JPA - Foreign Key Constraint problem when deleting entity even after removing connected entity-CodePudding

I have a News entity that has the following fields:

    @ManyToMany(mappedBy = "news")
    @LazyCollection(LazyCollectionOption.FALSE)
    private List<Category> categories;

    @LazyCollection(LazyCollectionOption.FALSE)
    @OneToMany(mappedBy = "news", cascade = CascadeType.REMOVE)
    @JsonIgnore
    private List<Comment> comments;

    @ManyToMany(mappedBy = "newsVoted")
    @JsonIgnore
    private Collection<Session> sessionsVoted;

My Category entity has those fields:

    @Id
    @GeneratedValue
    private long id;

    private String name;

    private int priority;

    @LazyCollection(LazyCollectionOption.FALSE)
    @ManyToMany
    @JsonIgnore
    private List<News> news;

    private boolean visible;

I am trying to delete one News entry without removing connected Categories.

My code looks like this:

                news.setComments(new ArrayList<Comment>());
                news.setCategories(new ArrayList<Category>());
                news.setSessionsVoted(new ArrayList<Session>());

                news.getComments().forEach(comment -> comment.setNews(null));
                news.getCategories().forEach(category -> category.setNews(null));
                news.getSessionsVoted().forEach(session -> session.setNewsVoted(null));

                newsFacade.save(news);
                news.getComments().forEach(comment -> commentFacade.save(comment));
                news.getCategories().forEach(category -> categoryFacade.save(category));
                news.getSessionsVoted().forEach(session -> sessionFacade.save(session));

                em.flush();

                newsFacade.delete(news);

I tried to detach all Categories from News. However, when I execute this, I get the following Error:

Caused by: org.postgresql.util.PSQLException: ERROR: update or delete on table "news" violates foreign key constraint "fkhik32gpatwh82fuds49l7goo3" on table "category_news"
  Detail: Key (id)=(5) is still referenced from table "category_news".
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2505)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2241)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:310)
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:447)
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:368)
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:158)
    at org.postgresql.jdbc.PgPreparedStatement.executeUpdate(PgPreparedStatement.java:124)
    at sun.reflect.GeneratedMethodAccessor82.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.postgresql.ds.PGPooledConnection$StatementHandler.invoke(PGPooledConnection.java:428)
    at com.sun.proxy.$Proxy132.executeUpdate(Unknown Source)
    at org.jboss.jca.adapters.jdbc.WrappedPreparedStatement.executeUpdate(WrappedPreparedStatement.java:537)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:175)
    ... 67 more

It seems like this category is still conected to the news. I wonder how

CodePudding user response：

After executing these statements

news.setComments(new ArrayList<Comment>());
news.setCategories(new ArrayList<Category>());
news.setSessionsVoted(new ArrayList<Session>());

aren't these statements just iterating over empty lists?

news.getComments().forEach(comment -> comment.setNews(null));
news.getCategories().forEach(category -> category.setNews(null));
news.getSessionsVoted().forEach(session -> session.setNewsVoted(null));