How to delete a row in join table with JPA

Question

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 */        
}

Answer 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.