流利的NHibernate-分离表映射

Question

Is there a way I can setup mapping for a table that doesn't have a direct reference to another table? It actually gets it's reference from another table that I do have a direct reference from.

This is what I have so far, but I'm not sure how to map the "LookupValue" in my MetaData model. It would need to map to MetaData if the [mdd].DefinitionType equals the [mdl].LookupType and the [md].DataValue equals the [mdl].LookupKey.

public class MetaData {
    public virtual long TableID { get; set; }
    public virtual MetaDataDefinition Definition { get; set; }
    public virtual int DefinitionID { get; set; }
    public virtual String DataValue { get; set; }
    public virtual MetaDataLookup LookupValue { get; set; }

    public override bool Equals(object obj) { ... }
    public over int GetHashCode() { ... }
}

public class MetaDataDefinition {
    public virtual long ID { get; set; }
    public virtual string DefinitionName { get; set; }
    public virtual string DefinitionType { get; set; }
}

public class MetaDataLookup {
    public virtual string Type { get; set; }
    public virtual string LookupKey { get; set; }
    public virtual string LookupValue { get; set; }

    public override bool Equals(object obj) { ... }
    public over int GetHashCode() { ... }
}

public class MetaDataMap : ClassMap<MetaData> {
    public MetaDataMap() {
        Table("PPOMetaData");
        CompositeId()
            .KeyProperty(x => x.TableID, "TableID")
            .KeyProperty(x => x.DefinitionID, "DefinitionID");

        References(x => x.Defintion, "DefinitionID").Not.LazyLoad().Cascade.All().Fetch.Join();
        Map(x => x.TableID);
        Map(x => x.DataValue);
    }
}
public class MetaDataDefinitionMap : ClassMap<MetaDataDefinition> {
    public MetaDataDefinitionMap() {
        Table("MetaDataDefinitions");
        Id(x => x.ID);
        Map(x => x.DefinitionName);
        Map(x => x.Type);
    }
}

public class MetaDataLookupMap : ClassMap<MetaDataLookup> {
    public MetaDataLookupMap() {
        CompositeId()
            .KeyProperty(x => x.LookupType)
            .KeyProperty(x => x.LookupKey);
        Map(x => x.LookupValue);
    }
}

Ideally, I want to have it run a query similar to this:

SELECT     data.TableID, data.DefinitionID, def.DefinitionName, data.DataValue,lu.LookupValue AS DataValue
FROM         dbo.PPOMetadata AS data 
    INNER JOIN dbo.MetaDataDefinitions AS def ON def.ID = data.DefinitionID 
    LEFT OUTER JOIN dbo.MetaDataLookup AS lu ON lu.LookupType = def.Type AND lu.LookupKey = data.DataValue
WHERE data.TableID = 1

In terms of update ability, the only thing I would ever create, update or delete would be in the MetaData table. The definitions and Lookup values would never change (at least from this part of the application). Is mapping the "MetaDataLookup" directly to the MetaData model possible? If so, can someone point me in the right direction of what I should be looking at?

Thanks!

Answer 1

I came up with a workaround that seems to be working and might take some of the complexity out. Instead of trying to handle the complex joins in a ClassMap, I built a view in Sql Server that does this for me. In my application, I built a new Model and ClassMap for the view. I haven't implemented any update logic yet, but I think I'll have the update logic work directly on the MetaData model, while the read logic (which needs everything joined together) will use the new MetaDataView model.

I'm still curious if complex joins like this are possible in Fluent NHibernate, but for now this solution seems to be working for me.