Hi Adam, I know it sounds silly as an answer, but if you avoid OO altogether for this sort of questions and SELECT COUNT(*) FROM MY_TABLE straight to the db?
d.rizzi -----Messaggio originale----- Da: Adam Hardy [mailto:[EMAIL PROTECTED]] Inviato: venerdi 31 maggio 2002 10.01 A: Struts Users Mailing List Oggetto: Re: Design Advice - Relational Databases & Java Objects There's still one question I've got about using object - relational mapping & DB access packages: what happens when I want to pull out a COUNT(*) on a grouping in the database? For instance when I want to show the number of people who've voted on an online survey, or the number of replies to a message in an online forum? How would I integrate that into the framework? Or would it have to be seperate? Re the book at http://www.object-relational.com/object-relational.html : I didn't get further than the document's table of contents, which is why I didn't see that it was a book to purchase - at a cool $1800. That's a pity. [EMAIL PROTECTED] wrote: >The link that I included in Chapter 6 actually has a >cost associated with getting at that information. I >believe it's quite severe. What these guys have done is >to compare these 13 products from every angle imaginable >and they are selling their findings. > >I mentioned that this link is beneficial only if your >project had some serious funds and you wanted to be >absolutely sure that you were picking the correct >implementation. > >Unfortunately, applications have different requirements >as well as resources available. No one solution is going >to be the perfect one for all. I would prefer to buy an >ORM solution, rather than building one, although I know >that some developers feel the opposite way. > >Chuck > > >>Oh boy, now I've got information overload! Fortunately there's a link in >>Chuck Cavaness's book to an article reviewing & comparing some of them - >>although strangely they include Forte for Java from Sun instead of JDO. >>Well, I can see what I'm going to be doing this weekend. >> >>Regards >>Adam >> >> >> >> >>Steve Muench wrote: >> >> >> >>>Oracle's J2EE Framework "Business Components for Java" >>>makes it very easy to read and write from collections >>>of values objects (sourced from the database) with >>>automatic interaction with business objects that >>>centralize your business rules, and handles the OR mapping >>>for your business objects. You pick the "shape" of >>>the data you need in your view layer, and it implements >>>all of the handlers for your value object collections >>>and optionally makes the value objects in these >>>collections transparently updateable, delegating >>>changes back through your business object layer >>>with no yucky code you have to write yourself. >>> >>>A whitepaper on all the capabilities is at: >>> >>>http://otn.oracle.com/products/jdev/htdocs/j2ee_bc4j.html >>> >>>If you've read the O'Reilly Struts book sample chapters >>>on TheServerSide.com, basically all of the Model Layer things >>>that Chuck describes in Chapter 6, "Struts Model Components" >>>as necessary pieces for your working Struts-with-Database- >>>and-Business-Logic application, the BC4J framework >>>implements for you. You basically just tell it the >>>tables you want to work with (for your BO layer), or >>>forward generate those tables from a BO object model >>>that you design, and then tell it what queries your >>>view layer needs to perform. >>> >>>You don't need to write model layer plumbing code. >>> >>> -> Don't bother writing Value Object classes >>> >>> -> Don't bother writing JDBC code for queries >>> >>> -> Don't bother writing a class to expose your >>> collections of value objects to the view layer >>> >>>All of these things are done for you. >>> >>>Plus, it works with any SQL database, not only Oracle. :-) >>> >>>I'm planning a whitepaper that specifically illustrates >>>how to couple Struts with BC4J next. >>> >>>__________________________________________________________________ >>>Steve Muench - Developer, Product Mgr, Java/XML Evangelist, Author >>>Simplify J2EE and EJB Development with BC4J >>>http://otn.oracle.com/products/jdev/htdocs/j2ee_bc4j.html >>>Building Oracle XML Apps, www.oreilly.com/catalog/orxmlapp >>>----- Original Message ----- >>>From: <[EMAIL PROTECTED]> >>>To: "Struts Users Mailing List" <[EMAIL PROTECTED]> >>>Sent: Wednesday, May 29, 2002 6:44 PM >>>Subject: Re: Design Advice - Relational Databases & Java Objects >>> >>> >>>| >>>| >>>| >>>| Adam - >>>| >>>| Have you looked at Torque from the Jakarta Tubine project? >>>| >>>| I haven't used it but have heard good things about it. It provides an >>>| ability to perform O/R mapping using an XML configuration file - and (as I >>>| understand) it creates Java files for you that implement a peristence >>>| layer. >>>| >>>| FWIW - >>>| Kevin >>>| >>>| >>>| >>>| >>>| Adam Hardy <[EMAIL PROTECTED]> on 05/29/2002 12:44:28 PM >>>| >>>| Please respond to "Struts Users Mailing List" >>>| <[EMAIL PROTECTED]> >>>| >>>| To: Struts Users Mailing List <[EMAIL PROTECTED]> >>>| cc: (bcc: Kevin Bedell/Systems/USHO/SunLife) >>>| Subject: Design Advice - Relational Databases & Java Objects >>>| >>>| >>>| Hi All, >>>| >>>| I saw this thread in the archives and I thought I'd pinch the title. >>>| I've spent this afternoon surfing the web looking at stuff on Sun, >>>| Jakarta and lots of smaller sites looking for a ready-made data access >>>| layer package but I take it there isn't an open-source one out there. >>>| >>>| Obviously I don't want to tie my data access layer to struts, so there >>>| are a few questions I've got. >>>| >>>| (1) Is it best for the data access layer to throw exceptions on error to >>>| be picked up by the business objects & then struts actions, or would it >>>| be good to use a struts-type message object and use strings in the >>>| application resources file (I'm just worried my exceptions' text would >>>| not be multi-lingual) >>>| >>>| (2) How would I get the database connection info to the data access >>>| layer? Presuming I want to set it up in struts-config.xml or as in >>>| commons-dbcp, would I then pass it in from struts actions into the >>>| business object and then into the data access layer as a parameter on >>>| each call? >>>| >>>| >>>| >>>| I've seen quite a few patterns like www.martinfowler.com and code like >>>| in Sun's Pet Store, so I think I've got a fairly good idea of what I >>>| need. The data access layer I want has got to: >>>| >>>| - take as input and return as output Data Transport Objects >>>| - allow the business objects to control transactions >>>| - use a connection pool >>>| - possibly keep the SQL statements in an external XML file >>>| - have comprehensive error handling & reporting >>>| >>>| >>>| >>>| >>>| -- >>>| To unsubscribe, e-mail: < >>>| mailto:[EMAIL PROTECTED]> >>>| For additional commands, e-mail: < >>>| mailto:[EMAIL PROTECTED]> >>>| >>>| >>>| >>>| >>>| >>>| >>>| >>>| ----------------------------------------------------------------------- ---- >>>| This e-mail message (including attachments, if any) is intended for the use >>>| of the individual or entity to which it is addressed and may contain >>>| information that is privileged, proprietary , confidential and exempt from >>>| disclosure. If you are not the intended recipient, you are notified that >>>| any dissemination, distribution or copying of this communication is >>>| strictly prohibited. If you have received this communication in error, >>>| please notify the sender and erase this e-mail message immediately. >>>| ----------------------------------------------------------------------- ---- >>>| >>>| >>>| -- >>>| To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> >>>| For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> >>>| >>>| >>> >>> >>>-- >>>To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> >>>For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> >>> >>> >>> >>> >>> >>> >> >>-- >>To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> >>For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> >> >> >> > >-- >To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> >For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> > > > > -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
