@Asynchronous / Conversations / Transactions Best Practices

[chane]

I have an asynchronous method started from a SLSB. I know I can access the entitymanager in the async SLSB, is it possible to have Conversations or some type of fine grained transaction control.

My async method takes a list of records and iterates over each record. I need to have the processing for each record occur in a separate transaction. If I don't use the method in the async mode, I can use Nested Conversations for each record (at least that is what I"m trying to get working now).

It seems that I can not use the conversation context (even a new one) within an async method.

I figure there has to be a way to have control over transactions, I just don't know enough about J2EE transaction control to figure it out. Any pointers would be helpful.

Thanks,
Chris....

[gavin.king]

1. You can use standard EJB3 mechanisms for transaction demarcation, which certainly lets you have multiple transactions.

2. An asynchronous method gets a a new temporary conversation context. It cannot access the conversation context from which it was spawned.

HTH

[chane]

Thanks Gavin for the reply.

I finally figured something out. Working with new technology is always fun, even if it is a bit frustrating. I'm very new to using EJB3 - in fact I switched to using it (from tomcat/hibernate) when seam was still in it's first releases (mainly cvs at that time) because I saw the power of the framework). But now I need to go back and learn some of the things the framework manages for me.

I ended up putting

@TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)

on the class and method of the called method. Then in the method I create a new EntityManager. It's a little heavy handed but does the trick. I thought I could reuse the em for each transaction call; but couldn't figure it out. It works, just wondering if there was a better way. I tried a couple of things with UserTransaction but just didn't get it to work. Probably my fault.

Thanks again,
Chris....

@Name(value="importSale")
@Stateful
@TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public class ImportSale implements IImport {

 private EntityManagerFactory emf = null;
 private EntityManager em;

 private EntityManager txEntityManager(){
 return getEntityManagerFactory().createEntityManager();
 }

 private EntityManagerFactory getEntityManagerFactory(){
 if(emf == null) {
 try {
 return (EntityManagerFactory) Naming.getInitialContext().lookup("java:/customEntityManagerFactory");
 } catch(NamingException ne) {
 throw new IllegalArgumentException("EntityManagerFactory not found", ne);
 }
 } else {
 return emf;
 }
 }

 @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
 public void processXML(ParseFile parseFile, State state, Element record) {
 internalProcess(record);
 }

 private void internalProcess(Element record){
 try {
 em = txEntityManager();
 Contexts.getMethodContext().set("em", em); //added since DAO method access the em via
 //Contexts.lookupInAllStates(or
 // whatever the method is called)
 if(processXML(record)){
 } else {
 Transactions.setTransactionRollbackOnly();
 }
 } catch(Exception ex){
 try {
 Transactions.setTransactionRollbackOnly();
 } catch(Exception e) {
 throw new RuntimeException("Could not rollback erred record", e);
 }
 }
 }

 </snip rest>
}

[gavin.king]

Why not just use @PersistenceContext?

[chane]

Thanks - I'll give that a try. I didn't try since once I figured out how to use

@In
EntityManager em

I didn't look at this piece again and I forgot about it. Now that I've been through a more in depth learning process, I won't forget about this again (actually I probably never really learned it the first time).

Thanks for the pointer,
Chris....