On 3.8.2010 0:27, jsloyer wrote:
I am using WebSphere Application Server. When a request comes to a servlet,
the servlet calls my Broker Class. Inside the broker class I have the
entity manager and some transaction (below). I am running into issues where
multiple transactions are going on at once. How can I fix this?
You are using Singleton pattern to access entity manager, which means
that in a multi-threaded environment multiple threads might access the
same EM at the same time. JPA specification says this is wrong:
"An entity manager may not be shared among multiple concurrently
executing threads. Entity managers may only be accessed in a
single-threaded manner."
Since you are using JavaEE AS, look at the resource injection
capabilities (annotation @PersistenceContext), and use stateless session
beans instead of singleton (annotation @Stateless).
-Ognjen
Call from the servlet.
Broker.getInstance().getAllSegments(); //this returns a list of POJO
objects
Broker
public class Broker {
private EntityManagerFactory factory;
private EntityManager em;
private static Broker instance = new Broker();
public Broker() {
factory = Persistence.createEntityManagerFactory("myFactory",
System.getProperties());
em = factory.createEntityManager();
}
public static Broker getInstance() {
return instance;
}
.....
public List<Segment> getAllSegments() {
Query q = em.createQuery("SELECT segment FROM Segment segment
ORDER BY
segment.name");
return (List<Segment>) q.getResultList();
}
