EJB3 persistence in a Tomcat webapp (ThreadLocal pattern)
When you only want to use EJB3 persistence, and not the whole EJB3 stack).
First posted to http://forum.hibernate.org/viewtopic.php?t=963478 without an answer!
In the document "Using Hibernate with Tomcat" (http://www.hibernate.org/114.html), it is suggested that you create a ServletContextListener - like the one below - where the listener initializes and closes Hibernate on deployment and undeployment of your webapp.
publicclass HibernateListenerimplements ServletContextListener{
publicvoid contextInitialized(ServletContextEvent event){
HibernateUtil.getSessionFactory();// Just call the static initializer of that class
}
publicvoid contextDestroyed(ServletContextEvent event){
HibernateUtil.getSessionFactory().close();// Free all resources
}
}
My question is: If I want to use Hibernate as an EJB3 persistence engine in a Webapp running in Tomcat, do I make a similar ServletContextListener like this:
publicclass EntityManagerListenerimplements ServletContextListener{
publicvoid contextInitialized(ServletContextEvent event){
EntityManagerUtil.getEntityManagerFactory();// Just call the static initializer of that class
}
publicvoid contextDestroyed(ServletContextEvent event){
EntityManagerUtil.getEntityManagerFactory().close();// Free all resources
}
}
publicclass EntityManagerUtil{
privatestatic EntityManagerFactory emf;
publicstaticfinal ThreadLocal<EntityManager> entitymanager =new ThreadLocal<EntityManager>();
publicstatic EntityManagerFactory getEntityManagerFactory(){
if (emf ==null){
// Create the EntityManagerFactory
emf = Persistence.createEntityManagerFactory("example");
}
return emf;
}
publicstatic EntityManager getEntityManager(){
EntityManager em = entitymanager.get();
// Create a new EntityManager
if (em ==null){
em = emf.createEntityManager();
entitymanager.set(em);
}
return em;
}
publicstaticvoid closeEntityManager(){
EntityManager em = entitymanager.get();
entitymanager.set(null);
if (em !=null) em.close();
}
}
And then in my webapp use the following code:
public Person findByName(String name){
EntityManager em = EntityManagerUtil.getEntityManager();
Query q = em.createQuery("select person from Person as person where name=:param");
q.setParameter("param", name);
Person p = (Person) q.getSingleResult();
em.close();
return p;
}
Would that be the right way to do it?
