_ctx.setInstanceFactory( _instanceFactory );
    public void begin()        throws PersistenceException    {        if ( _transaction != null )            throw new IllegalStateException( Messages.message( "jdo.txInJ2EE" ) );        if ( _ctx != null && _ctx.isOpen() )            throw new PersistenceException( Messages.message( "jdo.txInProgress" ) );        _ctx = new TransactionContextImpl( this, false );        _ctx.setLockTimeout( _lockTimeout );        _ctx.setAutoStore( _autoStore );        _ctx.setCallback( _callback );    }