Trying to determine if NHibernate or anything else would apply for accessing a web service

Question

Here's the situation.

We have a 3rd party middleware (using SQLServer as a back-end) which we communicate with using an HTTP service link and XMLRPC-like messaging.

The service always returns a dataset as results of any commands that returns something. There is a way to pass an embedded SQL statement to the service.

So, we do not have a direct access to the database.

I'm trying to isolate this service with a layer that would simplify access. I was thinking of using an ORM like NHibernate.

Is this scenario supported by NHibernate or does NH always needs a direct access to the database?

If you have any other suggestions I'm all ears open...

Answer 1

If I understand you correctly, you're forced to use the 3rd party middle-ware - but it's not easy to deal with?

I've never used NHibernate so I can't speak for that.

Sounds like you want to add a new "service layer" (for want of a better term) on the top that's easier to deal with; the Facade pattern leaps to mind (although that's often used to bundle up a variety of different and disparate interfaces underneath a single cohesive integration point).

Basically you want to define a nice clean set of interfaces / services (in the new service layer); this new layer will then do all the hard work of interacting with the middle-ware - or with the database directly if you get the chance.

I would also suggest making this new layer into a couple of sub-parts: you don't want to go and build a new layer that's tightly coupled to the middle-ware (or database) - use Dependency Injection to isolate the outer facade from the concrete implementation, and maintain loose coupling. That way if the middle-ware disappears you won't directly impact consumers of the new service layer you've built.

Lastly, keep the Interface Segregation Principle (ISP) in mind when designing the new externally facing services.

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Answer 2

We use NHibernate and it sucks. I would not recommend it for anything. As for as I know, NHibernate does require direct access to the database (or at least you just give NHibernate a connection string like you would any other data access provider). Also, because of that, I'm pretty sure it won't know how to handle Xml datasets.