Detached objects can be later on attached to another session by calling methods like session.update(), session.saveOrUpdate() etc and become persistence objects.ģ.) Transient – These objects and collection are instance of persistence object that were never associated with session.These objects can be freely used as Data transfer objects without having any impact on your database. These objects can be freely used as Data Transfer Objects without having any impact on your database. As soon as the associated session is closed, persistence objects become detached objects and are free to use directly as data transfer objects in any application layer like business Layers, presentation layer etc.Ģ.) Detached – These objects and collection are instances of persistence objects that were associated with a session but currently not with associated with session. They are plain old java objects(POJO) and are currently associated with session. These objects synchronize their state with database depending on your flush strategy(i.e auto flush where as soon as setXXX() method is called or an item is removed from a set,list etc or define your own synchronization points with session.flush().mit() calls.) If you remove an item from persistence collections like a Set, it will be removed from database either immediately or when flush() or commit() is called depending on your flush strategy. W learned to delete a single entity using Session and Entitymanager interface and to use the JPQL query to delete a list of entities for better performance.1.) Persistent– Persistent object and collections are short lived single threaded objects, which store the persistence state. In this tutorial, we learned to delete a single entity as well as a list of entities. Query query = em.createQuery("DELETE EmployeeEntity e WHERE id IN (:ids)") And we also minimize the risk of stale first-level cache. We should flush all the pending changes to the database before executing the query so that we are making changes to the latest data. It’s often better to remove such a list of entities with a JPQL query. Executing N different SQL DELETE queries for N entities will lead to very inefficient performance. The EntityManager.remove() and Session.remove() methods are a better fit when we want to delete a single Entity but also very inefficient if we need to remove a list of entities.įor each remove() call, hibernate loads the entity, perform the lifecycle transition to REMOVED and trigger the SQL DELETE operation. : Removing a detached instance .EmployeeEntity#1 3. The above code is trying to execute a detached entity so it will throw the exception. EmployeeEntity employee = em.find(EmployeeEntity.class, 1L) In this case, this API will throw IllegalArgumentException. The delete() operation can not delete a detached entity. There is one pre-condition that the entity must be in a persistent state. The delete() API from EntityManager works almost similar to the previously discussed Session.remove().
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