Re: [CFCDev] Shared persistent objects pattern ?

[Marcantonio Silva]

Oi Aldo,   In my very  humble (and beginner) opinion, the singleton is an answer for the problem of having only one instance of a class, very usefull for example, to instantiate a single application, or maybe even to init a single facade of an app. There is an excelent article by Brendon O'Hara on the CFDJ site explaining the Singleton Pattern: http://www.sys-con.com/coldfusion/article.cfm?id=624   The problem that I need to address is how to have a repository of single objects, without having to go to the database to get them everytime I need one, and without having to instantiate them all when initializing the app.   I got the solution from the source: Martin Fowler's site has a very brief description for a patterm that does exactly what I need, here is a quote from the site:   "Objects can be added to and removed from the Repository, as they can from a simple collection of objects, and the mapping code encapsulated by the Repository will carry out the appropriate operations behind the scenes. Conceptually, a Repository encapsulates the set of objects persisted in a data store and the operations performed over them, providing a more object-oriented view of the persistence layer."   It didn't surprised me that the Pattern is called "Repository Pattern", here is the URL: http://www.martinfowler.com/eaaCatalog/repository.html   I also found the "Lazy Load" pattern, which will help me on second part of the problem, that is not having to load all my objects from the database when initializing the app, only when it's really needed for the application.   I would love to see ColdFusion implementations of both patterns, but since I didn�t find it, I will try to figure out by myself.   Regards,   Marcantonio Silva Diretor de Desenvolvimento de Produtos - Navita [EMAIL PROTECTED] www.navita.com.br Tel: +55 11 3055.2004 Cel: +55 11 7732.4907 (novo)   ----- Original Message ----- From: Aldo d'Aquino To: cfcdev@cfczone.org Sent: Friday, January 07, 2005 5:36 PM Subject: Re: [CFCDev] Shared persistent objects pattern ? Marcantonio,   maybe the Singleton Pattern could be used to grant only one instance for this shared repository.  But even in this case we need to implement the rules (in any Business Object) to check the repository first or to insert a new content in the repository.   Anything else?   Aldo Menezes d'Aquino Neto L�der de Projetos - Navita [EMAIL PROTECTED] www.navita.com.br Tel: +55 48 225.5396 Cel: +55 48 9911.5598     ----- Original Message ----- From: Marcantonio Silva To: cfcdev@cfczone.org Sent: Friday, January 07, 2005 4:11 PM Subject: [CFCDev] Shared persistent objects pattern ? Hello,   I have a problem and I don't know if there is a pattern for this, or even if this is considered a good design:   - Due to performance factors, I don't want to go to the database every time someone gets a content object, I rather prefere to "store" this object in memory so I can reuse it whenever it's invoked from the view.   - In traditional (or procedural) development, I would store an array of structures (or queryes) into an application var, and every time someone want some content, I would first try to get it from the application array, if it's not there, I would go the database, retrieve it and also insert it into the shared array.   - If someone "updates" one of the the records, I can update the table, and the application.array.structure content, so I would have both, the persistent and the "etereal" records both updated. This is all very straightforward to do in CF, I have done it before since CF 4.   I'm considering to use the gateway in Blackstone to send a message to the CFC that will update the database, so I won't even have this database access action contributing for the overall system performance.   When transporting this concept to objectland, it seems obvious to me that a design pattern must be used, both for the "shared object reposytory" and for the "message that will update the database" functions.   So comes the question: Is there any patterns out there for doing this ?     Regards, Marcantonio Silva Diretor de Desenvolvimento de Produtos - Navita [EMAIL PROTECTED] www.navita.com.br Tel: +55 11 3055.2004 Cel: +55 11 7732.4907 (novo) No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 6/1/2005 No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 6/1/2005