Notice that we are copying the title, the details and the tags while leaving the comments empty. The second one is the copy constructor as it takes a Post entity to be used as a reference for building a new instance. The first constructor is the default one which we need to add because Hibernate makes use of it when instantiating a Post entity upon fetching it directly or via a query. * Needed by Hibernate when hydrating the entity In order to achieve this goal, we need to add the following constructors in the Post entity: So, we are first fetching the previously published Post entity, and we want to use a new title while retaining some associations from the previous Post. PostClone.getTitle().replace("1st", "2nd") While a completely automated deep-cloning solution is what you might think of, in reality, we need more control over what’s to be cloned, and for this reason, it’s better to use a copy constructor approach instead like in the following example. This use case is a perfect candidate for entity cloning. Now, just like many blog platforms already offer, we want to have a feature where the user can duplicate a given Post so that it can use the previous Post as a template. PostComment comment2 = new PostComment() PostComment comment1 = new PostComment() "High-Performance Java Persistence, 1st edition"ĮntityManager.getReference(Tag.class, "Java")ĮntityManager.getReference(Tag.class, "JDBC")ĮntityManager.getReference(Tag.class, "JPA")ĮntityManager.getReference(Tag.class, "jOOQ") Now, let’s create some Tag entities first:Īnd afterward, we can create a Post entity with a PostDetails child entity and 2 PostComment associated entities: Public class PostComment Long = FetchType.LAZY) The PostComment entity has a one-to-many association with the parent Post entity, and as explained in this article, the best way to map a one-to-many table relationship with JPA and Hibernate is to use the = "post_comment")
Public class PostDetails Long = Date = "created_by")
The PostDetails has a one-to-one association with the parent Post entity, and as explained in this article, the best way to map a one-to-one table relationship with JPA and Hibernate is to use the = "post_details") The Post entity has a many-to-many association with the Tag entity, and as explained in this article, it’s better to use a Set like = "post") Getters and setters omitted for brevity Let’s assume we are using the following entities in our application: Tip - The best way to clone a JPA entity with JPA and #Hibernate /VUlz7ylNBI- Java September 8, 2018 In this article, we are going to see the best way to clone a JPA entity with JPA and Hibernate.
Have you ever wondered how to clone an entity with JPA or Hibernate? Recently, I stumbled upon this Hibernate forum question and it reminded me that this was a common requirement when working with JPA and Hibernate. So, enjoy spending your time on the things you love rather than fixing performance issues in your production system on a Saturday night! Well, Hypersistence Optimizer is that tool!Īnd it works with Spring Boot, Spring Framework, Jakarta EE, Java EE, Quarkus, or Play Framework. Follow having a tool that can automatically detect JPA and Hibernate performance issues.