How to implement LastUpdate in NHibernate Entities?

Question

I'm attempting to implement an automatic LastUpdate attribute to my NHibernate entities. I thought about using database triggers and then thought it better done in NHibernate. I am following this blog post as a guide.

My domain entity is:

public class Instrument : Entity, IAuditableEntity
{
    public virtual string Name { get;  set; }
    public virtual string Symbol {get;  set;}
    public virtual ISet<BrokerInstrument> BrokerInstruments { get; set; }
    public virtual bool IsActive { get; set; }        
}

which inherits from

public abstract class Entity
{
    public virtual int Id { get; set; }
    public virtual int Version {get; private set;}
    public virtual DateTime CreateDate { get; private set; }
    public virtual DateTime UpdateDate { get; set; }
}

and here's the interface:

public interface IAuditableEntity
{
    DateTime UpdateDate { get; set; }
}

My listener class:

public class CustomUpdateEventListener : DefaultSaveEventListener
{
    protected override object PerformSaveOrUpdate(SaveOrUpdateEvent evt)
    {
        var entity = evt.Entity as IAuditableEntity;
        if (entity != null)
        {
            ProcessEntityBeforeUpdate(entity);
        }
        return base.PerformSaveOrUpdate(evt);
    }

    internal virtual void ProcessEntityBeforeUpdate(IAuditableEntity entity)
    {
        entity.UpdateDate = DateTime.Now;
    }
}

and my domain entity Instrument mapping file:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="MooDB"  namespace="MooDB" >
  <class name="MooDB.Domain.Instrument,MooDB"  table="instruments">
    <id name="Id" column="instrumentId" unsaved-value="0">
      <generator class="increment"></generator>
    </id>
    <version name="Version" column="version" type="integer" unsaved-value="0"/>
    <property name="Symbol" column="symbol" type="string" length="10" not-null="false"/>
    <property name="Name" column="`name`" type="string" length="30" not-null="false"/>
    <property name="IsActive" column="isActive" type="bool" not-null="true" />
    <set name="BrokerInstruments" table="brokerInstruments" generic="true" inverse="true">
      <key column="instrumentId" />
      <one-to-many class="MooDB.Domain.BrokerInstrument"/>
    </set>
    <property name="CreateDate" column="created" not-null="false" />
    <property name="UpdateDate" column="lastUpdated" />
  </class>
</hibernate-mapping>

My hibernate.cfg.xml:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2" >
  <session-factory>
  ... connection details snipped
    <mapping assembly="MooDB"/>
    <listener class="MooDB.Data.CustomUpdateEventListener, MooDB.Data" type="update" />
  </session-factory>
</hibernate-configuration>

My solution builds fine but I am getting a FileNotFoundException when NHibernate tries to find the listner. My references are set up correctly and I have the right using statements, so I'm not sure why NHibernate can't find it. Here's the error from the log:

2012-01-15 15:26:12,911 [TestRunnerThread] ERROR NHibernate.Util.ReflectHelper [(null)] - Could not load type MooDB.Data.CustomUpdateEventListener, MooDB.Data. System.IO.FileNotFoundException: Could not load file or assembly 'MooDB.Data' or one of its dependencies. The system cannot find the file specified. File name: 'MooDB.Data'

Do you know what could be wrong?

Edit: I'm now getting the following SqlTypeException:

2012-01-15 17:06:37,302 [TestRunnerThread] ERROR NHibernate.AdoNet.AbstractBatcher [(null)] - Could not execute command: UPDATE instruments SET version = @p0, symbol = @p1, [name] = @p2, isActive = @p3, created = @p4, lastUpdated = @p5 WHERE instrumentId = @p6 AND version = @p7 System.Data.SqlTypes.SqlTypeException: SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.

It seems that the code entity.UpdateDate = DateTime.Now; in ProcessEntityBeforeUpdate is not being run for some reason. Any ideas?

It's the namespace of my Data project. See this post for a structure of my project: http://stackoverflow.com/questions/8853519/how-should-i-organize-my-c-sharp-solution — Mark Allison, Jan 15 '12 at 16:39
Try placing a brakepoint in the listener, Does it stop there? — gdoron, Jan 15 '12 at 17:21
@gdoron, no it doesn't stop there. In my Update method, when I run `_session.SaveOrUpdate(entity)` I get this in my log> `2012-01-15 17:34:10,022 [TestRunnerThread] DEBUG NHibernate.Event.Default.DefaultSaveOrUpdateEventListener [(null)] - ignoring persistent instance ` — Mark Allison, Jan 15 '12 at 17:35
On the next line in my logs, I get `2012-01-15 17:34:10,022 [TestRunnerThread] DEBUG NHibernate.Event.Default.DefaultSaveOrUpdateEventListener [(null)] - object already associated with session: [MooDB.Domain.Instrument#1] ` I get my error when I call `.Flush()` — Mark Allison, Jan 15 '12 at 17:36

score 1 · Accepted Answer · answered Jan 15 '12 at 17:01

1

It's looks like your's assembly name is wrong. try this:

<listener class="MooDB.Data.CustomUpdateEventListener, MooDB" type="update" />

answered Jan 15 '12 at 17:01

gdoron

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That was it thanks, I changed to `class="MooDB.Data.CustomUpdateEventListener, Data"` Please see my edit for a further issue. – Mark Allison Jan 15 '12 at 17:08
@MarkAllison, What was the problem of the `type` and what type...? – gdoron Jan 15 '12 at 18:13
I had `type="update"` and I changed it to `type="save-update"` in hibernate.cfg.xml. However now I have an issue with `Save`... – Mark Allison Jan 15 '12 at 18:45
I have a follow-up question here http://stackoverflow.com/questions/8872542/how-to-configure-nhibernate-event-listeners-for-update-and-save – Mark Allison Jan 15 '12 at 19:17

How to implement LastUpdate in NHibernate Entities?

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