[JBoss-user] DB connection/transactions in the same J2EE transaction context.

[Karl K. <kk...@se...>]

I am hoping to find a simple resolution to this problem. I am running JBoss
2.4.3

I have a SLSB that is used for persisting business objects implemented as
simple java beans. These beans have "alter egos" as Entity Beans in the app
server. (in fact, corresponding entity beans are simply facades for a copy
of the java bean) 
The SLSB simply determines which class of Entity Bean to use, find it the
instance nessecary, and set the underlying business object to that passed
into the SLSB.

The problem comes when passing a queue of business objects where later
objects depend on side effects of the earlier objects within the database.

According to the EJB 2.0 spec "The Bean Provider can control shareability of
the connections acquired from the resource manager connection factory. By
default, connections to a resource manager are shareable across other
enterprise beans in the application that use the same resource in the same
transaction context."
"The sharing of connections to a resource manager allows the container to
optimize the use of connections and enables the container's use of local
transaction optimizations." (Section 20.4.1.1)

From this I make the assumption (bad word I know) that, under a single
(J2EE) transaction context, for the same resource, regardless of which
instance of entity bean is being operated on, a connection will be re-used
when requested more than once. I am not clear if this applies to multiple
entity bean classes, since there references are in a difference namespace,
but they do reference the same resource manager underneath everything.

The following are snippets from my ejb-jar.xml and jboss.xml files:

ejb-jar.xml

      <resource-ref>
        <res-ref-name>jdbc/jts.Connection</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
        <res-sharing-scope>Sharable</res-sharing-scope>
      </resource-ref>

jboss.xml

      <resource-ref>
        <res-ref-name>jdbc/jts.Connection</res-ref-name>
        <resource-name>jts.sempraDev</resource-name>
      </resource-ref>

    <resource-manager res-class="org.jboss.ejb.deployment.JDBCResource">
      <res-name>jts.sempraDev</res-name>
      <res-jndi-name>java:/jts.sempraDev</res-jndi-name>
    </resource-manager>

All of my beans have a trans-attribute of Required for all methods that
affect the state of objects and a default of Supports for everything else. 

What appears to be happening is that there is no guaruntee that the same db
connection will be used throughout the context of a single transaction, even
within the same entity bean class. This is causing changes to be performed
under one db transaction and subsequent changes that depend on the db side
effects of the earlier changes to be performed under a seperate db
transaction. The subsequent db transactions cannot see the earlier changes
to the db and fail, rolling back the entire set of db transactions.

When the business objects are submitted one at a time from the client
everything works fine. It is only when a queue of business objects are
submitted that the problem exists.

From what I have understood about JBoss, this part of the EJB 2.0
specification has been in place for some timel.  Correct me if I am wrong.

Any help/clarification would be appreciated.

Karl Koster
kk...@se...
Sempra Energy Trading
203-355-5182



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