问题
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 :
- ARTICLE
- ARTICLE_TAG
- TAG
When I delete a tag, I want to delete :
- the tag in TAG
- all relations between the tag and the articles tagged in ARTICLE_TAG
But I don't want to delete the articles in ARTICLE of course.
How can I do that ?
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);
Thanks !
@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 */
}
回答1:
Found the solution. On delete, we need to make sure not to cascade the delete to the Article, and vice-versa.
@ManyToMany(cascade={PERSIST, DETACH})
@JoinTable(name="ARTICLE_TAG",
joinColumns=@JoinColumn(name = "ARTICLE_ID"),
inverseJoinColumns=@JoinColumn(name = "TAG_ID"))
private Set<Tag> tags = new HashSet<>();
My problem was using CascadeType.All
, which by default includes CascadeType.REMOVE
, which will cascade the deletion of an article to the Tags it contains.
You can also add cascade={PERSIST, DETACH}
to your Tag entity to prevent the deletion of a Tag to delete its associated Article.
回答2:
I try to delete the records like that. It worked.
Pass id
to API and then it deletes that each record. Try it.
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 !!!";
}
来源:https://stackoverflow.com/questions/43235303/how-to-delete-a-row-in-join-table-with-jpa