RE: Java and Relations DBs..

["Richards, Etienne (CAP, PTL)" <Etienne.Richards@xxxxxxxxxx>]

No, I think it is the correct thing to use container classes but you must be
realistic when looking at possible volume of data.

Let say that you have an application the lists all the customers on a web
page or on in a swing table. Then you could do one of the following things
with your container.

1. Container loads a subset and the subset is provided by the UI code.

2. Container is intelligent and maintains a block of results. As you ask for
the next customer the container will fetch the next block if required, else
it will return the entry that was already loaded as part of a previous
block.

3. Design your application to never work with a set of customers that are
too large to load at one time. So let's say the user first selects the
district before viewing the customer detail. That way you have to only show
the customers in that district (Depends on volume of data).

4. Write you container to be a wrapper around the ResultSet.

5. Use delayed instantiation (Load a minimal set of customer fields and then
only load the detail when they need to be used the first time).

It all depends.

-----Original Message-----
From: Brad Stone [mailto:brad@bvstools.com]
Sent: Wednesday, January 09, 2002 1:31 PM
To: java400-l@midrange.com
Subject: Re: Java and Relations DBs..


> Add static helper methods to your customer and or invoice
> classes that would
> perform this type of operation as a single SQL query.
> Only return the fields
> that you need in that query.

I added a new method that only does a count(*).  It's still
not that much faster.  And since I really don't need fields
in my query (only getting a count), I am not retrieving any
fields from the DB.

>
> If you are creating an object model to just be a memory
> representation of
> the database then you will have problems. The application
> should never be
> designed to load all the data into memory in order to
> perform an operation.

I'm not loading _all_ of the data, just the data that I want
to work with for each instance.  Are you saying that I
should not be using container classes?  Just working
directly with the DB?

Brad

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