Oh, great! You have just saved my life. Thanks again!
Ethel
Thomas Mahler wrote:
> Hi Ethel,
>
> Ethel Emmons wrote:
> > Sorry I hit the send button too early:
> >
> > AbstractClass - contains the db open in the constructor:
> > --------------
> > constructor:
> > protected Implementation odmg = OJB.getInstance();
> > protected Database db = odmg.newDatabase();
> > //open database
> > try {
> > db.open("repository.xml", Database.OPEN_READ_WRITE);
> > } catch (ODMGException ex) {
> > ex.printStackTrace();
> > }
> > abstract public Iterator listAll();
> > abstract public boolean edit();
> > abstract public boolean delete();
> > ...
> >
> > ConcreteClass - extends AbstractClass
> > ----------------------------------------
> > - calls super() from this class' constructor that performs the db connection.
> > - uses the odmg to create Transactions, etc in the listAll(), edit(), delete()
> > methods.
> >
> > Is there any problem to this setup?
>
> seems OK for me.
>
> > Is it correct to connect everytime (by way
> > of the super() in the concreteclass constructor) listAll(), edit() or delete()
> > methods
> > are called (in separate instances - 1 web page displays all, then another web
> > page edits, etc.)
> >
>
> Yes, that's pretty OK too.
> a db.open() is not expensive and does not use any RDBMS resources.
>
> ODMG transactions do release all used resources on commit() or abort()
>
> SO there should not be any resource problems with your approach.
>
> cheers,
> Thomas
>
> > Thanks in advance.
> >
> >
> >>
> >>Ethel Emmons wrote:
> >>
> >>
> >>>In the ODMG tutorial 2 below, an application class
> >>>
> >>>performs db connect/open and passes
> >>>the odmg instance to the delete, edit, insert etc
> >>>classes.
> >>>In a web app where I have several tables to
> >>>update, insert, etc. where can I put the
> >>>connection?
> >>>Do I need to close the connection? Is the
> >>>connection always on?
> >>>Can I check if odmg and db are null before I
> >>>obtain the instance or open the db?
> >>>
> >>>Thanks,
> >>>Ethel
> >>>
> >>>public Application()
> >>>{
> >>> // get odmg facade instance
> >>> Implementation odmg = OJB.getInstance();
> >>> Database db = odmg.newDatabase();
> >>> //open database
> >>> try
> >>> {
> >>> db.open("repository.xml",
> >>>Database.OPEN_READ_WRITE);
> >>> }
> >>> catch (ODMGException ex)
> >>> {
> >>> ex.printStackTrace();
> >>> }
> >>>
> >>> useCases = new Vector();
> >>> useCases.add(new UCListAllProducts(odmg));
> >>> useCases.add(new UCEnterNewProduct(odmg));
> >>> useCases.add(new UCDeleteProduct(odmg));
> >>> useCases.add(new UCQuitApplication(odmg));
> >>>}
> >>>
> >>> --------------------------------------------------
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> >>
> >
> >
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