Hibernate many to one not updating

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By Unidirectional relationship means only one side navigation is possible (STUDENT to UNIVERSITY in this example). Please visit My SQL installation on Local PC in case you are finding difficulties in setting up My SQL locally. Table; @Entity @Table(name = "UNIVERSITY") public class University package com.websystique.hibernate.model; import javax.persistence. We are discussing an example of Student and University relationship. Following will be the final project structure: Now let’s add/update the content mentioned in above project structure. package com.websystique.hibernate.model; import javax.persistence. We need to inform hibernate about how to connect to database, which database dialect we will be using so that hibernate can generate the instruction specific to that database. But as you’ve seen in this post, there are a few pitfalls you should avoid.association between links two tables based on a Foreign Key column so that the child table record references the Primary Key of the parent table row.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.

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As I explained in my book, many times, you are better off replacing collections with a query, which is much more flexible in terms of fetching performance.Afterward, when the collection is processed, the orphan removal action will execute the child row delete statement.Post post = new Post("First post"); Comment( new Post Comment("My first review") ); Comment( new Post Comment("My second review") ); Comment( new Post Comment("My third review") ); entity Manager.persist(post); insert into post (title, id) values (' First post', 1) insert into post_comment (post_id, review, id) values (1, ' My first review', 2) insert into post_comment (post_id, review, id) values (1, ' My second review', 3) insert into post_comment (post_id, review, id) values (1, ' My third review', 4) Even if the collection is not managed anymore, it’s rather trivial to just add/remove child entities whenever necessary.It requires just 1 additional query if you use JPQL query and Hibernate creates an INNER JOIN when you use the Hibernate then needs to perform an additional query for each of the selected entities. You can learn more about it in my free course How to find and fix n 1 select issues.,753 DEBUG SQL:92 - select item0_as id1_0_, item0_as name2_0_, item0_.fk_order as fk_order4_0_, item0_.version as version3_0_ from Item item0_ ,775 DEBUG SQL:92 - select purchaseor0_as id1_1_0_, purchaseor0_.version as version2_1_0_ from Purchase Order purchaseor0_ where purchaseor0_.id=?As for updating child objects, the dirty checking mechanism works just fine even if you don’t use a managed collection.

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