Gray's Matter
Justice Gray - North America's favorite metrosexual software consultant

I Wish These People Updated More Than Once a Year

NHibernate and Our Army At Love
Trust me, if the war stories were like this NHib would be a *lot* more widely adopted

Trust me.  I've been there, I've felt that pain, I've even debugged the NHibernate source to figure out what the heck was going on.   Please, I beg of you, tell my tale to those who ask, tell it truly...and let me be judged accordingly!  And let me tell you, this Hamlet quotation is appropriate because going through this problem will make you feel as if your mom just slept with your uncle.  Do I take NHibernate difficulties too seriously?  Maybe.

Anyway, some of you NHib rookies out there might think that if you have an enumeration, it's easy enough to just map it to an int for DB storage, like the following:

namespace J
    enum JusticeCharacteristics
        *Sassy* // This is fake code homeboy!  I can use whatever characters I LIKE!

and then in the mapping file put the following for a class using the JusticeCharacteristics in a property called "Characteristics":
<property name="Characteristics"
              column="JusticeAppeal" type="Int32" />

Bold in this case stands for THIS WAY LIES MADNESS.

You see, when you do something like this NHib tries to map back and forth between two different types - the moment you retrieve the object from the database it is marked as "dirty" and thus you will get an automatic update call every time you close the NHibernate session.  Trust me, nothing is more confusing than profiling your application and noticing that you've got random update calls firing every web request!  Certainly a very confusing and time-intensive operation, made quadruply so when a himbo like myself is trying to figure out what destruction our team has wrought! 

The solution to this problem is actually pretty simple - just use the enumeration type as the mapped type:

<property name="Characteristics" column="JusticeAppeal" type="J.JusticeCharacteristics" />

Italic in this case stands for YOU ARE NOW AN NHIBERNATE NINJA.

Given the skew of the audience that reads this blog, I fully expect:
  • 99.999999999999999% of you read this post and thought, "Thanks for sharing something completely obvious" (trust me, it won't be the first time)
  • 0.0000000000000001% freaked out and raced to their production application and now have me to thank for saving their system performance
  • one of you doesn't even know what NHibernate is, but that's okay Dad! I'll explain it to the entire family over dinner this Christmas!
[Update: For the curious, Ben Hart has an explanation of the casting issues that cause this over on his blog.]
Monday, 06 October 2008 #