RE: Sanity Check on Sharing PersistenceBroker

[McCaffrey, John G.]

you may want to create a threaded test to demonstrate concurrent usage.
What will happen when you need a transaction to span multiple tables?
Will you get "already in a tranaction" errors?
You may want to have your getBroker() method return a new instance

-----Original Message-----
From: Robert S. Sfeir [mailto:[EMAIL PROTECTED]
Sent: Wednesday, February 18, 2004 2:35 PM
To: OJB Users List
Subject: Sanity Check on Sharing PersistenceBroker


I'm integrating OJB as tightly as I can with my Struts app, and have 
written a class which implements the Struts PlugIn API.  In that class, 
when the Struts app starts up, it calls the init() method.  In that init 
method I make some calls to open a DB connection and get a 
PersistenceBroker.

Example follows:

    private final static void openDB()
  {
    try
    {
      if( getOjbDBAlias() == null || getOjbDBAlias().length() == 0 )
      {
        throw new PersistenceBrokerException( "OJB Alias Value Cannot be 
null!  Please set it properly before proceeding." );
      }
      LOGGER.log( Level.INFO, "Opening PersistenceBroker Database 
Instance." );
      setBrokerKey( new PBKey( getOjbDBAlias() ) );
      setBroker( PersistenceBrokerFactory.createPersistenceBroker( 
getBrokerKey() ) );
      LOGGER.log( Level.FINE, "PersistenceBroker Data Access Layer 
ready!" );
    }
    catch( PBFactoryException e )
    {
      LOGGER.log( Level.SEVERE, "A PBFactoryException was thrown: " + 
e.getMessage() + "\n\n" );
    }
    catch( PersistenceBrokerException e )
    {
      LOGGER.log( Level.SEVERE, "An PersistenceBrokerException Occured 
while opening the database connection: " + e.getMessage() );
    }
  }

Easy enough, now once the app is started, there is only one method in 
the class file which can be used from my DAO layer and that is getBroker().

My question is:

Am I doing this as expected, or am I going to get in trouble for using 
the same broker instance for all DAO calls?

The way I would use this persistence broker is, for example:

        broker.beginTransaction();
      final Query query = QueryFactory.newQuery( Acronym.class, crit );
      results = ( List ) broker.getCollectionByQuery( query );
      broker.commitTransaction();

I don't close the broker of course.  Am I going to hit some locking 
issues here, or is one broker enough to handle getting connections from 
DB and handle multiple simultaneous calls?

Thanks
R

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