Hibernate many to one not updating
As straightforward as it might be in a RDBMS, when it comes to JPA, the annotation allows you to map the Foreign Key column in the child entity mapping so that the child has an entity object reference to its parent entity.This is the most natural way of mapping a database database association, and, usually, the most efficient alternative too.SQL] - insert into Book (publishing Date, title, version, id) values (? Get more recipes like this one in my new book Hibernate Tips: More than 70 solutions to common Hibernate problems.During the collection handling phase, the Foreign Key column is updated accordingly.The same logic applies to collection state modifications, so when removing the firsts entry from the child collection: Again, the parent entity state change is executed first, which triggers the child entity update.As for updating child objects, the dirty checking mechanism works just fine even if you don’t use a managed collection.What’s nice about using a query is that you can paginate it any way you like so that, if the number of child entities grows with time, the application performance is not going to be affected.
We can apply this logic to our real world coding example that we saw in the last post. Many To One; @Entity public class Employee objects into the database in a unidirectional manner… now that we’ve changed our code around to use a bidirectional relationship, we need to change the way we persist our data. Repository; import org.springframework.transaction.annotation. Transactional; import com.howtoprogramwithjava.example.persistence. Employer; @Transactional @Repository public class Employer Dao Now the only missing piece is to show you how to actually persist data using this new bidirectional One-to-Many mapping.
If you take a look at Hibernate flush order, you’ll see that the persist action is executed before the collection elements are handled.
This way, Hibernate inserts the child records first without the Foreign Key since the child entity does not store this information.
However, there are times when mapping a collection is the right thing to do, and then you have two choices: Post post = new Post("First post"); Comments().add( new Post Comment("My first review") ); Comments().add( new Post Comment("My second review") ); Comments().add( new Post Comment("My third review") ); entity Manager.persist(post); insert into post (title, id) values ('First post', 1) 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, comments_id) values (1, 2) insert into post_post_comment (Post_id, comments_id) values (1, 3) insert into post_post_comment (Post_id, comments_id) values (1, 4) relationship, and it’s not very efficient either.
Instead of two tables, we now have three tables, so we are using more storage than necessary.