entitymanager - w3toppers.com

createEntityManager throws java.lang.NullPointerException at org.hibernate.engine.transaction.internal.jta.JtaStatusHelper.getStatus

If you’re using Hibernate 4 and trying to create a EntityManagerFactory manually (or SessionFactory) declared as <jta-datasource>, there is a property you must set on your persistence.xml called hibernate.transaction.jta.platform. For using on JBoss 7 <property name=”hibernate.transaction.jta.platform” value=”org.hibernate.service.jta.platform.internal.JBossAppServerJtaPlatform” /> I found about this property at Hibernate Docs

Injecting EntityManager Vs. EntityManagerFactory

The pros and cons of injecting EntityManagerFactory vs EntityManager are all spelled out in the Spring docs here, I’m not sure if I can improve on that. Saying that, there are some points in your question that should be cleared up. …Spring would create a new instance of a DAO for every web request… This … Read more

PersistenceUnit vs PersistenceContext

PersistenceUnit injects an EntityManagerFactory, and PersistenceContext injects an EntityManager. It’s generally better to use PersistenceContext unless you really need to manage the EntityManager lifecycle manually.

@Autowired vs @PersistenceContext for EntityManager bean

You shouldn’t use @Autowired. @PersistenceContext takes care to create a unique EntityManager for every thread. In a production application you can have multiple clients calling your application in the same time. For each call, the application creates a thread. Each thread should use its own EntityManager. Imagine what would happen if they share the same … Read more

What does EntityManager.flush do and why do I need to use it?

A call to EntityManager.flush(); will force the data to be persisted in the database immediately as EntityManager.persist() will not (depending on how the EntityManager is configured: FlushModeType (AUTO or COMMIT) by default is set to AUTO and a flush will be done automatically. But if it’s set to COMMIT the persistence of the data to … Read more

How to set the timeout period on a JPA EntityManager query

Yes, there javax.persistence.query.timeout. According JPA 2.0 specification support for this query hint is optional: Portable applications should not rely on this hint. Depending on the persistence provider and database in use, the hint may or may not be observed. Default value (in milliseconds) can be set to persistence.xml for all queries: <property name=”javax.persistence.query.timeout” value=”1000″/> Same … Read more

When should EntityManagerFactory instance be created/opened?

EntityManagerFactory instances are heavyweight objects. Each factory might maintain a metadata cache, object state cache, EntityManager pool, connection pool, and more. If your application no longer needs an EntityManagerFactory, you should close it to free these resources. When an EntityManagerFactory closes, all EntityManagers from that factory, and by extension all entities managed by those EntityManagers, … Read more

The EntityManager is closed

My solution. Before doing anything check: if (!$this->entityManager->isOpen()) { $this->entityManager = $this->entityManager->create( $this->entityManager->getConnection(), $this->entityManager->getConfiguration() ); } All entities will be saved. But it is handy for particular class or some cases. If you have some services with injected entitymanager, it still be closed.

No Persistence provider for EntityManager named X

You must move persistence.xml file to an appropriate location. More specifically, add META-INF/persistence.xml file to the root of a source folder. In this case, the following is an appropriate location: src\main\java\META-INF\persistence.xml Here are the details: (taken from the JPA spec) A persistence.xml file defines a persistence unit. The persistence.xml file is located in the META-INF … Read more

Struggling to understand EntityManager proper use

An entityManager manages a persistence context, in other word an in memory snapshot of the database state. See What is a persistence object? Every object loaded using the entityManager will be in managed state (see entity life cycle) until you close the EM. When an entity is managed, all change made to it will be … Read more