如何使用JPA删除联接表中的行 [英] How to delete a row in join table with JPA

问题描述

我有下面的模型:文章可以有一些标签，并且标签可以在某些文章上. 因此，这是3个表的多对多关系:

I have the model below : an article can have some tags and a tag can be on some articles. So it is a many-to-many relationship with 3 tables :

• 文章
• ARTICLE_TAG
• TAG

删除标签时，我要删除:

When I delete a tag, I want to delete :

• TAG中的标签
• 标记和ARTICLE_TAG中标记的文章之间的所有关系

但是我当然不想删除ARTICLE中的文章.

But I don't want to delete the articles in ARTICLE of course.

我该怎么做?

我尝试了一下，但是没用:

I try this, but it doesn't work :

Session session = HibernateUtil.getSessionFactory().getCurrentSession();
for (Article article : tagToDelete.getArticles()) {
    article.getTags().remove(tagToDelete);
}
session.delete(tagToDelete);

谢谢！

@Entity
@Table(name="ARTICLE")
public class Article extends AbstractAuditedEntity {

    @Id
    @Column(name="ID", nullable=false)
    private Long id;

    @ManyToMany
    @JoinTable(name="ARTICLE_TAG", joinColumns=@JoinColumn(name = "ARTICLE_ID"), inverseJoinColumns=@JoinColumn(name = "TAG_ID"))
    private Set<Tag> tags = new HashSet<>();

    public Article() {}

    /** Getters & Setters */
}

@Entity
@Table(name="TAG")
public class Tag {

    @Id
    @Column(name="ID", nullable=false)
    private Long id;    

    @ManyToMany(mappedBy="tags")
    private Set<Article> articles = new HashSet<>();

    public Tag() {}

    /** Getters & Setters */        
}

推荐答案

我尝试删除类似的记录.有效.

I try to delete the records like that. It worked.

将id传递给API，然后删除每个记录.试试吧.

Pass id to API and then it deletes that each record. Try it.

有任何问题，请通知我.

Have any issues please let me know.

@Entity
@Table(name="ARTICLE") 
public class Article {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "article_id")
    private int id;

    @ManyToMany(mappedBy="article")
    private Set<Article_Tag> article_tag = new HashSet<>();

    public Article() {}

    /** Getters & Setters */



@Entity
@Table(name="TAG")
public class Tag {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "tag_id")
    private int id;

    @ManyToMany(mappedBy="tag")
    private Set<Article_Tag> article_tag = new HashSet<>();

    public Tag() {}

    /** Getters & Setters */



@Entity
@Table(name="ARTICLE_TAG")
public class Article_Tag {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private int id;

    @ManyToMany(cascade={CascadeType.PERSIST, CascadeType.DETACH})
    @joinColumn(name = "article_id")
    private Set<Article> articles = new HashSet<>();

    @ManyToMany(cascade={CascadeType.PERSIST, CascadeType.DETACH})
    @joinColumn(name = "tag_id")
    private Set<Tag> tags = new HashSet<>();

    public Article_Tag() {}

    /** Getters & Setters */



public interface Article_TagRepository extends JpaRepository<Article_Tag, Integer>{

    Article_Tag findByArticle(Article id);

    Article_Tag findByTag(Tag id);

}



@RestController
@RequestMapping(value = "/")
public class Article_TagController {

@Autowired
private Article_TagRepository article_tagRepository;

@GetMapping("/delete/article/{id}")
public String DeleteArticleById(@PathVariable("id") Article id) {
    Article_Tag article_tag = article_tagRepository.findByArticle(id);
    Integer article_tag_id = article_tag.getId();
    article_tagRepository.deleteById(article_tag_id);
    return "Article Successfully Deleted !!!";
}

@GetMapping("/delete/tag/{id}")
public String DeleteTagById(@PathVariable("id") Tag id) {
    Article_Tag article_tag = article_tagRepository.findByTag(id);
    Integer article_tag_id = article_tag.getId();
    article_tagRepository.deleteById(article_tag_id);
    return "Tag Successfully Deleted !!!";
}

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