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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