ServerSession in FBS (otn sample code)

Question

I download FBS OTN sample code which version
use Toplink for manage persistence..
I have notice about some class that hold
ServerSession as it member variable
such as
////////////// FBS
package oracle.otnsamples.ibfbs.trademanagement.helper;
public class StockRateHelper {
// Toplink Server session
private ServerSession server = null;
public StockRateHelper()
throws TradeManagementEventException{
try {
// Initialize ServerSession from session.xml
server = (ServerSession) SessionManager.getManager().getSession(new XMLLoader(),
"FBSServerSession",
Thread.currentThread().getContextClassLoader());
}catch(DatabaseException dbEx) {
throw new TradeManagementEventException(" Error initializing Server Session :"+dbEx);
public void loadRates(Collection stockRates)
throws DatabaseException {
// Initialize client session
ClientSession client = server.acquireClientSession();
// Enable batch-writing [ Write Optimization ]
client.getLogin().useBatchWriting();
// Sequence pre-allocation has been enabled in project.xml with size of 50
// Get a transaction
UnitOfWork uow = client.acquireUnitOfWork();
// Register the objects with transaction
uow.registerAllObjects(stockRates);
// Commit
uow.commit();
I can deploy and run this sample (after spend a moment
for fix database schema) on OC4J10g developer preview
I have some Question
- why ServerSession not need to login before it provide ClientSession
- I don't see code for disconnect (logout) from DB , does it cause resource leak ?
thank you

Answer 1

Hi,
why ServerSession not need to login before it provide ClientSession.When we use SessionManager to retrieve sessions, in the call to getSession(), if the session is not already in the session manager's in-memory cache of sessions, the session manager creates the session and logs in. Hence we don't have to login explicitly( when using SessionMananger).
To open Session with No Login
SessionManager manager = SessionManager.getManager();
Session session = manager.getSession( new XMLLoader(), // XML Loader (sessions.xml file)
                                          "mysession", // session name
                YourApplicationClass.getClassLoader(), // classloader
                                                false, // log in session
                                               false); // refresh session
I don't see code for disconnect (logout) from DB , does it cause resource leak ?When using a three-tier architecture ( Sever-Client Session ), the client session is used to perform all operations. The client forwards all the request to the server session, which either operates on the cache or the database ( if the data is not present in the cache) . Hence the sever session is the entity that takes care of managing database resources and it has the intelligence built-in to manage the connections and resources. We don't have to worry about that. Finally when the
application goes down, we must take care of closing the server session.
We hav't explicitly closed the sever session in this application. If you require to close the server session and not
depend on the timeout mechanism, you can explicitly close the connection when the application is destroyed.
LoadDataServletCtxLsnr.java
public void contextDestroyed(ServletContextEvent sce) {
    // Close server session
I have notice about some class that hold ServerSession as it member variableAll the classes point to the same instance of SeverSession and they don't have seperate instances. There can be only one seversession for an application. The ServerSession instance is got from the Sigleton class SessionManager which manages the ServerSession.
HTH.
Regards
Elango.