
    return race;
}

public List<HeroDnDClasses> getHeroDnDClasses() {
    return heroDnDClasses;
}

@Override
public String toString() {
    return "Hero{" +
            "id=" + id +
            ", strength=" + strength +
            ", dexterity=" + dexterity +
            ", constitution=" + constitution +
            ", intelligence=" + intelligence +
            ", wisdom=" + wisdom +
            ", charisma=" + charisma +
            ", name='" + name + '\'' +
            ", race=" + race +
            ", HeroDnDClasses=" + heroDnDClasses +
            '}';
}

public static HeroBuilder builder(){
    return new HeroBuilder();
}

public static class HeroBuilder {
    private Short strength;
    private Short dexterity;
    private Short constitution;
    private Short intelligence;
    private Short wisdom;
    private Short charisma;
    private String name;
    private Race race;
    private List<HeroDnDClasses> heroDnDClasses;

    public HeroBuilder setStrength(Short strength) {
        this.strength = strength;
        return this;
    }

    public HeroBuilder setDexterity(Short dexterity) {
        this.dexterity = dexterity;
        return this;
    }

    public HeroBuilder setConstitution(Short constitution) {
        this.constitution = constitution;
        return this;
    }

    public HeroBuilder setIntelligence(Short intelligence) {
        this.intelligence = intelligence;
        return this;
    }

    public HeroBuilder setWisdom(Short wisdom) {
        this.wisdom = wisdom;
        return this;
    }

    public HeroBuilder setCharisma(Short charisma) {
        this.charisma = charisma;
        return this;
    }

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

    public HeroBuilder setRace(Race race) {
        this.race = race;
        return this;
    }

    public HeroBuilder setHeroDnDClasses(List<HeroDnDClasses> heroDnDClasses) {
        this.heroDnDClasses = heroDnDClasses;
        return this;
    }

    public Hero build() {
        return new Hero(strength, dexterity, constitution, intelligence, wisdom, charisma, name, race, heroDnDClasses);
    }
}
}

HeroDnDClasses.java

@Entity
@Table(name = "HERO_DNDCLASSES")
public class HeroDnDClasses implements Serializable {

@Id
@ManyToOne
@JoinColumn(name = "HERO_ID")
private Hero hero;

@Id
@ManyToOne
@JoinColumn(name = "DNDCLASS_ID")
private DnDClass dnDClass;

private Integer level;

public Hero getHero() {
    return hero;
}

public void setHero(Hero hero) {
    this.hero = hero;
}

public DnDClass getDnDClass() {
    return dnDClass;
}

public void setDnDClass(DnDClass dnDClass) {
    this.dnDClass = dnDClass;
}

public Integer getLevel() {
    return level;
}

public void setLevel(Integer level) {
    this.level = level;
}

@Override
public String toString() {
    return "HeroDnDClasses{" +
            "hero=" + hero +
            ", dnDClass=" + dnDClass +
            ", level=" + level +
            '}';
}
}

HeroService.java

@Service
public class HeroService {

private static final Logger LOGGER = LoggerFactory.getLogger(HeroService.class);

@Autowired
HeroRepository heroRepository;

@Autowired
DnDClassService dnDClassService;

@Autowired
RaceService raceService;

public List<Hero> getAllHeroes(){
    return heroRepository.findAll();
}

@Transactional
public void addHero(Hero hero){
    DnDClass newDnDClass = dnDClassService.findDnDClassById(hero.getHeroDnDClasses().get(0).getDnDClass().getId());
    HeroDnDClasses newHeroDnDClasses = new HeroDnDClasses();

    Race newRace = raceService.getRaceById(hero.getRace().getId());
    newHeroDnDClasses.setDnDClass(newDnDClass);
    newHeroDnDClasses.setLevel(hero.getHeroDnDClasses().get(0).getLevel());

    List<HeroDnDClasses> heroDnDClassesList = new ArrayList<>();
    heroDnDClassesList.add(newHeroDnDClasses);

    Hero newHero = Hero.builder().setName(hero.getName())
            .setStrength(hero.getStrength())
            .setDexterity(hero.getDexterity())
            .setConstitution(hero.getConstitution())
            .setIntelligence(hero.getIntelligence())
            .setWisdom(hero.getWisdom())
            .setCharisma(hero.getCharisma())
            .setRace(newRace)
            .setHeroDnDClasses(heroDnDClassesList)
            .build();

    heroRepository.save(newHero);
}

public Hero findHeroById(Long id){
    return heroRepository.findById(id);
}

public Hero findHeroByName(String name){
    return heroRepository.findByName(name);
}
}

我遵循了一些教程，但是我的代碼雖然可以運行，但似乎無法正常工作。 請告訴我是否需要我發布其他課程。 提前致謝。

Answer 1

1）設置級聯：

@OneToMany(mappedBy = "hero", cascade = {CascadeType.PERSIST, CascadeTYPE.MERGE})
private List<HeroDnDClasses> heroDnDClasses = new ArrayList<>();

2）您忘記在鏈接實體上設置英雄參考：

newHeroDnDClasses.setDnDClass(newDnDClass);
newHeroDnDClasses.setLevel(hero.getHeroDnDClasses().get(0).getLevel());
..
Hero newHero = Hero.builder().setName(hero.getName())
..
newHeroDnDClasses.setHero(newHero);

現在雙方都有引用， save操作也將級聯到鏈接表。