6 Replies Latest reply on Nov 25, 2008 9:12 AM by wolfc

UserTransactedStartedListener is not implemented in EJB3

adrian.brock Jul 2, 2007 6:32 AM

This relates to JBCTS-599 but I can explain it without reference to that.

There is a little known feature in JavaEE called lazy transaction enlistment.
It basically works with the UserTransaction where you retrieve a connection
before starting the transaction and then ut.begin() enlists the connection.

// BMT EJB(3) method
public void doSomething()
{
 DataSource ds = ...
 Connection c = ds.getConnection(); // Not enlisted in transaction, there isn't one
 UserTransaction ut = ...
 ut.begin(); // the connection is enlisted in the transaction
}

It even works across multiple transactions

public void doSomething()
{
 DataSource ds = ...
 Connection c = ds.getConnection(); // Not enlisted in transaction, there isn't one
 UserTransaction ut = ...
 ut.begin(); // the connection is enlisted in the transaction
 ut.commit(); // connections is unenlisted
 ut.begin(); connection is enlisted in the new/different transaction
}

The problem is that EJB3 is not firing the transaction started events
from its user transaction.

Compare EJB2/EJB3:
org.jboss.ejb.EnterpriseContext/org.jboss.ejb3.tx.UserTransactionImpl


 public void begin()
 throws NotSupportedException, SystemException
 {
 TransactionManager tm = con.getTransactionManager();

 int oldTimeout = -1;
 if (tm instanceof TransactionTimeoutConfiguration)
 oldTimeout = ((TransactionTimeoutConfiguration) tm).getTransactionTimeout();

 // Set the timeout value
 tm.setTransactionTimeout(timeout);

 try
 {
 // Start the transaction
 tm.begin();

 // HERE!!!!!!!!!!!!! notify checked out connections
 if (tsl != null)
 tsl.userTransactionStarted();

 Transaction tx = tm.getTransaction();
 if (trace)
 log.trace("UserTx begin: " + tx);

In fact, if you compare the two classes you'll see that the EJB3
user transaction is incomplete in other ways (such as resetting
the transaction timeout after the begin).

1. Re: UserTransactedStartedListener is not implemented in EJB3

adrian.brock Jul 2, 2007 6:35 AM (in response to adrian.brock)

I think the way this does is pretty bad.
It requires each UserTransaction to implement a static method
to inject the transaction started listener

 //Registration for CachedConnectionManager so our UserTx can notify
 //on tx started.
 private static ServerVMClientUserTransaction.UserTransactionStartedListener tsl;

 /**
 * The <code>setUserTransactionStartedListener</code> method is called by
 * CachedConnectionManager on start and stop. The tsl is notified on
 * UserTransaction.begin so it (the CachedConnectionManager) can enroll
 * connections that are already checked out.
 *
 * @param newTsl a <code>ServerVMClientUserTransaction.UserTransactionStartedListener</code> value
 */
 public static void setUserTransactionStartedListener(ServerVMClientUserTransaction.UserTransactionStartedListener newTsl)
 {
 tsl = newTsl;
 }

Then the cached connection manager (CCM) needs to know about all listeners:


 protected void startService()
 throws Exception
 {
 tm = (TransactionManager) getServer().getAttribute(transactionManagerServiceName,
 "TransactionManager");
 TransactionSynchronizer.setTransactionManager(tm);
 ServerVMClientUserTransaction.getSingleton().registerTxStartedListener(this);
 EnterpriseContext.setUserTransactionStartedListener(this);
 }

It would be much better if the CCM had a single place to register the listener
and then each UserTransaction notified that single place of transaction start.

2. Re: UserTransactedStartedListener is not implemented in EJB3

adrian.brock Jul 2, 2007 6:37 AM (in response to adrian.brock)

NOTE: The embedded UserTransactions has the same problem.
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3. Re: UserTransactedStartedListener is not implemented in EJB3

wolfc Aug 8, 2007 10:49 AM (in response to adrian.brock)

http://jira.jboss.com/jira/browse/EJBTHREE-1028

I'll ignore the embedded user transaction for the moment. It will either be removed or deprecated.
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4. Re: UserTransactedStartedListener is not implemented in EJB3

wolfc Nov 25, 2008 6:14 AM (in response to adrian.brock)

Why is EJB2UserTransactionProvider not part of the transaction-spi?

Shouldn't the EJB2UserTransactionProvider bean define a dependency on the UserTransactionRegistry?
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5. Re: UserTransactedStartedListener is not implemented in EJB3

adrian.brock Nov 25, 2008 7:32 AM (in response to adrian.brock)
"wolfc" wrote:
Why is EJB2UserTransactionProvider not part of the transaction-spi?

Shouldn't the EJB2UserTransactionProvider bean define a dependency on the UserTransactionRegistry?

No its an incallback.

<bean name="UserTransactionRegistry" class="org.jboss.tm.usertx.UserTransactionRegistry"> THIS REGISTERS ALL USER TRANSACTION PROVIDERS  <incallback method="addProvider"/> <uncallback method="removeProvider"/> THIS REGISTERS THE LISTENERS (Currently only the CCM)  <incallback method="addListener"/> <uncallback method="removeListener"/> </bean>

That way you can remove the ejb and jca configs without having to redo
the other configurations.
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6. Re: UserTransactedStartedListener is not implemented in EJB3

wolfc Nov 25, 2008 9:12 AM (in response to adrian.brock)

So the moment UserTransactionRegistry comes online all already installed providers are also added?
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