[OJB-developers] Re: JBOSS/OJB code

[Thomas M. <tho...@ho...>]

Hi Jesper,

Jesper Ladegaard wrote:

  > Hi again Thomas
  >
<snip>
  >
  > This is where JCA comes into the picture. The EJB server will
  > attach/detach tx-context to connection/broker resource on demand. It's
  > important there's no fixed 1-1 relationship between transaction and
  > broker. For example, it must be possible for any broker in the pool to
  > commit any active transaction. The transaction manager of the EJB
  > server only guarantees that only one transaction is active on a single
  > connection at any time.
  >

I see! Now the overall picture becomes much clearer to me.

  >
  >> Armin uses a JNDI lookup to obtain a TransactionManager instance.
  >> But we are not sure if there is an "official" way to do this.
  >>
  >
  > It's possible to obtain the TransactionManager and register a
  > javax.transaction.Synchronization with the current
  > transaction. However, this is mostly used for non-XA-aware programs
  > (i.e. client/user code) that are interrested in a callback when the
  > transaction completes.
  >
  > The official way is to enlist a XAResource with the transaction.
  > However, supporting the JCA connection contract and the connection
  > manager of the application server will take care of enlisting the
  > XAResouce for us, which is the official way of doing this in J2EE 1.3.
  >

That was the answer I was looking for!
Do you know if this mechanism is implemented in JBOSS (2.4.4 or 3.0) ?


  >
  >> If there is no standardized way for this it will be difficult to
  >> integrate OJB into different EJB Containers.
  >>
  >>
  >
  > Exactly! And this is the very reason we must support JCA, which was
  > created to solve this exact problem, plus some others also.
  >

OK !

  > [snip...]
  >
  >
  >> I think we can learn a lot from the stuff the CASTOR and Tyrex
  >> developers did in this area.
  >>
  >
  > What did they do?
  >
  > I've looked at CASTOR's code once, however it was a long time ago.
  > Their code was not nice then, but I don't know how their transaction
  > stuff works today?
  >

I don't like most of their code too. But they provide JTA and XA
implementations.
They also provide full integration with the Tyrex TransactionManager.

AFAIK that's why CASTOR integrates smoothly with JBOSS.

<snip>

  > IMO, the biggest task is for us to create a robust design for
  > integrating standard-based transaction support into OJB.
  >
  > For example, some people uses the "OBJ mode" and don't care about
  > ODMG. Others (like me) want's to use ODMG. The tx stuff should
  > intergrate and work the same for both methods.

I agree !
I would even prefer to have JTA/XA/JCA stuff only on the ODMG or JDO
level and not for the PersistenceBroker kernel.
But there are a lot of people that use the PersistenceBroker API only.
Thus they also want to have JTA/XA/JCA.

  > I mean, there seems to be a lot of confusion here. For example both
  > JBOSS integrations you've send me only works in OJB mode.
  >

I think it's OK to start with the PB to get some hands on experience.

cu,

Thomas

  > Regards Jesper
  >
  >
  >
  >
  >