Nhibernate Fluent => hbm => SQL Schema

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What luck for rulers that men do not think.  - Adolf Hitler

More experimentation with NHibernate and we’re getting very close to Nirvana. The concept is (once again) – let’s develop our domain model first (similar to the “contract first” paradigm with SOA and WebServices) , create the mappings, and then create the database schema for the persistence mechanism (SQL Server, whatever) last.

The Fluent.NHibernate project  API allows you to map entities in NHibernate in a more expressive and more testable manner than you are typically able to do. What it does is to give you a clear path to take your POCOs (Plain Old CLR Objects) –- without any of the “glop”  attributes or dependencies – just standalone objects – and turn them into NHibernate  .hbm XML Mapping files. This is very cool because it means your objects can be marked [Serializable] and you can send them over the wire via WCF, etc. without the – “[VendorNameHere] Baggage?” getting in your way, because they don’t really have any.

Once this is accomplished, you can use the built-in NHibernate Tools classes to create an actual SQL Server (or other RDBMS) Schema SQL script to generate the database tables that mirror what your domain model represents in your POCO code.

Additionally, the Automap Classes are moving closer and closer to the ability to take care of the mapping “all at once” with a single method call. You don’t even need to persist .hbm XML mapping files; the NHibernate runtime is capable of using the generated mappings in memory.

Again, the whole point of this exercise is “Top Down” or “Objects First” – this flies against the face of the Microsoft Data-Centric approach of “Database first” LINQ-to-SQL or Entity Framework development (which is not a bad thing, because it is eminently usable) and will require further study by developers who understand the concept of “clean, unadulterated POCOs” that represent a true Domain Model approach to solving business problems for clients.

I’ll post more on this and probably write a comprehensive article to be posted on our eggheadcafe.com site complete with a downloadable VS 2008 solution.

Peter has been active on the C# and other MS newsgroups, has had samples at gotdotnet.com (now codegallery.com) that have been downloaded over 56,000 times, and has written numerous articles for eggheadcafe.com, for which he is a co-founder, and MSDNAA sites. He has also been a technical reviewer on books from Prentice Hall, Manning and other publishers. Peter was a Microsoft MVP for 10 years. Peter was born and raised in New York City, and after a stint as a jazz musician playing contrabass with the Robert Hunt Trio, migrated to sunny Florida, where he was hired as a rookie Financial Consultant at Merrill Lynch in Orlando, specializing in Corporate Services. It was at Merrill that Peter realized computers and technology were his forte. He spent his last few years at Merrill developing real – time computerized trading and and stock charting program using advanced technical analysis indicators, some of which are his own inventions. In 1997, he moved on to architect and serve as lead developer on a number of innovative web-based and middleware solutions for the healthcare and financial services industry.

Comments

  1. Anonymous6:52 AM

    Peter, Great post. I think this is definitely the way to go in regards to building applications nowadays. The one area that I see most new developers having problems with is "Where do I store my data when I need to test the app then." Trying to get them to shift paradigms in regards to that is sometimes difficult. When drafting your eggheadcafe post, be sure to include a little snippet about that! Again, great post.

    ReplyDelete
  2. Anonymous1:11 PM

    http://martinfowler.com/bliki/FirstLaw.html

    ReplyDelete
  3. peterbromberg8:27 PM

    OK, Anonymous.
    Fowler has a lot to say about cross-process ("remoting") calls in his first law, but I fail to see how this relates to NHibernate Auto-mapping.

    ReplyDelete
  4. Jonathan4:07 PM

    Martin is saying don't shuttle your domain objects across the wire. Instead you want to make calls across the wire. Better yet, you want to send "domain events" across. Once you start distributing your objects, you're in for a world of hurt.

    ReplyDelete

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