Add Unmapped Data to NHibernate

Question

I have an object I'm trying to persist to a legacy database with NHibernate. I have all of the relevant columns from a table mapped in my domain object, but have a few fields in the table that must be populated for the structure of the legacy db.

Following a few recommendations, I created and registered an NHibernate interceptor to do this for me.

 public class CustomLineItemInterceptor : EmptyInterceptor
 {

  public override bool OnSave(object entity, object id, object[] state, string[] propertyNames, IType[] types)
  {
    var lineItem = entity as SomeCustomLineItem;

    if (lineItem == null)
    return false;


    List<string> propertyNameList = propertyNames.ToList();
    List<IType> typeList = types.ToList();
    List<object> stateList = state.ToList();

    propertyNameList.Add("Source");   // the unmapped column in the database
    typeList.Add(NHibernateUtil.String);
    stateList.Add("My Application's Name");  // the value I need to persist

    state = stateList.ToArray();
    propertyNames = propertyNameList.ToArray();
    types = typeList.ToArray();

    return true;
    }
}

I've looked at this NHibernate add unmapped column in interceptor and Unmapped Columns in NHibernate? without finding the answer.

What I'm seeing is that I the OnSave method does fire, but I get nothing stored in the database (or the SQL query generated by NHibernate).

What am I doing wrong?

Do you have access to NHProfiler (and if not why?)? What does it show you? — Shane Courtrille, Aug 25 '11 at 19:33
It shows the query executed without the new parameter added. — reallyJim, Aug 25 '11 at 20:09
Why not map this property `public virtual string Source { get { return "My Application's Name"; } private set { } }`? — dotjoe, Aug 25 '11 at 20:35
"but I get nothing stored in the database": nothing at all (no INSERT no UPDATE) or just without the non-mapped fields? — Stefan Steinegger, Aug 26 '11 at 08:50
@dotjoe Because I don't want to pollute my domain model with legacy data storage needs. — reallyJim, Aug 26 '11 at 13:26
@Stefan The insert is as per normal, as if I hadn't done anything at all. The SQL Insert contains ONLY the fields/properties that are mapped. — reallyJim, Aug 26 '11 at 13:28

score 3 · Accepted Answer · answered Aug 26 '11 at 07:49

3

there is also this approach using virtual Properties and IPropertyAccessor. I used it in one of my projects in the domain model and for me its easier to declare it once in the mapping than everywhere where i open a session, which happens in several different projects (Application, imports, ETLs, integration of other programs)

answered Aug 26 '11 at 07:49

Firo

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Ok, this is the approach I've wound up taking to get it working. I'm still curious why I can't do it via the interceptor. – reallyJim Aug 26 '11 at 14:52

score 1 · Answer 2 · edited May 23 '17 at 12:34

1

I don't know a lot about how NHibernate Interceptors work, but I wouldn't expect that changing the passed in array variables would actually change anything external to the method. In order for the new arrays to end up back outside of the method, they would need to be passed by reference (ref) parameters.

Looking at your first linked question (add unmapped column in interceptor), the first difference that jumps out is that at the end of his method, he calls the base method passing in the updated parameters (return base.OnSave(entity, id, state, propertyNames, types);). Perhaps that would help?

edited May 23 '17 at 12:34

Community

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answered Aug 26 '11 at 11:36

Chris Shaffer

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Thanks--I did miss that--but after adding back that line, I still see no change in the generated SQL Insert. – reallyJim Aug 26 '11 at 13:29

Add Unmapped Data to NHibernate

2 Answers2