Getting an EntityManager outside of the jmx bean or session

[taggat]

I have written a jmx bean that runs ok and has access to the EntityManager of my project.

However the jmx ben instantiates a thread, this thread needs access to the entity data layer.

I tried passing the EntityManager into the constructor of the thread, however when i tried to access data it complained about accessing the EntityManager

My next step was to do call Persistence.createEntityManagerFactory("db");

this works, however the call seems to create a new entity manager each time. I have it in a singleton now, so it doesn't recreated it each time, however I don't want to create it again in the first place.

Does anyone know how i get access to the EntityManager defined in the .par file.

The code

@PersistenceContext(unitName = "global")
private EntityManager em;

which works in the top level jmx bean does not seem to work in the helper classes, and i don't want to make them either jmx beans, or session beans, as i tend to instantiate quite a few of them at any one time.

[mbe1]

Hi taggat,

ich have the same problem. I dont have access to the entitymanager from a thread in a singleton. If I try to access it I get the following Exception:

javax.persistence.TransactionRequiredException: EntityManager must be access within a transaction
 at org.jboss.ejb3.entity.ManagedEntityManagerFactory.getSession(ManagedEntityManagerFactory.java:124)
 at org.jboss.ejb3.entity.InjectedEntityManager.getSession(InjectedEntityManager.java:154)
 at org.jboss.ejb3.entity.InjectedEntityManager.createQuery(InjectedEntityManager.java:67)
 at helpers.KonDisEntityManager.getByPropertyList(KonDisEntityManager.java:274)
 at taskrunnables.ImportTask.checkExistence(ImportTask.java:662)
 at taskrunnables.ImportTask.handleRow(ImportTask.java:696)
 at taskrunnables.ImportTask.run(ImportTask.java:331)

Did you solve the problem?

Does anyone know, how to get a working entitymanager into a thread running in a service bean?

Thanks Meikel

[taggat]

I have a workaround, but it is not a very nice one.

I am using 2 classes at the moment.

One that gives me an entity manager for reading only

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

public class EntityManagerUtil {

 private static EntityManagerUtil instance = new EntityManagerUtil();
 private EntityManagerFactory emf = null;

 private EntityManagerUtil()
 {
 emf = Persistence.createEntityManagerFactory("global");
 }

 public static EntityManager getEntityManager()
 {
 return instance.emf.getEntityManager();
 }

}

and one that i use to write data (Jmx bean)

import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;
import javax.persistence.FlushModeType;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;

import org.jboss.annotation.ejb.Service;

@Service(objectName = "flytxt:service=dataServer")
public class DataServer implements DataServerMBean {
 @PersistenceContext(unitName = "global")
 private EntityManager em;

 public boolean contains(Object arg0) {
 return em.contains(arg0);
 }

 public Query createNamedQuery(String arg0) {
 return em.createNamedQuery(arg0);
 }

 public Query createNativeQuery(String arg0, Class arg1) {
 return em.createNativeQuery(arg0, arg1);
 }

 public Query createNativeQuery(String arg0, String arg1) {
 return em.createNativeQuery(arg0, arg1);
 }

 public Query createNativeQuery(String arg0) {
 return em.createNativeQuery(arg0);
 }

 public Query createQuery(String arg0) {
 return em.createQuery(arg0);
 }

 public <T> T find(Class<T> arg0, Object arg1) {
 return em.find(arg0, arg1);
 }

 public void flush() {
 em.flush();
 }

 public <T> T getReference(Class<T> arg0, Object arg1) {
 return em.getReference(arg0, arg1);
 }

 public EntityTransaction getTransaction() {
 return em.getTransaction();
 }

 public boolean isOpen() {
 return em.isOpen();
 }

 public <T> T merge(T arg0) {
 return em.merge(arg0);
 }

 public void persist(Object arg0) {
 em.persist(arg0);
 }

 public void refresh(Object arg0) {
 em.refresh(arg0);
 }

 public void remove(Object arg0) {
 em.remove(arg0);
 }

 public void setFlushMode(FlushModeType arg0) {
 em.setFlushMode(arg0);
 }

 public void close() {
 // TODO Auto-generated method stub

 }

}

I know that is really horrible but it is the only way i can see to do it while not in the context of a session bean, even though i was enstantiated by a jmx bean.

[crazybuddy]

Dear Taggat,

I had the same problems as mentioned in the previous posts, and I tried your code to in my project, but failed to deploy, the error message said:

--- MBeans waiting for other MBeans ---
ObjectName: jboss.j2ee:service=EJB3,name=org.test.ejb.DataServer
State: FAILED
Reason: java.lang.ClassCastException: org.jboss.ejb3.service.ServiceContainer

--- MBEANS THAT ARE THE ROOT CAUSE OF THE PROBLEM ---
ObjectName: jboss.j2ee:service=EJB3,name=org.test.ejb.DataServer
State: FAILED
Reason: java.lang.ClassCastException: org.jboss.ejb3.service.ServiceContainer

I am afraid I must have missed something from your code, for example, the DataServerMBean interface, is it also an interface of a session bean?

Or what is the problem in my project?

Thank you for any help.

[taggat]

Crazybuddy,

the only thing i can think of is that you haven't created the DataServerMBean interface that is required to

import javax.ejb.Remote;
import javax.persistence.EntityManager;

import org.jboss.annotation.ejb.Local;
import org.jboss.annotation.ejb.Management;

@Management
@Remote
@Local
public interface DataServerMBean extends EntityManager {

}

other than that, I haven't put anything else in.


I have started to change my code so that my threads are calling a session bean to do the work, however this has the overhead of the proxies for an ejb call which i wanted to get around, especially in high speed transactions.

Taggat.