fluent nhibernate - Many to Many relationship with attribute on relationship

Question

I have my code working, but I'm getting 2 extra columns in the table/ddl, to represent a Many to Many relationship, ~~but~~ with attributes (scalars) on the relationship.

I am using 1.2.0.712 (FluentNHibernate.dll) 3.1.0.4000 (NHibernate.dll)

Entities:

public partial class Employee
{
    public Employee()
    {
        CommonConstructor();
    }
    private void CommonConstructor()
    {
        this.MyEmployeeToJobTitleMatchLinks = new List<EmployeeToJobTitleMatchLink>();
    }

    public virtual Guid? EmployeeUUID { get; set; }
    public virtual byte[] TheVersionProperty { get; set; }
    public virtual string SSN { get; set; }
    public virtual string LastName { get; set; }
    public virtual string FirstName { get; set; }
    public virtual DateTime CreateDate { get; set; }
    public virtual DateTime HireDate { get; set; }

    public virtual ICollection<EmployeeToJobTitleMatchLink> MyEmployeeToJobTitleMatchLinks { get; set; }
    public virtual void AddJobTitleLink(EmployeeToJobTitleMatchLink link)
    {
        link.TheEmployee = this;
        if (!this.MyEmployeeToJobTitleMatchLinks.Contains(link))
        {
            this.MyEmployeeToJobTitleMatchLinks.Add(link);
        }

        if (!link.TheJobTitle.MyJobTitleToEmployeeMatchLinks.Contains(link))
        {
            link.TheJobTitle.MyJobTitleToEmployeeMatchLinks.Add(link);
        }
    }

    public virtual void RemoveJobTitleLink(EmployeeToJobTitleMatchLink link)
    {
        link.TheEmployee = this;
        if (this.MyEmployeeToJobTitleMatchLinks.Contains(link))
        {
            this.MyEmployeeToJobTitleMatchLinks.Remove(link);
        }

        if (link.TheJobTitle.MyJobTitleToEmployeeMatchLinks.Contains(link))
        {
            link.TheJobTitle.MyJobTitleToEmployeeMatchLinks.Remove(link);
        }
    }
}

public partial class JobTitle
{

    public JobTitle()
    {
        CommonConstructor();
    }
    private void CommonConstructor()
    {
        this.MyJobTitleToEmployeeMatchLinks = new List<EmployeeToJobTitleMatchLink>();
    }

    public virtual Guid? JobTitleUUID { get; set; }
    public virtual byte[] TheVersionProperty { get; set; }
    public virtual string JobTitleName { get; set; }
    public virtual DateTime CreateDate { get; set; }
    public virtual ICollection<EmployeeToJobTitleMatchLink> MyJobTitleToEmployeeMatchLinks { get; set; }
    public virtual void AddEmployeeLink(EmployeeToJobTitleMatchLink link)
    {
        link.TheJobTitle = this;
        if (!this.MyJobTitleToEmployeeMatchLinks.Contains(link))
        {
            this.MyJobTitleToEmployeeMatchLinks.Add(link);
        }

        if (!link.TheEmployee.MyEmployeeToJobTitleMatchLinks.Contains(link))
        {
            link.TheEmployee.MyEmployeeToJobTitleMatchLinks.Add(link);
        }

    }

    public virtual void RemoveEmployeeLink(EmployeeToJobTitleMatchLink link)
    {
        link.TheJobTitle = this;
        if (this.MyJobTitleToEmployeeMatchLinks.Contains(link))
        {
            this.MyJobTitleToEmployeeMatchLinks.Remove(link);
        }

        if (link.TheEmployee.MyEmployeeToJobTitleMatchLinks.Contains(link))
        {
            link.TheEmployee.MyEmployeeToJobTitleMatchLinks.Remove(link);
        }

    }

}

public partial class EmployeeToJobTitleMatchLink
{
    public EmployeeToJobTitleMatchLink()
    {
        //this.Id = Guid.NewGuid(); /* this works in conjuction with <generator class="assigned"></generator>   */
    }

    public virtual Guid? LinkSurrogateUUID { get; set; }

    /*  These are "scalar properties of the ~~relationship~~  */
    public virtual int PriorityRank { get; set; }
    public virtual DateTime JobStartedOnDate { get; set; }

    public virtual Employee TheEmployee { get; set; }
    public virtual JobTitle TheJobTitle { get; set; }
}

Mappings:

public class EmployeeMap : ClassMap<Employee>
{
    public EmployeeMap()
    {
        Id(x => x.EmployeeUUID).GeneratedBy.GuidComb();

        OptimisticLock.Version();
        Version(x => x.TheVersionProperty)
            .Column("MyVersionColumn")
            .Not.Nullable()
            .CustomSqlType("timestamp")
            .Generated.Always();

        Map(x => x.SSN);
        Map(x => x.LastName);
        Map(x => x.FirstName);
        Map(x => x.CreateDate);
        Map(x => x.HireDate);

        HasMany(x => x.MyEmployeeToJobTitleMatchLinks)
            .Inverse()
            .Cascade.All();
    }
}

public class JobTitleMap : ClassMap<JobTitle>
{
    public JobTitleMap()
    {
        Id(x => x.JobTitleUUID).GeneratedBy.GuidComb();

        OptimisticLock.Version();
        Version(x => x.TheVersionProperty)
            .Column("MyVersionColumn")
            .Not.Nullable()
            .CustomSqlType("timestamp")
            .Generated.Always();

        Map(x => x.JobTitleName);
        Map(x => x.CreateDate);
        HasMany(x => x.MyJobTitleToEmployeeMatchLinks)
            .Inverse()
            .Cascade.All();
    }
}

public class EmployeeToJobTitleMatchLinkMap : ClassMap<EmployeeToJobTitleMatchLink>
{
    public EmployeeToJobTitleMatchLinkMap()
    {
        Id(x => x.LinkSurrogateUUID).GeneratedBy.GuidComb();
        Map(x => x.PriorityRank);
        Map(x => x.JobStartedOnDate);
        References(x => x.TheEmployee).Column("TheEmployeeUUID").Not.Nullable();/*Bad naming convention with "The", but left here so it can be seen easily in the DDL*/
        References(x => x.TheJobTitle).Column("TheJobTitleUUID").Not.Nullable();/*Bad naming convention with "The", but left here so it can be seen easily in the DDL*/
    }
}

This works fine, but I'm getting 2 extra (nullable) columns in the ddl. They are marked with asteriks(*) below.

Select * From [dbo].[EmployeeToJobTitleMatchLink] LinkSurrogateUUID
PriorityRank JobStartedOnDate
TheEmployeeUUID
TheJobTitleUUID

*Employee_id
*JobTitle_id

I understand this is "by convention". (The names with the "_id" on them). But I don't need these columns. And I need to be able to have customized names. (TheEmployeeUUID and TheJobTitleUUID in this mock example.)

My end-game is to have:

Select * From [dbo].[EmployeeToJobTitleMatchLink] LinkSurrogateUUID (UniqueIdentifier, SurrogateKey)
PriorityRank (scalar, int) JobStartedOnDate (scalar,datetime) TheEmployeeUUID (UniqueIdentifier, FK back to dbo.Employee.EmployeeUUID ) TheJobTitleUUID (UniqueIdentifier, FK back to dbo.JobTitle.JobTitleUUID )

The attribute(s) on the ~relationship are very important to keep. (PriorityRank and JobStartedOnDate in this mock up example.)

Thanks. I'm ~so close.

EDIT:

Mappings that work:

public class EmployeeMap : ClassMap<Employee>
{
    public EmployeeMap()
    {
        Id(x => x.EmployeeUUID).GeneratedBy.GuidComb();

        OptimisticLock.Version();
        Version(x => x.TheVersionProperty)
            .Column("MyVersionColumn")
            .Not.Nullable()
            .CustomSqlType("timestamp")
            .Generated.Always();

        Map(x => x.SSN);
        Map(x => x.LastName);
        Map(x => x.FirstName);
        Map(x => x.CreateDate);
        Map(x => x.HireDate);

        HasMany(x => x.MyEmployeeToJobTitleMatchLinks)
            .Inverse()
            .Cascade.All()
            .KeyColumn("TheEmployeeUUID")
            ;

    }
}





public class JobTitleMap : ClassMap<JobTitle>
{
    public JobTitleMap()
    {
        Id(x => x.JobTitleUUID).GeneratedBy.GuidComb();

        OptimisticLock.Version();
        Version(x => x.TheVersionProperty)
            .Column("MyVersionColumn")
            .Not.Nullable()
            .CustomSqlType("timestamp")
            .Generated.Always();


        Map(x => x.JobTitleName);
        Map(x => x.CreateDate);
        HasMany(x => x.MyJobTitleToEmployeeMatchLinks)
            .Inverse()
            .Cascade.All()
            .KeyColumn("TheJobTitleUUID")
        ;   

    }
}



public class EmployeeToJobTitleMatchLinkMap : ClassMap<EmployeeToJobTitleMatchLink>
{

    public EmployeeToJobTitleMatchLinkMap()
    {
        Id(x => x.LinkSurrogateUUID).GeneratedBy.GuidComb();
        Map(x => x.PriorityRank);
        Map(x => x.JobStartedOnDate);

        References(x => x.TheEmployee).Column("TheEmployeeUUID").Not.Nullable();/*Bad naming convention with "The", but left here so it can be seen easily in the DDL*/
        References(x => x.TheJobTitle).Column("TheJobTitleUUID").Not.Nullable();/*Bad naming convention with "The", but left here so it can be seen easily in the DDL*/

    }
}

Thanks Nathan!

PS One new term I learned while googling/binging myself was

"objectified relationship"

It was in the comments area of this page: LINK1

In case that page dies sometime in the future, here is that commented pasted in:

It’s called an ‘objectified relationship’ (ref: http://www.orm.net) and in NIAM/ORM it’s typically defined as a relationship which is on itself an entity with attributes. An objectified relationship is always forming at least one m:n relationship. (From http://weblogs.asp.net/fbouma/ )

Answer 1

I think you need to add a KeyColumn("key-name") as part of the HasMany mapping to both your JobTitleMap and EmplyeeMap. This is because fluent-nhibernate is using conventions to create the FK in the EmployeeToJobTitleMatchLink table. Using KeyColumn as part of the HasMay mapping should override the convention.

Something like the following :-

public class JobTitleMap : ClassMap<JobTitle> 
{ 
    public JobTitleMap() 
    { 
        Id(x => x.JobTitleUUID).GeneratedBy.GuidComb(); 

        OptimisticLock.Version(); 
        Version(x => x.TheVersionProperty) 
            .Column("MyVersionColumn") 
            .Not.Nullable() 
            .CustomSqlType("timestamp") 
            .Generated.Always(); 

        Map(x => x.JobTitleName); 
        Map(x => x.CreateDate); 
        HasMany(x => x.MyJobTitleToEmployeeMatchLinks) 
            .Inverse() 
            .Cascade.All()
            **.KeyColumn("TheJobTitleUUID")**
    } 
}