@Entity(name = "Post")
    @Table(name = "post")
    public static class Post {

        @Id
        @GeneratedValue
        private Long id;

        private String title;

        public Post() {}

        public Post(String title) {
            this.title = title;
        }

        @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
        @OrderColumn(name = "entry")
        private List<PostComment> comments = new ArrayList<>();

        public Long getId() {
            return id;
        }

        public void setId(Long id) {
            this.id = id;
        }

        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        public List<PostComment> getComments() {
            return comments;
        }
    }

    @Entity(name = "PostComment")
    @Table(name = "post_comment")
    public static class PostComment {

        @Id
        @GeneratedValue
        private Long id;

        private String review;

        public PostComment() {}

        public PostComment(String review) {
            this.review = review;
        }

        public Long getId() {
            return id;
        }

        public void setId(Long id) {
            this.id = id;
        }

        public String getReview() {
            return review;
        }

        public void setReview(String review) {
            this.review = review;
        }

        @Override
        public String toString() {
            return "PostComment{" +
                    "id=" + id +
                    ", review='" + review + '\'' +
                    '}';
        }
    }

@Test
    public void testLifecycle() {
        doInJPA(entityManager -> {
            Post post = new Post("First post");

            post.getComments().add(new PostComment("My first review"));
            post.getComments().add(new PostComment("My second review"));
            post.getComments().add(new PostComment("My third review"));

            entityManager.persist(post);
            entityManager.flush();

            LOGGER.info("Remove head");
            PostComment deletedComment = post.getComments().remove(0);
            LOGGER.info("Deleted {}", deletedComment);
        });
    }

insert into post_comment (review, id) values ('My first review', 2)
insert into post_comment (review, id) values ('My second review', 3)
insert into post_comment (review, id) values ('My third review', 4)
insert into post_post_comment (Post_id, entry, comments_id) values (1, 0, 2)
insert into post_post_comment (Post_id, entry, comments_id) values (1, 1, 3)
insert into post_post_comment (Post_id, entry, comments_id) values (1, 2, 4)
- Remove head
- Deleted PostComment{id=2, review='My first review'}
delete from post_post_comment where Post_id=1 and entry=2
update post_post_comment set comments_id=3 where Post_id=1 and entry=0
SQL Error: -104, SQLState: 23505
integrity constraint violation: unique constraint or index violation; UK_GB03LQUKC5JC1U847L17M311Q table: POST_POST_COMMENT