Hibernate update non-reference fields of object

Question

I want to develop a CMS using Java, Spring Data/ MVC/ DI , Hibernate defining REST-like API.

I have the following model entities:

• there are multiple Article s
• each article has multiple Section s
• each section can have subsections and / or Item

All these entities have properties of their own (eg name, type etc.), but as it is obvious they refer to their aggregated entities. I need to defined CRUD API methods for each such entity.

I decided to stray a bit from dogmatical REST and when I do modify I need to pass in only the entity-specific properties (like name, type etc.), but would not affect the aggregations. Thus I have endpoints like:

• post /articles - creates an article, no sections
• put /articles/{article_id} - updates basic article properties, does not affect sections
• post /articles/{article_id}/sections - creates a section in the article
• delete /articles/{article_id}/sections/{section_id} - removes the section from the article
• put /articles/{article_id}/sections/{section_id} - updates basic section properties, does not affect owning article properties, nor aggregated sections and items
• etc...

So my question is:

When I receive a modify request I get all basic properties of the element along with owning entity identifier. How can I effectively combine those with the existing relations in the database, so that I keep all of them and modify the basic properties without the need of copying over all properties one by one. Here is an example for the article-section relation.

public void modifySection(int articleId, int sectionId, Section section) {
    assert(article.owns(sectionId));
    Section dbSection = sectionDao.findOne(sectionId);
    copyOverProperties(section, dbSection); // this is the thing I do not know how to do
    sectionDao.save(dbSection);
}

Answer 1

You require hibernates session.merge(object_name);

Link : From Hibernate docs

Examples from edit functionality of our webapp :

   @Repository
    public class GroupCanvasDAOImpl implements GroupCanvasDAO {

        private final SessionFactory sessionFactory;

        @Autowired
        public GroupCanvasDAOImpl(SessionFactory sessionFactory) {
            this.sessionFactory = sessionFactory;
        }
    @Override
        public void editGroupCanvas(GroupCanvas groupCanvas) {
            Session session = this.sessionFactory.getCurrentSession();
            GroupCanvas groupCanvas1 = (GroupCanvas) session.get(GroupCanvas.class, groupCanvas.getMcanvasid());

//  Below 2 steps are not necessary if object was retrieved from DB and //then persisted back-again. If it was newly created to replace an //old-one, then the below 2 lines are needed.
    groupCanvas.setGroupAccount(groupCanvas1.getGroupAccount());
                groupCanvas.setCanvasowner(groupCanvas1.getCanvasowner());
                session.merge(groupCanvas);
                session.flush();
            }
        }
    }

If this is not what you are looking for, kindly let me know, I will delete my answer.