Re: ORM or JDBC?
On 03/24/2011 06:35 AM, Michal Kleczek wrote:
Lew wrote:
Michal Kleczek wrote:
carmelo wrote:
I would like your opinion regarding the use of ORM in web applications
built with GWT. I'm a little reconsider about the ORM, and I wonder
whether it is worth to use in web applications built with GWT.
GWT is a graphical user interface library, right? What possible influence
on the choice of persistence architecture could that have?
Or am I wrong about GWT?
It depends on many things but IMHO the most important is "Do you have a
rich domain object model?" (and by "rich" I mean you have a lot of
important processing in your OO code - not just getters and setters).
If not, go back and develop one before proceeding.
Now we can proceed in the certainty that you do have one.
Right. IOW - you _always_ have an object model when programming in Java
(since it is OO language). So take an example:
Let's say the purpose of an app is to allow the user to manipulate data in a
general ledger database (managed by a RDBMS).
My object model is GWT widget library (a set of classes implementing user
interface).
Do you know of any ORM tool that will allow me to "map" one to another?
Or maybe you are saying I should design and develop _another_ class library
(an object model) and then design and develop _two_ mapping libraries (one
of them possibly based on some ORM tool) to achieve the goal?
No, but it is an antipattern to couple graphical widgets directly to the data
in the fashion you describe. Plus there is no framework such as you ask.
Widgets display values of objects, not data tables. Any framework that lets
the widgets use your data has to translate the data into an object. That's
what an ORM does, and that's what you will have to do by hand if not with a
framework.
You call that "two mapping layers". That isn't accurate. GWT is written to
use objects. You map the data into the objects that it uses, using any JPA or
other ORM tool, or via raw JDBC. That's only a single mapping.
--
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg