Discussion :

[aurelien.tournier]

Bonjour,

Dans le cadre de mon mémoire de fin d'études au CNAM je dois réaliser un outil d'ORM avec comme contraintes :
- L’exécution de la couche d'accès au données sur du .Net 2.0 (ASP.NET)
- Le lien doit fonctionner avec le SGBD SQL SERVER 2000 et supérieur.
Ce qui m'interdit l'utilisation de Linq.

L'outil en lui-même sera développé sous VS2010 en C# 4.0.


Je suis en train de faire un peu l'état de l'art en termes de techniques d'ORM, si vous avez des suggestions en termes de bibliographie ou en termes d'architecture applicative, elles seront le bienvenue.

[iberserk]

Pour faire un ORM "à la main" je partirais personnelement sur l'exemple "simple" (et non simpliste...) d'IBATIS

[B.AF]

Non IBatis est un mapper et pas un ORM.

Un excellent référence Française sur le sujet (et compatible .Net 2.0)
Evaluant EUSS

C'est en plus une très belle conception IMHO.

[iberserk]

Non IBatis est un mapper et pas un ORM

Un mapper objet relationnel... aussi appelé... ORM

http://www.webonweboff.com/tips/asp/orm_ibatis.aspx


Ce n'est pas parce qu'il ne génère pas automatiquement ls requètes pour les petits développeurs que ce n'est pas un ORM

[B.AF]

Autant aller à la source pour dire ça ....

The MyBatis data mapper framework makes it easier to use a relational database with object-oriented applications. MyBatis couples objects with stored procedures or SQL statements using a XML descriptor. Simplicity is the biggest advantage of the MyBatis data mapper over object relational mapping tools.

La différence fondamentale est que IBatis ne fait pas "abstraction" de la base, il spécifie un mapping d'un resultat SQL dans un modlée objet.

Quand à spécifier du SQL, la plupart des ORM existant permettent de spécifier le SQL dans le mapping ou d'utiliser du SQL en direct.

Pour la différence conceptuelle, autant regarder Fowler :

Data Mapper
A layer of Mappers (473) that moves data between objects and a database while keeping them independent of each other and the mapper itself.

Et on peut aussi lire directement la doc d'IBatis :

2.4. Is iBATIS the best choice for my project?
iBATIS is a Data Mapping tool. Its role is to map the columns of a database query (including a stored procedure) to the properties of an object. If your application is based on business objects (including Maps or IDictionary objects), then iBATIS can be a good choice. iBATIS is an even better choice when your application is layered, so that that the business layer is distinct from the user-interface layer.

Under these circumstances, another good choice would be an Object/Relational Mapping tool (OR/M tool), like NHibernate. Other products in this category are Apache ObjectRelationalBridge and Gentle.NET. An OR/M tool generates all or most of the SQL for you, either beforehand or at runtime. These products are called OR/M tools because they try to map an object graph to a relational schema.

iBATIS is not an OR/M tool. iBATIS helps you map objects to stored procedures or SQL statements. The underlying schema is irrelevant. An OR/M tool is great if you can map your objects to tables. But they are not so great if your objects are stored as a relational view rather than as a table. If you can write a statement or procedure that exposes the columns for your object, regardless of how they are stored, iBATIS can do the rest.

So, how do you decide whether to OR/M or to DataMap? As always, the best advice is to implement a representative part of your project using either approach, and then decide. But, in general, OR/M is a good thing when you

Have complete control over your database implementation

Do not have a Database Administrator or SQL guru on the team

Need to model the problem domain outside the database as an object graph.

Likewise, the best time to use a Data Mapper, like iBATIS, is when:

You do not have complete control over the database implementation, or want to continue to access a legacy database as it is being refactored.

You have database administrators or SQL gurus on the team.

The database is being used to model the problem domain, and the application's primary role is to help the client use the database model.

In the end, you have to decide what's best for your project. If a OR/M tool works better for you, that's great! If your next project has different needs, then we hope you give iBATIS another look. If iBATIS works for you now: Excellent! Join the iBATIS user mailing list if you have any questions.