On May 8, 2009, at 4:20 PM, Diego Munguia wrote:
Hi,
I have a spring-based application that connects to a local database
and to a set of remote EJBs that are deployed on a Geronimo 2.1.4
server. I'm trying to configure a transaction manager that handles
distributed transactions, because on a single service method I may
have calls to the local db and to one or more EJBs (stateless
session beans).
I don't understand your configuration. Is the spring app running in
the same geronimo 2.1.4 instance as the ejbs? If so I suspect you
don't need to do anything so long as your ejbs are not configured to
start new txs. You might possibly need to use a local ejb interface,
but I doubt it.
If your spring app is running in a different jvm than geronimo, you
will have to do some serious coding to get this to work. Although
geronimo does support importing transactions through the j2ca work
manager stuff, we don't have a full distributed transaction
implementation.
Be sure you understand the difference between 2-phase multi-resource
xa transactions that occur entirely in one vm (at least all the
XAResource implementations are in the same vm) and a true distributed
transaction in which XAResources are present in several vms; in a
typical xa implementation of a distributed tx system you'll have at
least two app server instances, one server will control the tx, and
all the other servers will be represented as XAResources to the
controlling server.
So far I've never found anyone who thinks using distributed
transactions in a production system is plausible if there is any kind
of load involved. This has driven our lack of implementation.
I've managed to configure distributed transactions in the past using
Jencks and the Geronimo TM but for local datasources (1 mysql db and
1 jackrabbit repository), this configuration required the use of a
UserTransaction object, I used spring's jndi mock functionality as I
wasn't using a j2ee server.
??? Where did the UserTransaction come from
I'm trying to replicate this conf on my current app but my problem
is that I can't get a hold of the remote UserTransaction object via
jndi. This is how I'm trying to retrieve it:
Properties properties = new Properties();
properties.put(Context.INITIAL_CONTEXT_FACTORY,
"org.apache.openejb.client.RemoteInitialContextFactory");
properties.put("java.naming.provider.url", "ejbd://localhost:
4201");
Context context = new InitialContext(properties);
context.lookup("java:comp/UserTransaction");
I'm getting this exception:
Exception in thread "main" javax.naming.NameNotFoundException: comp/
UserTransaction does not exist in the system. Check that the app
was successfully deployed.
at org.apache.openejb.client.JNDIContext.lookup(JNDIContext.java:277)
at javax.naming.InitialContext.lookup(InitialContext.java:351)
I don't understand what you want to use the UserTransaction for. To
control the entire jta tx or to control the ejb's participation in the
tx?
If the latter, even if this appeared to work, it wouldn't give you a
transaction. UserTransaction doesn't support the 2 phase commit
process you need for a multi-resource transaction. IIRC spring
doesn't make much effort to point this out.
If I go to the Geronimo console and look for UserTransaction using
the JNDI Viewer I see that there is an user transaction object under
the name java:comp/UserTransaction, so I'm guessing I'm using the
correct jndi name on my code. Plus the app successfully retrieves
the ejb proxies so I know the jndi service is up and running.
How can I retrieve the user transaction then? If there's a reason
why the user transaction is not provided for remote clients then
does anybody knows of an alternative strategy to do client-managed
transactions or any other kind of distributed transactions strategy
that allows me to keep track of my local db changes as well the ejbs
on the same transaction?
If the ejbs are on a different vm than your spring program I'd advise
you to rethink your architecture. If you really need them on
different machines make the communication asynchronous using jms.
thanks
david jencks
Thanks!
- Diego M.
