I'm a novice.
Does Jersey and EJB hold the same EntityManager scope?
Should I have to pass the EntityManager to EJB for same persistence context?
The primary target usage is JTA.
#Stateless
class MyEJB {
public MyEntity find(Long id) {
...
}
#PersistenceContext;
EntityManager entityManager;
}
class MyResource {
#GET
#Path("/myentity/{id}");
public MyEntity get(#PathParam("id") final long id) {
final MyEntity found = myEjb.find(id);
// is found's state detached?
// should I have to reattach?
found.setDate(new Date());
return found;
}
#EJB
private MyEjb myEjb;
#PersistenceContext;
EntityManager entityManager;
}
Does Jersey and EJB hold the same EntityManager scope?
Should I have to pass the EntityManager to EJB for same persistence context?
I don't think that your wording is correct, but they can share the same EntityManager instance, and you have chosen the right way (through injection). Have a look at this chapter of the Java EE 6 Tutorial:
To obtain an EntityManager instance, inject the entity manager into the application component:
#PersistenceContext
EntityManager em;
So, once again, your approach is correct. With regards to the questions in the code comments: the fact that MyEntity is attached or detached, it depends on the implementation of the find method in your EJB. If you do the following, it will be attached:
public MyEntity find(Long id) {
return entityManager.find(MyEntity.class, id);
}
Finally, doing this way, if you have chosen JTA to use container managed transactions, the transactions will be automatically bounded with the natural boundaries of MyBean's methods. In order to have JTA transactions, you have to use this line in persistence.xml file:
<persistence-unit name="em" transaction-type="JTA">
Related
I am a long time Seam user who tries to move to Java EE7, JSF2.2 and CDI now.
In Seam you tend to use EntityManagers with extended scope most of the time (in the Seam Conversation Scope). You don't get any LIEs on Ajax request etc.
I am trying to do it in a similar way with Java EE7 and CDI but somehow the injected EntityManager is only transaction scoped. When I get a ajax request in the entities that were loaded before are not managed anymore.
I am using the new javax.faces.view.ViewScoped and javax.transactional.Transactional on my CDI bean.
My Producer:
#PersistenceContext(unitName = "primary", type = PersistenceContextType.EXTENDED)
private EntityManager entityManager;
#Produces
#Default
#Dependent
public EntityManager getEntityManager() {
return entityManager;
}
And my CDI bean:
#Named
#ViewScoped
#Transactional
public class TestBean implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
#Inject
EntityManager entityManager;
Logger log = Logger.getLogger(TestBean.class);
private TestEntity lastTest = null;
public void testAdd(){
TestEntity test = new TestEntity();
test.setVal("Test "+System.currentTimeMillis());
entityManager.persist(test);
entityManager.flush();
log.infov("Created test entity {0}", test);
lastTest = test;
}
public void testRead(){
List<TestEntity> test = entityManager.createQuery("select t from TestEntity t").getResultList();
for(TestEntity t: test){
log.infov("Found {0} managed {1}",t,entityManager.contains(t));
}
if(lastTest!=null){
log.infov("Last Test {0} managed {1}",lastTest,entityManager.contains(lastTest));
}
}
So when I first call testAdd() via Ajax it creates a new test entity. When I then call testRead() it gets all test entities and checks that the last created test entity is still managed (which it should if it is an EntityManager with an extended persistent context). But entityManager.contains(lastTest) always returns false.
What am I doing wrong?
I believe I can't use #PersistenceContext directly in the CDI bean. So how do I get the desired (Seam like) behaviour?
When you specify that an injected EntityManager is an extended persistence context, all object instances remain managed. Extended persistence contexts can only be used within Stateful session beans.
This is according to JBOSS documentation: https://docs.jboss.org/ejb3/app-server/tutorial/extended_pc/extended.html.
Consider packaging your insert/update/delete operations into EJBs while simple read from database can be through CDI beans. But more complex operations involving multiple reads and writes as well as transaction should be within EJBs.
I am working with JPA 2.1 (EclipseLink 2.5.1) and JBoss 7.1.
I've define very simple JPA entities:
#Entity
#Table(name="APLICACIONES_TB")
public class Aplicacion implements Serializable {
#Id
#Column(name="COD_APLICACION_V")
private long codAplicacionV;
#Column(name="APLICACION_V")
private String aplicacionV;
#OneToMany(mappedBy="aplicacion")
private Collection<Prestacion> prestaciones;
... getters and setters
}
#Entity
#Table(name="PRESTACIONES_TB")
public class Prestacion implements Serializable {
#Id
#Column(name="COD_PRESTACIONES_V")
private String codPrestacionesV;
#Column(name="DESCRIPCION_V")
private String descripcionV;
#ManyToOne(fetch=FetchType.LAZY)
#JoinColumn(name = "COD_APLICACION_V")
private Aplicacion aplicacion;
... getters and setters ...
}
I have developed a staless EJB that executes a query to obtain some "Aplicacion" entities.
#Stateless
#LocalBean
public class DocuEJB implements DocuEJBLocal
{
#PersistenceContext(name="DocuEjb", type=PersistenceContextType.TRANSACTION)
private EntityManager em;
public Prestacion getResult(String name)
{
return em.createNamedQuery("ExampleQueryName", Prestacion.class).getSingleResult();
}
}
Because I'm working with JSF 2.1 the EJB is being injected in a managed bean:
#ManagedBean(name = "ManagedBean")
#RequestScoped
public class ManagedBean
{
#EJB DocuEJB docuEjb;
public String doSomething()
{
Prestacion entity = docuEjb.getResult("egesr");
if (entity != null)
{
// It should return null because 'entity' should be detached
Aplicacion app = entity.getAplicacion();
// but 'app' entity is not null, ¿why not?
System.out.println (app.getCodAplicacionV());
}
}
}
Lazy loading is not working even when lazy loading has been defined for 'aplicacion' field on 'Prestacion' entity. The code posted before should return a NullPointerException in the next line:
System.out.println (app.getCodAplicacionV());
because 'app' entity is detached and lazy loading has been configured.
Why is not working lazy loading?
Thanks
Try to add #Transactional on doSomething(), I think that your transaction manager is not well configured.
You can see here the official spring documentation. In any case, can you add your spring configurations, so that we can better help you. :)
I don't think the behavior your encounter is abnormal or your question should state it clearly:
EJB are by default transactional
Your JSF inject an EJB, with #EJB, and I guess JBoss can create a java reference and not a proxy
The entity is being managed because the transaction is not done, it will finish when doSomething ends.
Your entity is then loaded into the EntityManager, and lazy loading works because there is a context to it.
You would call em.evict(entity) with the result your are getting, this would probably fails because the entity would not be managed any more.
In our web application, we have a facade EJB which in turn calls multiple EJBs to perform a business function. The flow is like :
SLSB facade -> invokes ejb1, ejb2, ejb 3 etc -> invoke JPA layer
In each of the ejbs in the business layer, i inject entity manager using #PersistenceContext.
A simplified version of the code is as below:
#Stateless
public class facade{
#EJB
private EJB1 ejb1;
#EJB
private EJB2 ejb2;
#EJB ejb3;
private EJB3 ejb3;
public void performAction(..) {
// invoke method on ejb1
// invoke method on ejb2
// invoke method on ejb3
}
}
#Stateless
public class EJB1 implements IEjb1 {
#PersistenceContext(unitName = "pu")
private EntityManager entityManager;
#TransactionAttribute(TransactionAttributeType.REQUIRED)
public xxxEntity insert(xxxEntity entity) throws AppException {
// code for persisting the entity
}
}
#Stateless
public class EJB2 implements IEjb2 {
#PersistenceContext(unitName = "pu")
private EntityManager entityManager;
#TransactionAttribute(TransactionAttributeType.REQUIRED)
public yyyEntity insert(yyyEntity entity) throws AppException {
// code for persisting the entity
}
}
The application is deployed on Glassfish and uses JTA transaction. Since this is container managed PC, will the same persistence context be propagated to all EJBs? Will they run in the same transaction (reusing the transaction started in EJB1)? Is there a way to verify if the same transaction is used by all EJBs (same transaction id?)
By default all ejbs (1,2,3) will participate in the one, same transaction that is started by facade ejb. You would need to define different transaction attribute for them to use different transactions (e.g. REQIRES_NEW to create new transaction).
If you really need transaction id, you could try to inject TransactionSynchronizationRegistry into your bean like this
#Resource
TransactionSynchronizationRegistry registry;
// and then get key
...
registry.getTransactionKey()
See TransactionSynchronizationRegistry and Container-Managed Transactions
How to reach the entity manager which managed the entity. I mean; suppose that i have an entity reference in the sessionBean, how can i get entityManager of this entity belonged one?
I had already tried (plz see getEntityManagerOfEntity() method) contains method of em; but it does not work.
Thx
bgrds
#Stateless(name = "MainManager", mappedName = "MainManager")
#TransactionManagement(TransactionManagementType.CONTAINER)
#Interceptors(value = { PerformanceMonitor.class, ProfileInterceptor.class })
public class MainManagerBean implements MainManager, MainManagerLocal
{
private Logger logger = Logger.getLogger(this.getClass());
#PersistenceContext(unitName = "DSApp")
private EntityManager manager;
#PersistenceContext(unitName = "DSIX")
private EntityManager integrationManager;
#Resource
SessionContext ctx;
public EntityManager getEntityManagerOfEntity(SuperEntity superEntity)
{
if (manager.contains(superEntity))
return manager;
else if (integrationManager.contains(superEntity))
return integrationManager;
return null;
}
public SuperEntity findByPrimaryKey(SuperEntity superEntity)
{
getEntityManagerOfEntity(superEntity).setFlushMode(FlushModeType.COMMIT);
return dao.findByPrimaryKey(getEntityManagerOfEntity(superEntity), superEntity);
You cannot backtrack the EntityManager from an entity using the JPA API, even when it is still managed.
What you can do, if you have references to different EMs in your bean and the entity is managed, is to check the right EM by calling em.contains(entity).
In most cases it is not really important to know, which EM has fetched an entity originally, since you can merge the entity into any persistence context and continue working with it.
i know there are masses of questions concerning a similar problem, but i didn't manage to extract a solution for my problem.
I'm trying to build a RESTful webapplication that serves data, which is provided using JPA (EclipseLink 2.4) and runs on Glassfish 3.1.2.2.
For testing i set up a guestbook database in mysql and created this all-in-one solution:
// imports etc...
// Guestbook class has #Entity
#Stateless
#Path("guestbook")
public class GuestService {
#PersistenceContext
private EntityManager em;
#GET
public Response entry() {
Guestbook entry = em.find(Guestbook.class, someid);
return Response.ok(entry.getMsg()).build();
}
}
This works perfectly well, but i want to split it in to several layers like so: REST -> DAO -> Entity
Which would transform to:
#Stateless
#Path("guestbook")
public class GuestService {
private DAO dao;
#GET
public Response entry() {
Guestbook entry = dao.getEntry(someid);
return Response.ok(entry.getMsg()).build();
}
}
// ...
public class DAO {
#PersistenceContext
private EntityManager em;
public Guestbook getEntry(int someid) {
return em.find(Guestbook.class, someid);
}
}
So this would produce a nullpointer exception when accessing the em in getEntry() because it is null.
My persistence.xml looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="..." xmlns:xsi="..." xsi:schemaLocation="...">
<persistence-unit name="guestbook" transaction-type="JTA">
<jta-data-source>jdbc/mysqldatasource</jta-data-source>
<class>model.Guestbook</class>
</persistence-unit>
</persistence>
Thanks in advance, i'm looking forward for your suggestions!
You've abstracted the DAO from GuestService just fine, but it seems that you forgot to make the DAO a #Stateless EJB and inject it in your GuestService using #EJB annotation.
#Stateless
public class DAO {
#PersistenceContext
private EntityManager em;
...
}
#Stateless
#Path("guestbook")
public class GuestService {
#EJB
private DAO dao;
...
}
I hope it helps!